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Section 3 Psoriasis and Psoriasiform Dermatoses 65
Pityriasis Rosea ICD-9: 696.4 ° ICD-10: L42
■ Pityriasis rosea is an acute exanthematous
eruption with a distinctive morphology and often
with a characteristic self-limited course.
■ Initially, a single (primary, or “herald”) plaque lesion
develops, usually on the trunk; 1 or 2 weeks later
a generalized secondary eruption develops in a
typical distribution pattern.
Epidemiology and Etiology
Age of Onset. 10–43 years, but can occur rarely
in infants and old persons.
Season. Spring and fall.
Etiology. There is good evidence that pityriasis
rosea is associated with reactivation
of HHV-7 or HHV-6, two closely related
β-herpesviruses.
Clinical Manifestation
Skin Lesions. Herald Patch. Occurs in 80% of
patients, preceding exanthem. Oval, slightly
raised plaque or patch 2–5 cm, salmon-red, fine
collarette scale at periphery; may be multiple
(Fig. 3-20A).
exanthem. One to two weeks after herald
patch. Fine scaling papules and patches with
marginal collarette (Fig. 3-20B). Dull pink or
tawny. Oval, scattered, with characteristic
distribution following the lines of cleavage in
a “Christmas tree” pattern (Fig. 3-21). Lesions
usually confined to trunk and proximal aspects
of the arms and legs. Rarely on face.
Atypical Pityriasis Rosea. Lesions may be present
only on the face and neck. The primary plaque
may be absent, may be the sole manifestation
of the disease, or may be multiple. Most confusing
are the examples of pityriasis rosea with
vesicles or simulating erythema multiforme.
This usually results from irritation and sweating,
often as a consequence of inadequate
treatment (pityriasis rosea irritata).
■ The entire process remits spontaneously in
6 weeks.
■ Reactivation of human herpesvirus-7 (HHV-7) and
HHV-6 is the most probable cause.
Differential Diagnosis
Multiple Small Scaling Plaques. Drug eruptions
(e.g., captopril and barbiturates), secondary
syphilis (obtain serology), guttate psoriasis (no
marginal collarette), small plaque parapsoriasis,
erythema migrans with secondary lesions, erythema
multiforme, and tinea corporis.
Laboratory Examination
Dermatopathology. Patchy or diffuse parakeratosis,
absence of granular layer, slight acanthosis,
focal spongiosis, and microscopic
vesicles. Occasional dyskeratotic cells with an
eosinophilic homogeneous appearance. Edema
of dermis and perivascular infiltrate of mononuclear
cells.
Course
Spontaneous remission in 6–12 weeks or less.
Recurrences are uncommon.
Management
◧ ◐
Symptomatic. Oral antihistamines and/or topical
antipruritic lotions for relief of pruritus.
Topical glucocorticoids. May be improved by
UVB phototherapy or natural sunlight exposure
if treatment is begun in the first week of
eruption. Short course of systemic glucocorticoids.