Page 198 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-23 Integumentary System

Inflammatory
excoriated
papules
(note penile
involvement).
Involvement
SCABIES of genitalia,
umbilicus,
and finger
Human infection with the parasite Sarcoptes scabiei var webs is
hominis causes scabies. Humans are the only known characteristic
host, and the parasite is transferred from one person to Scabies (Sarcoptes for scabies.
another by close physical contact. scabiei in circle)
Clinical Findings: Scabies mites can affect any human.
Men and women are equally affected, and there is no
race predilection. The rash of scabies is highly pruritic.
Patients often scratch in front of the examining physi-
cian and cannot stop themselves from doing so. Patients
often state that it is the worst itching sensation they have
ever experienced. The itching sensation is worse in the
evening, especially when one is trying to sleep. Cutane-
ous findings are variable. Burrows are the hallmark of
scabies and are pathognomonic for the disease.
Burrows consist of a fine, 0.5- to 1.0-mm-wide, 0.5-
to 1.5-cm-long area of undulating or serpentine regions
with a tiny black speck at one end. This tiny black speck
is the scabies mite that is burrowing along the skin. If
one were to scrape the area of the burrow where the
mite is located and examine the scraping under the
microscope, a mite would surely be seen. The mite may
also be seen in association with eggs and scybala (mite
feces). Any of these findings confirms the diagnosis.
Burrows are most commonly appreciated along the
sides of the fingers and the wrists.
The palms are commonly affected with tiny (1 mm)
patches within the skin lines. They are intensely pru-
ritic and are associated with excoriations. Scabies mites
avoid the areas of the body that contain numerous seba- The face is
ceous glands and for this reason are almost never seen typically
on the face of anyone past the age of puberty. They may spared
be found on the face of infants and children, who have except in
not yet formed mature sebaceous glands. Scabies also neonates
has a propensity to affect the genitalia. The scrotum is and
almost always affected in cases that are more than a few immuno-
weeks old. Very few rashes cause papules or nodules on suppressed
the scrotum, and the presence of itchy nodules on the patients.
scrotum should be considered a sign of scabies until
proven otherwise.
Crusted or Norwegian scabies is a rare form of scabies
seen in immunosuppressed individuals. The crusted
lesions represent the actions of hundreds to thousands
of scabies mites. Patients are often covered from head
to toe and are extremely pruritic. A scraping shows the
presence of numerous mites. Individuals with crusted
scabies should be treated with a multimodal approach.
Scabies can cause outbreaks in long-term care facili-
ties. These outbreaks can affect many individuals within
the facility and are difficult to eradicate. Child with scabies, ventral view Child with scabies, dorsal view
Histology: Skin biopsies are rarely performed. If a
biopsy were to be done, one would see a mixed inflam-
matory infiltrate in the dermis with many eosinophils.
This is a nonspecific finding and can be the result of
any bug bite reaction. If the actual mite is biopsied, 3 days and releases a larva. The larvae quickly grow and any recently hatched mites are killed before they can
scabies parts will be present within the epidermis. form nymphs and then mature adult mites. This process reach reproductive age. Colloidal sulfur may be used on
Pathogenesis: S. scabiei is spread from one human to occurs within 1 week’s time. The mites have a life span pregnant women. It is efficacious and safe but has a
another by close physical contact. The mite burrows into of 2 months. The female mite can lay 3 eggs per day. terrible odor. Outbreaks in long-term care facilities are
the epidermis but is unable to penetrate the basement Treatment: Permethrin is currently the drug of often treated with oral ivermectin, which has shown
membrane zone. Its presence sets off a massive inflam- choice to treat scabies. It should be applied overnight good efficacy. Lindane has fallen out of favor because
matory response. The female mites lay eggs as they and repeated in 1 week, because it is pediculicidal but of its potential neurotoxicity. The use of malathion is
burrow through the skin. Each egg hatches within 2 to not ovacidal. The second application makes sure that advocated if permethrin fails.

184 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS