NODULAR LESIONS OF THE SKIN
A cutaneous nodule is a
circumscribed relief of the skin, which persists for
weeks. In this chapter are included the skin disorders
characterized by nodular infiltration of the dermis, both
of the inflammatory (granuloma) and proliferative type.
We will initially treat the inflammatory or granulomatous
nodular lesions, which are caused by infectious agents
-viruses, bacteria and fungi-, by infestation
-leishmaniasis, scabies and tick bite, by other agents
-post-traumatic granuloma and granuloma gluteale
infantum- or by not defined causes -annular granuloma,
granuloma faciale and sarcoidosis-.
We are starting from chronic
granulomatous disease (CGD). Although caused by
infectious agents, CGD is determined by an inherited
deficiency of bactericidal function of phagocytes.
Chronic granulomatous disease is usually transmitted by a
recessive x-linked trait. Therefore, it prevails in the
male born to a female carrier of the gene defect. The
gene has been mapped to the Xp21.1 region of the X
chromosome. There are also forms transmitted with an
autosomal recessive trait. The consequent gene defect
consists in the lack of a b-cytochrome. The latter plays
a significant role in oxidase system, which is
responsible for the burst of respiratory oxidative
activity of phagocytes. The defect is present in the
polymorphonuclear leukocytes, eosinophils and monocytes.
The bacterial phagocytosis is usually associated with a
burst of the oxidative respiratory activity, which
release hydrogen peroxide and unstable intermediate
radicals with bactericidal activity such as singlet
oxigen hydroxil radicals. Hydrogen peroxide combining
with chloride and iodide ions, gives raise to oxyhalides,
which play a significant role in the bactericidal
activity. The reaction is catalysed by myeloperoxidase.
The accumulation of living bacteria in the phagocytes
leads to the formation of granulomas in the skin, lymph
nodes, lungs, liver, intestine and bone marrow.
The easiest laboratory diagnosis is made by the nitroblue
tetrazolium dye test. The latter is based on the ability
of polymorphonuclear leukocytes of reducing during the
phagocytosis the oxidate and colorless tetrazolium
nitroblue to blue formazan.
From a clinical point of view, the onset of the disorder
is early, usually in the first two years, and
characterized by neonatal pustulosis and nonspecific,
impetiginized, periorificial lesions, usually on the face
||Folliculitis of the scalp,
perianal abscesses and suppurating perionyxis are
often present. All these infectious disorders are
due to Staphylococcus aureus or opportunistic
bacteria such as Nocardia, Legionella or
Besides the skin lesions, which often are the
first sign of CGD, are also present short
stature, recurrent pneumonia with its
characteristic radiological finding of
encapsulating pneumonia and gastrointestinal
infections, with characteristic obstructive
The prognosis is variable and positively
influenced by a continuous antibiotic
(trimethoprim-sulphamethoxazole) and antimycotic
treatment and by a careful cutaneous antisepsis.
Interferon gamma and bone marrow transplantation
can be also useful.
|Fig. 725: Chronic
disease with nodular lesions of the face.
Some virus infections can
be sometimes characterized by a granulomatous
appearance, due to coexisting particular
disorders. Herpes simplex in subjects suffering from leukemia
can be for example characterized by a
granulomatous appearance (Fig. 726, 727).
due to a pox virus. The latter is responsible for
cows mastitis. We are dealing with a
professional disease affecting milkers. The
disease is characterized by an inflammatory
granulomatous lesion of the hands (Fig. 728),
which later undergoes hemorrhagic necrosis and
herpes simplex in a subject
The great chronic infectious
diseases played a significant role in the history of
dermatology. Although less frequent and fightening as
compared with the past, these disorders are still
responsible for a prejudicial interpretation of the
cutaneous lesions, especially of those lesions persisting
for a long time on exposed and visible sites. In the past
these disease were characterized by contagious lesions in
exposed areas and by a severe, sometimes lethal
prognosis. Today still persists a prejudicial fear of
these lesions, which extended in the popular phantasy to
all the dermatological lesions persisting on exposed
sites. This is why every persisting and visible skin
lesion raises in people who observe it the fear of
contagion and therefore repulsion towards the affected
subject. In their turn the affected people, besides
suffering from the variable consequences of the
dermatological disorders, must also face this further
sufference, namely the feeling of being prejudicially
rejected, only because of a visible and persisting skin
lesion, even though the latter is not contagious.
Therefore, it is not strange that a persisting and
visible shin disorder is considered a misfortune, both in
religious myth -as in the case of Job- and art.
As important consequence of this prejudice, physicians
who diagnose a non contagious skin disorder, should with
their words and gestures reassure the patient and his/her
parents that they are not dealing with a contagious
disease, even though the relevant question is not raised.
Fig. 730: Scrofuloderma with
tous lesions and with evident submandibular
tubercolosis. Scrofuloderma (Fig. 730) is most frequently
diagnosed in childhood in the developed
countries. We are dealing with a secondary
tuberculosis, in which the skin is affected by
contiguity from an underlying tubercular lesion,
usually an affected cervical lymph node.
The characteristic lesion is a 2-4 cm in size,
inflammatory, reddish, tense (Fig. 731) nodule,
which progressively gets more tense till being
ulcerated (Fig. 732). The underlying lymph node
is not always clinically evident. After the
ulceration fistolous passages develop, often
communicating each other and exudating. Later on,
the reparative fibrous process starts, eventually
leading to an often disfigurating, irregular
The pathological examination, which
is rarely performed in this disorder, initially shows a
typical tubercular granuloma, consisting of epithelioid
cells with Langhans giant cells in the middle and
lymphomononuclear cells at the periphery. Later on, the
center of the lesions undergoes caseous necrosis and
eventually a fibrosclerotic scar occurs.
The diagnosis is confirmed by a positive intradermal test
with tuberculin, by showing acid-fast bacilli in the
microscopic examination and, above all, by positive
cultures in Petragnani medium. When available, polymerase
chain reaction can identify even small contents of
mycobacterial DNA and confirm the diagnosis in a few
vulgaris is another form
of post-primary tuberculosis, arising in subjects with
hypersensitivity towards mycobacterium tuberculosis.
Today, it is rare especially in childhood.
The lesions usually start on the face, especially around
the nose. The skin lesions are characterized by
erythematous plaques with small, soft, micronodules,
which can be easily depressed. On diascopy, the plaque
acquires a characteristic yellowish color. The plaques
can get ulcerated and give raise to wasting scars.
The clinical diagnosis is confirmed by a strongly
positive intradermal test and in some cases by the
pathological findings. Rarely the cultures grow
skin tuberculosis is a
more rare form of cutaneous tuberculosis but
characteristic of childhood. It is due to cutaneous
inoculation of M. tuberculosis in a subject, who had not
contact with this agent.
We are dealing with a nodular and ulcerative lesion
mainly affecting the skin of the face (Fig. 729), with
frequent satellite adenopathy.
729: Primary cutaneous tubercu-
losis in a 1-year-old boy.
slowly regresses in many months and can develop
into a form of post-primary tuberculosis. On
light microscopy, an acute infiltrate of
polymorphonuclear leukocytes can be initially
observed. With time, the infiltrate acquires the
characteristics of the tubercular granuloma with
disappearance of the bacilli. As other forms of
tuberculosis, primary tuberculosis of the skin
can be associated to erythema nodosum.
The appearance, although exceptional, of erythema
nodosum in a child should always raise the
suspicion of tuberculosis.
The treatment is based on the use of isoniazid
(15 mg/kg per day, max 300 mg), rifampicin (10
mg/kg per day) and pyrazinamide (30 mg/kg per
day) for the first 2 months, then isoniazid and
rifampicin twice a week for the following 4
Syphilis. Granulomatous syphilitic lesions can be
observed in the primary and tertiary phase. In the child
the tertiary form does not practically exist and the
primary form exists only as a consequence of sexual abuse
in the peripuberal period.
We are briefly mentioning congenital syphilis, which is
the most frequent form in childhood, although its
prevalence significantly changes with time and in various
countries. For instance, in 1996, 56 cases of congenital
syphilis were recorded in New York, whereas three years
later the cases were more than 1,000.
A pregnant woman with recent syphilis infects the fetus
through the placenta, starting from the fourth month of
fetal life. When the mother is affected by latent
syphilis, the probability of infecting the fetus
significantly decreases. Besides the cases of negligence,
the infection can be due to serological negativity. The
latter can be due to a late contagion or to excessive
amounts of antibodies, as in secondary syphilis.
The infection of the fetus is often massive. This is why
an abortion can occur. Fetal congenital syphilis is
characterized by late -after the fourth month- and
repeated abortions and by hydramnios. Natimortality and
perinatal mortality are also expression of a massive
infection of the fetus. When the infection is less
massive, because for instance the contagion occurred
late, prematurity or late appearance, even after years,
of the clinical signs can occur.
Therefore, a precocious congenital syphilis corresponding
to the secondary period of the acquired syphilis and a
late congenital syphilis corresponding to the tertiary
period, are usually described.
||Precocious congenital syphilis. Due to the generalized infection,
whatever organ can be affected, starting from the
placenta, which is usually hypertrophic. The skin
is affected by a papular coppery red rash. The
lesions are usually annular (Fig. 735, 736) and
can involve the perianal -perianal condylomata
lata- (Fig. 735) or palmar and plantar region.
The latter localization is characterized by a
bullous appearance (pemphigus syphiliticus). When
the blisters break, the papular, infiltrated and
annular lesions appear (Fig. 736). The lesions
contain a lot of spirochetes, which can be shown
on dark field microscopy.
The lesions of the nasal mucosa (luetic coryza)
are characterized by sero-hematic exudation.
Perianal papular lesions (condylomata lata)
of the long bones is another characteristic sign.
The transition area between the cartilage and the
bone appears broad and irregular. From a clinical
point of view, there is a painful tumefaction,
which can lead to the so-called Parrots
pseudoparalysis (Fig. 733).
Anemia, enlargement of the liver and spleen,
nephrosis, interstitial pneumonia, hydrocephalus,
neurological, ocular and whatever organ
manifestations can also occur.
733: Congenital syphilis: Parrot pseudoparalysis
A falsely negative serology in the
newborn (for instance excess of 7S IgG of maternal origin
in the FTA-IgM test) can delay the diagnosis and
More frequent is the problem of the falsely positive
luetic reactions, which are due to the passage through
the placenta of maternal 7S IgG antibodies. The
differential diagnosis of this condition is extremely
important. Treating all the newborns with positive VDRL
would be simple. However, from a psychological point of
view, in this case the mother could feel unfairly
responsible of the infection of her child. On the other
hand, physicians should not ignore that at birth,
although rarely, the clinical features of congenital
syphilis may lack and appear later, even after many
years. It is important to remember that the titer of
passively transmitted antibodies rapidly decreases in the
newborn till annulling themselves within the third month.
When quantitatively testing in the same session of the
same laboratory the serum of the mother and that one of
her child, the antibody titer of the child, in case of
transmitted positivity, is never higher than that one of
the mother and significantly decreases after 1 month.
More specific tests such as FTA/IgM are not available in
all the laboratories and are not free from false positive
and false negative results. Increased IgM in the newborn
and aspecific inflammation indexes can confirm the
suspicion of congenital syphilis.
A very important criterion derives from the mother
history. When the mother was opportunely treated, the
newborn is unlikely affected by congenital syphilis. In
conclusion, treating a newborn with transmitted
positivity is not right, unless in particular environment
conditions the newborn cannot be opportunely monitored.
Leprosy. Leprosy is a granulomatous infectious
disease due to Mycobacterium leprae. The latter can be
shown in the affected tissue (Fig. 739). Skin and nerves
are mainly affected. The contagion occurs following
prolonged contact in predisposed subjects. This is why
children are more often affected than the partner. The
source of the disease is usually a relative with a not
yet diagnosed lepromatous form of the disease and with a
nasal secretion rich in bacilli. The contagion usually
occurs in childhood.
The clinical features of the disease are due to the
immunological reactivity and peripheral nerve damage.
Tuberculoid and lepromatous lepra are the two ends of the
clinical spectrum of the disease.
In lepromatous leprosy the specific cell-mediated
immunity against the mycobacterium is depressed, leading
to a significant multiplication and diffusion of bacilli
in the tissues, whereas the lack of activated lymphocytes
leads to a less evident neurological compromission.
On the other hand, in tuberculoid leprosy the cell
mediated reactivity is evident, leading to localize the
disease in a few sites and to a significant neurological
compromission due to the lymphocyte infiltrate. The
neurological compromission is evident both in the skin
and in the peripheral nerves.
In the skin the compromission of the sensory and
autonomic nerves is responsible for the loss of
sensitivity and sweating in the affected areas. The more
superficial, peripheral nerve trunks and those ones
running in fibrous-osseous tunnels are more easily
compressed by the lympho-cyte infiltrate.
As a consequence of the compression, anesthesia, muscle
weakness and contractures appear. Anesthesia is in turn
responsible for burns, tissue necrosis and ulcers.
Leprosy reaction and erythema nodosum are a consequence
of the altered immunological reactivity. Erythema nodosum
is due to the deposition of immune complexes.
From a clinical point of view, the first sign is usually
an area of insensitivity of the skin. The latter can be
shown level with a hypopigmented area or it can be
suspected and then shown level with burns or traumatic
ulcers, which cannot be explained unless a defect of
sensitivity is demonstrated.
As above mentioned, the two polar forms of leprosy are
tuberculoid and lepromatous lepra. Borderline leprosy has
leprosy the lesions are
few and characterized by an erythematous plaque with
hypopigmented, insensible center. In the subject with
dark skin erythema may lack. At the periphery of the
plaque a thickened nerve can be sometimes palpated. The
nerve can be only affected without involvement of the
Fig. 738: Lepromatous lepra in a
||Lepromatous leprosy. It is characterized by mucous
signs, essentially exudating and hemorrhagic
rhinitis, and cutaneous signs such as
erythematous and hypopigmented macules, papules,
nodules (Fig. 738) and diffuse infiltration of
the skin. In this form lepromatous reactions are
frequent. The latter are characterized by general
vasculitis, and symptoms, which are probably due
to immune complex vasculitis, and cutaneous
nodules, mainly of the face and extensor aspect
of the arms, which can suppurate and ulcerate.
The nervous involvement in leprosy
mainly affects the sensory function. In the severe forms
the autonomic nervous system is consistently affected.
Rarely, the motor component is exclusively affected.
Ocular lesions till blindness are not exceptional in
The diagnosis of leprosy is clinical, thanks to the
presence of anesthesia, nerve thickening and typical
cutaneous lesions, and biological by showing Hansen
bacilli in the smears from the nose and cutaneous
The treatment of leprosy is essentially based on
rifampicin, dapsone and clofazimine. The paucibacillary
patients are treated with two associated drugs
(rifampicin and dapsone) for six months. Multibacillary
patients are treated with three associated drugs
(rifampicin, dapsone and clofazimine) for two years.
After withdrawing treatment, paucibacillary patients are
monitored for two years, whereas multibacillary patients
for five years.
The treatment of the leprosy reactions is based on the
use of corticosteroids and in the mild cases of
We are treating in this chapter
granulomatous candidiasis, kerion and sporotrichosis.
|Granulomatous candidiasis. It is one of the most severe forms
of chronic mucocutaneous candidiasis. Unlike the
other three forms, which are transmitted by an
autosmoal dominant or recessive trait, this form
probably is not inherited. It is particularly
severe, because characterized by esophageal
involvement, other infections and
From a dermatological point of view,
granulomatous candidiasis is characterized by
hyperkeratotic and nodular lesions, which are
mainly located on the scalp. Granulomata are
probably due to the accumulation of
polymorphonuclear leukocytes, which are not able
to destroy candida elements.
The cutaneous lesions are very widespread and the
nail compromission is marked (Fig. 740, 741).
The prognosis of granulomatous candidiasis, as
well that one of the other forms of chronic
muco-cutaneous candidiasis changed with
ketoconazole and other systemic anti-mycotic
drugs. The milder forms sometimes regress after
only one cycle of these drugs and the regression
is sometimes definitive. More often more cycles
of the drugs should be administered.
with severe nail involve-
There are also granulo-
matous lesions on the face
Kerion. Kerion is usually described as an
inflammatory ringworm, whereas the term non inflammatory
ringworm is reserved to tonsurating ringworms. Really,
inflammation is also present in tonsurating ringworm, as
shown by its scaling. Kerion is characterized by a severe
granulomatous inflammation, which is followed by
suppuration of the lesions. The inflammation is so marked
that leads to the regression of the mycotic lesions, even
without a specific treatment. As a matter of fact, kerion
was the only ringworm regressing before puberty when
griseofulvin had not yet appeared. In that time
tonsurating worms went on till puberty, if children were
not treated with aggressive therapy, such as thallium
acetate or roentgen depilation, which were associated
with severe side effects, till death.
worm (kerion) localized on
the right parietal and nuchal
745) is caused by the same agents, which are
responsible for tonsurating ringworm, therefore
today by microsporon canis in most cases. The
different clinical feature is therefore due to
the individual reaction of the subject.
From a clinical point of view, the lesions appear
intensely erythematous and infiltrated,
eventually giving raise to a granulomatous
plaque, which is clearly defined and raised for
1-2 cm. The suppurative process follows, leading
to discharge of pus, spontaneously and at
palpation. Often, regional adenopathy coexists
and superimposed bacterial infections are
Constitutional symptoms and intense, spontaneous
and at palpation, pain are present. After a
couple of months, even without a specific
antimycotic treatment, the lesions tend to
spontaneously regress. The hairs lack almost
completely in the inflammatory areas.
After the regression of the
inflammatory lesions, the hairs only partially regrow and
remain more sparse in the affected areas.
The diagnosis by fresh mycological examination is more
difficult than in tonsurating ringworms, due to the lack
of broken hairs and the presence of pus.
The treatment of choice is griseofulvin at a dose of 15
mg/kg per day for 30 days. If the syrup is not available,
the pills can be pulverized with a spoonful and
administered after the meals. At least initially, a
systemic antibiotic treatment is often associated to the
antimycotic drugs. It is also useful an antiinflammatory
local treatment with wet compresses soaked in weak
disinfectants at environment temperature.
According the Italian law, infected children can attend
the school provided they wear a hat. However, it is
better to avoid the suspicious looks of friends and above
all of adults, with their fear of contagion. Children
could again attend the school when acceptable from an
esthetic point of view.
Fig. 742: Lymphatic
||Sporotrichosis. Sporothrichosis is a mycotic
infection with a particular tropism for the lymph
structures. It is caused by Sporotrichum
The disease is characterized by a particular
geographical distribution, preferring the
temperate and tropical areas. The fungus
penetrates into the skin usually of the lower
limbs through often traumatic breaks.
Sporotrichosis is more frequent in male adults,
who are professionally exposed such as farmers
and miners. However, it can also affect children
(Fig. 742, 743), especially when they walk
barefoot on the ground. Once entered the skin,
the fungus causes a dermal and subcutaneous
granulomatous reaction, with tendency to the
According to the individual reaction, the fungus
can remain in the site of penetration, be
transmitted along the lymphatic structures till
the regional lymph nodes or rarely give raise to
a systemic disease.
The lymphatic form is more
frequent, starting with a nodular lesion, which is
usually localized on a leg or foot. The initial lesion,
when is not diagnosed and precociously treated, undergoes
colliquation necrosis and ulceration. Later on, the
involvement of the lymphatic vessels is betrayed by the
hardening of the draining lymphatic vessels and then by
the appearance on the same vessels of other granulomatous
lesions, which then tend to be colliquated and ulcerated.
When the disease is not treated, the lymph nodes can be
affected and then ulcerated, whereas the previous lesions
can spontaneously regress.
In the more rare localized form, the disease, probably
due to a high degree of immunological resistance of the
patient, remains localized in the site of primary
inoculation, running the same stages already described in
the lymphatic form, till the possible spontaneous
On the other hand, the systemic form, which is probably
due to anergy of the patient, for instance alcoholic, is
characterized by disseminated lesions of the lungs,
joints, meninges and skin.
Cutaneous sporotrichosis should be mainly differentiated
by mycobacteriosis and leishmaniasis. The history
(profession and origin of the patient), the smear from
the lesions (leishmaniasis) and the culture
(mycobacteriosis) make usually easy the differential
diagnosis. Cultures on Sabouraud medium grow whitish, wet
and superficially rough colonies, which progressively
turn to brownish, chocolate-like color.
The treatment is based on the use of potassium iodide in
saturated solution (potassium iodide 10 g, distilled
water 10 ml). Initially, 3-5 drops of the solution, 3
times a day, far away from the meals, are given. The dose
is then daily increased till to 30-50 drops 3 times a
day. The treatment should be continued for 20-30 days,
till the healing of the lesions.
Instead of potassium iodide, itrakonazole, at a dosage of
100-200 mg per day in adults (3 mg/kg per day in
children) can be given for the same period of time.
Among the agents responsible of
granulomatous reactions of the skin, we are treating
leishmaniasis, scabies and tick bite.
Leishmaniasis. The disease is caused by flagellate
protozoa of the genus Leishmania, which undergo a
development cycle in the intestine of insects of the
genus Phlebotomus in Europe.
In the vertebrate host the amastigote (lacking the
flagellum) form is found into the cells of the
reticulo-endothelial system as round, 2-3m in diameter
bodies, which characteristically present two eccentric,
basophilic nuclei (the smaller is kinetoplast).
The infection is usually transmitted through the sting of
the Phlebotomus. Vertebrates are the habitual host and
the reservoir of the infestation. Their life habits and
the biological cycle of the Phlebotomus influence the
distribution of the disease in particular geographical
Humans, which are usually accidental hosts, can present
lesions on the skin or in internal organs. Both the
localizations are usually due to the same parasite.
However, cutaneous and visceral leishmaniasis are
unlikely shown in the same subject.
Cutaneous leishmaniasis is characterized by a nodular
granulomatous lesion, which affects exposed areas, more
frequently in children (Fig. 746).
||The nodule is
firm and elastic with a characteristic central
area of softening, due to a necrotic process. The
softening area is usually appreciated when a
scrap of tissue is removed with the spoonful to
show the parasite. The central area tends to get
ulcerated and covered by a crust. After many
months the lesion tends to regress with fibrosis.
This is why leishmaniasis is called "one
The lesion can be larger and form a plaque (Fig.
747) or less infiltrated (Fig. 748) and
yellow-orange (lupoid leishmaniasis).
|Fig. 746: Nodular
The diagnosis is usually clinically
suspected taking into account the clinical features and
the origin of the patient.
The clinical diagnosis is usually confirmed by showing
the parasite within the lesions. A scrap of tissue is
removed from the lesion, smeared on a slide, fixed with
methanol and finally colored with Giemsa. In the
granulomatous form parasites are usually shown rather
easily, inside the histiocytes (Fig. 750) or free in the
paucibacillary forms a delayed cutaneous reaction
can be searched for after an intradermal
injection of leishmanin (Fig. 749), namely an
extract of leishmania in phenol saline. When
interpreting this reaction, physicians should
take into account that in endemic areas after
childhood there are many sensitized subjects.
Leishmanias can also be grown from a scrap of
tissue inseminated in brain-heart medium with red
cells of rabbit (Fig. 751).
Although the cutaneous lesions spontaneously
heal, the time, which is necessary for healing,
cannot be predicted.
This is why cutaneous leishmaniasis is usually
treated with intralesional injection of antimony
Fig. 750: Typical
appearance of intraphagocytic Leishmania in the
a skin lesion.
Fig. 751: Flagellate form of
Leishmania in culture (Brain-heart with
defibrinated blood of rabbit)
When the nodule is small a
single intralesional injection is enough, whereas larger
lesions require more than one injection in order to
infiltrate all the lesions. Antimony salts at a dose of
20 mg/kg per day per intramuscular injection are not
devoid of side effects. This is why the systemic
treatment should be reserved to disseminated forms, which
are at risk for unaesthetic scars, and continued till the
healing of the lesions (usually 10-15 days).
Scabies. Scabies is an infestation due to a mite,
namely Sarcoptes scabiei. The variety hominis is
reponsible for human scabies and specific of the human
skin, namely it is able to reproduce itself only in the
human epidermis. There is a specific mite for every
mammalian, namely the mite of dog scabies, that one of
the cat scabies etc., which are able to reproduce
themselves only in the epidermis of the dog, cat etc..
These mites can sting the human. However, they cannot
reproduce themselves and thus persist in the human
epidermis. Therefore, once treated the cat or dog, the
lesions caused in the man by their specific mites
The female mite, after mating, excavates a burrow inside
the horny layer and here deposits her eggs. The latter
within a few days hatch and the emerging larvae get adult
and mate them selves, giving raise to a new cycle. The
infestation regresses only when all the adults and larvae
The mite of scabies survives for a very short time out of
the human skin. This is why the contagion is
interpersonal, following a close contact, usually
sleeping in the same bed. The contagion also depends on
the predisposition to be affected and the amount of
The predisposition does not depend on specific immunity,
which does not exist, probably because the mites stay
very superficially and do not come in contact with the
immunocompetent structures of the skin. On the other
hand, the predisposition is natural and different in the
various subjects. This partially explains the strange
resistance of some subjects of the same family group.
The amount of mites is also important, as shown by the
so-called Norwegian scabies, which is highly contagious
because the skin is plenty of burrows and then is teeming
with mites. The amount of mites is also important in
determining the incubation period of the disease, ranging
between a few days and several weeks. From an
epidemiological point of view, sex and age of the subject
are not important. With regard to the age, scabies may
occurs from the second week of life till death.
The itching is the most important symptom, which often
leads the patient to the doctor. The most important
characteristic of the scabies itching is that it is often
simultaneously present in many members of the family
group and that it arises in the various subjects of the
same family group with an interval of 2-3 weeks. In spite
of this rule, it is possible that only a subject remains
affected in a family group for a long time. This usually
occurs in the subjects, who have and use all the hygienic
We usually read that scabies itching prevails during the
night and deteriorates when going to bed. Really this is
the rule in all the most itching disorders and
particularly in atopic dermatitis.
The lesions of scabies have a characteristic morphology
and distribution. The initial and more characteristic
lesion is the burrow (Fig. 756), namely a linear lesion,
which is 4-12 mm long and less than 1 mm large. The
latter is due to the walking of the female mite inside
the horny layer with deposition of the eggs. On the other
hand, the pearly vesicle, which can be isolated or at the
end of a burrow, is found much more rarely. The vesicle
probably corresponds to the end of walking of the female
and can be more easily observed in the palmar region,
where it can persist longer thanks to the thicker horny
layer. The pearly vesicle should be differentiated from
the palmar and plantar pustules, which can be shown after
a treated scabies in the first year of life. The latter
are turbid and do not contain mites.
Besides burrows and pearly vesicles, which can be
considered the specific lesions of scabies, there are
other lesions in this disorders, such as papules and
vesicles of various size and scratch marks of various
Moreover, there are granulomas. The latter are 5-20 mm in
size, reddish or red-brownish, firm nodules. These
nodules, which are characteristic of children, often
arise some weeks after the onset of the disease and do
not contain mites. These nodules should probably be
considered as a foreign body reaction against exogenous
material, which penetrated inside the dermis by
scratching. Characteristically, the nodules periodically
get more inflamed, with transitory significant increase
of itching and size.
Finally, there are eczematous and impetiginized lesions,
which are expression of the complications due to
The presence of burrows, pearly vesicles, nodules,
eczematous and impetiginized lesions gives a
characteristic polymorphism to the clinical features of
Besides this polymorphism, the distribution of the
lesions immediately suggests the diagnosis of scabies.
The distribution of the lesions is so characteristic that
it should be mentioned in details as follows:
interdigital spaces of the hand, ulnar margin of the
hand, flexor aspect of the forearm, extensor aspect of
the elbow, anterior pillar of the armpit, genitalia,
subgluteal furrow and plantar surface in children. The
head is never affected, except for the first months of
life. Primary and secondary genitalia are even more often
affected in adolescents and adults. Physicians should
also remember that the ulnar aspect of the hand, which is
rarely involved in other skin disorders, has a high
diagnostic value. We do not know exactly the reason of a
so typical distribution, although somebody hypothesized
that are elective the sites that cannot be easily
Scabies should be differentiated from all the other itchy
skin disorders and particularly atopic dermatitis (AD).
The family history for itching can be positive in AD.
However, it is unlikely that two subjects of the same
group started to scratch with an interval of a few weeks
each other. The elective sites of AD are different, its
lesions are less polymorphous and there are not gross
nodules. When burrows are identified, the differential
diagnosis is easier. In the doubtful cases the research
of parasites in the lesions can be diriment.
The treatment is based on some basic principles, which
should be known and respected. They are more important
than the choice of the acaricide. Scabies does not give
immunity and then can relapse more times. This is why all
the subjects with suspected scabies belonging to the same
family group must be simultaneously treated. The
acaricide treatment must be repeated 5-7 days after the
first rubbing, to be sure of killing the mites deriving
from the eggs hatched after the first treatment. The
treatment should be performed on the entire skin surface,
except for the head, after a warm bath aimed at soaking
the more superficial layers of the skin and therefore
expose the parasites to the direct action of the
acaricide. The treatment itself is irritant and can cause
Practically, after a warm bath, the acaricide is rubbed
with a gauze on the entire skin surface, insisting on the
elective areas and the areas more affected by the
lesions. The rubbing should be repeated 2-4 times with an
interval of 12-36 hours. Under 1 year of age it is better
an interval between rubs larger than 24 hours. As
acaricide, 25% (15-20% under 1 year) benzyl benzoate in
petrolatum oil can be used (shake well before using) or
one of the other drugs actually on sale. We are waiting
for ivermectin, which is not yet on sale for human usage.
After treatment, nodules can persist for a long time,
even many months. Periodically, nodules undergo crises of
itching and inflammation. In this case topical
corticosteroids creams should be given. A specific
treatment is not necessary, unless numerous new lesions
appear on the entire skin surface.
Besides nodules, also palmar and plantar pustules can
persist for a long period of time in children aged less
than one year. Also these pustules do not contain mites
and do not need a specific treatment for scabies.