Case
of
the
Month
with
Crutchfield Dermatology
++++++++++++++++++++
+++ +
+++ +
++++++++++++++++++++
DIAGNOSTICS
Presentation: 12-year-old boy with itchy
bumps after swimming at lake cabin
What is your diagnosis?
Diagnosis: Swimmer's Itch
Swimmer's itch, also known as cercarial der-
matitis, is a distinctive papular eruption caused by
penetration of the skin by the cercariae of nonhuman
schistosomes. This cutaneous schistosomiasis is
usually limited to the exposed areas of the body. It is
commonly associated with fresh water lakes, although
a related condition known as "clam digger's itch" has
also been reported from the salt-water tributaries in
the Long Island Sound area of New York.
The cercariae responsible infect birds, rodents
or undulates, and belong commonly to the
species Schistosoma.
Cercarial dermatitis is a potential hazard worldwide
wherever people share an aquatic environment with
vertebrates and mollusks harboring schistosomes.
These blood flukes require an intermediate snail
host and a definitive vertebrate host to complete
their life cycle.
Inasmuch as humans are an accidental host,
complete development cannot proceed and clinical
manifestations of cercarial penetration resolve
spontaneously within a week. A prickling sensa-
tion lasting minutes to an hour after exposure
results from exposure to the schistosome-infested
waters. Pruritic erythematous macules, papules,
and occasionally papulovesicles and wheals can
be seen soon thereafter.
Repeated exposures can also produce a more
severe reaction. Postinf la mmator y hy per-
pigmentation is a common sequela. Edema,
lymphangitis and regional adenopathy develop
in some individuals, as may eosinophilia and
systemic symptoms of generalized urticaria,
nausea and vomiting. Once again, repeated
exposures produce more severe insect bite reac-
tions, with perivascular lymphocytes with more
severe bite reactions.
Treatment is oriented toward the relief of
symptoms. Oral antihistamines, topical steroids
and topical antipruritic agents may be helpful. The
rash may be prevented by toweling off vigorously
and showering promptly after freshwater bathing.
For more infor mat ion, contact Charles E.
Crutchfield III, MD at Crutchfield Dermatology or
visit www.crutchfielddermatology.com. ■
