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Pityriasis rosea
(pityriasis = fine scales, rosea = rose or pink color) is a common
self-limiting rash that usually involves children and young adults. A
primary lesion is typically followed by a more generalized rash that appears
in crops. The disease may have many clinical variations. It has some
characteristics of a viral infection.
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ETIOLOGY & PATHOGENESIS |
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The cause of PR is
unknown but several features of the disease suggest a viral etiology:
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Seasonal variation, a
generalized rash following a primary patch, a limited course, rarity of
second attack and familial clustering of cases resemble features of a
viral exanthem. No infective agent, however, has been consistently
recovered from the patients.
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Pityriasis rosea-
like eruption may be caused by a number of drugs like,
bismuth, gold, metronidazole, captopril, penicillamine,
barbiturates, isotretinoin, levamisole, omeprazole, ketotifen, and
clonidine.
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CLINICAL FEATURES |
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PR can occur in any
age but it is commoner in the age group 10 to 35.
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Relatively more
common in females.
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There is no racial
preference.
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The typical rash
begins with a single lesion that heralds the onset of a more generalized
rash that comes after a variable period of time. The first lesion is known
as the herald patch (also called primary plaque of mother patch).
Pink of salmon colored, the herald patch is a well-marginated round or
oval papulosquamous lesion that enlarges to a diameter of about two to ten
cm. It has a collarette of scales attached to the periphery of the lesion.
The scales have a free margin internally. The centre of the lesion is
mildly atrophic and has a characteristic wrinkled appearance. The herald
patch usually appears on the trunk, proximal limbs or the neck.
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One to two weeks
after the appearance of the herald patch, the
secondary rash appears in
crops. Appearance of the secondary rash may rarely be delayed for 2 to 3
months or they may appear almost simultaneously. The lesions usually have
a central distribution, on the trunk and proximal limbs. The secondary
lesions are miniature forms of the herald patch with an average diameter
of 1 to 1.5 cm. The long axis of the oval lesions tends to remain parallel
to the cleavage lines. On the trunks they occur parallel to the ribs
giving rise to the characteristic ‘Christmas tree’ appearance.
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Crops of lesions may
appear during the next four to six weeks, following which the disease
remits spontaneously, usually without a trace, but may leave temporary
post-inflammatory hypo- or hyperpigmentation. PR is mildly symptomatic
with about three-fourth of the patients complaining of varying degrees of
itching.
Variants
and atypical forms:
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No herald patch.
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More than one herald
patch
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Herald patch may be
the only manifestation.
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Exclusively
peripheral distribution (inverse PR)
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Craniocephalic
distribution
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Unilateral
distribution
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Giant lesions
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Oral mucosal lesions:
erosions, ulcers, bullae
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Morphological
variants: papular and vesicular variety, purpuric and erythema
multiforme-like lesions.
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DIFFERENTIAL DIAGNOSIS |
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Secondary syphilis
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Guttate psoriasis
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Seborrhoeic
dermatitis
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Lichen planus
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Pityriasis
lichenoides
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Drug eruptions
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Ringworm
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Nummular eczema
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Erythema multiforme
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DIAGNOSIS |
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COURSE AND PROGNOSIS |
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PR has an excellent
prognosis without any significant morbidity.
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Most of the cases
resolve within three months without any sequela.
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Some patients are
bothered by post-inflammatory pigmentary change which also resolves with
time. Second attack of PR is extremely rare.
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TREATMENT |
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No treatment may be
necessary for mildly symptomatic or asymptomatic cases.
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For relief of
pruritus, antihistaminics may be prescribed along with application of
lotio calamine.
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Topical steroids are
often prescribed for relatively severe cases. A short course of systemic
steroids may rarely be necessary.
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Phototherapy with UVB
may also be used.
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