Page 190 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-15 Integumentary System

CLINICAL MANIFESTATIONS OF PUBIC LICE

LICE

Lice are nonflying insects that live off the blood meal
from a human host. They have been human pathogens Phthirus pubis
for thousands of years and continue to cause millions “crab louse”
of cases of disease annually. Three variants of the louse
exist: the head louse, the body louse, and the pubic Pediculosis
louse. For the most part, lice cause localized skin disease pubis (exposure
from the biting they do to secure their blood meal. of pediculi on hair)
However, some lice have been known to transmit other
diseases to humans. The most important infectious
agents transmitted by body lice are the bacteria that
cause epidemic typhus, relapsing fever, and trench
fever. These infections are uncommon in the United
States and North America but are still seen, and one
should be aware of their causes and vectors.
Clinical Findings: Lice are capable of infesting any
human, independent of age, sex, or race. Body lice are
seen more frequently in patients of low socioeconomic
status and especially in homeless individuals. Underly-
ing mental health issues in this subset may also predis-
pose one to conditions that are opportune for infestation. Maculae ceruleae. Faint, light
Pubic lice, or “crabs,” is a sexually transmitted disease blue macules on lower abdomen
that is seen in younger adults more frequently than in and upper thighs
other age groups; however, it has been reported to
occur in people all ages.
Pediculosis capitis (head lice infestation) is probably
the most common louse infestation in North America
and Europe. The louse, Pediculus humanus capitis, pref-
erentially locates to the scalp and lives between the hair
shafts. These lice are transmitted by close contact and
from fomites such as combs, pillows, and head rests.
Patients complain of severe itching on the scalp and
neck. On inspection, small (1-2 mm), red, excoriated
papules are seen. Evidence of scratching becomes
prominent as time goes on without a diagnosis. The
diagnosis is confirmed by finding a louse, which is typi-
cally 2 to 4 mm long and light brown in color. On
occasion, the abdomen of the louse can appear red,
which is the case directly after a blood meal. These
insects are not particularly fast moving, nor can they
fly or jump; as a result, they are easy to capture and
identify. Egg sacks (nits) are firmly adhered to the hair.
This is in contrast to the common hair cast, which can
easily be moved up and down the hair shaft with
minimal effort. The nits are laid in close proximity to
the scalp, usually within 0.5 mm. The nits hatch within
2 weeks. Therefore, nits found more than 2 cm from
the scalp are often nonviable, and the larva has already
emerged from the nit. Persistent infections can lead to
bacterial superinfection and pyoderma with cervical
adenopathy.
Pediculosis pubis (pubic lice infestation) is a com-
monly acquired sexually transmitted disease. The pubic eyelashes and eyebrows. This is important to look for inspection with the naked eye. Entomologists trained
louse, Phthirus pubis, is structurally different from the clinically, to appropriately treat all affected regions. in differentiating the species are capable of discerning
body or head louse and can easily be distinguished. Pediculosis corporis (body lice infestation) is com- the two. Body lice live on the clothing and leave it to
Patients complain of itching and often note pinpoint monly seen in homeless individuals and in those with feast on human blood. Patients present with multiple
drops of blood in their undergarments. This is caused poor hygiene. Historically, body lice have been associ- pruritic, red to pink, excoriated papules anywhere on
by small amounts of bleeding after the pubic lice feed. ated with epidemics during times of war, because close the body. On inspection of the skin, one typically will
These lice have specialized arms that allow them to contact for extended periods leads to easy transfer from not find lice. It is only with close inspection of the
climb around the entire human body, and they may be one host to another. The body louse, Pediculus humanus clothing or bedding material that the infestation
seen at any location. They have a tendency to affect the corporis, is indistinguishable from the head louse on becomes apparent. Hundreds to thousands of lice may

176 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS