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PITYRIASIS ROSEA

DERMATOLOGY LECTURE NOTES

DEBABRATA BANDYOPADHYAY
PROFESSOR & HEAD, DEPT. OF DERMATOLOGY,
R. G. KAR MEDICAL COLLEGE, CALCUTTA, INDIA

 

 

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.
 

 

ETIOLOGY & PATHOGENESIS

  • The cause of PR is unknown but several features of the disease suggest a viral etiology:

  • 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.

  • 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.

 

CLINICAL FEATURES

  • PR can occur in any age but it is commoner in the age group 10 to 35.

  • Relatively more common in females.

  • There is no racial preference.

  • 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.

  •  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.

  • 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:

  • No herald patch.

  • More than one herald patch

  • Herald patch may be the only manifestation.

  • Exclusively peripheral distribution (inverse PR)

  • Craniocephalic distribution

  • Unilateral distribution

  • Giant lesions

  • Oral mucosal lesions: erosions, ulcers, bullae

  • Morphological variants: papular and vesicular variety, purpuric and erythema multiforme-like lesions.

 

DIFFERENTIAL DIAGNOSIS

  • Secondary syphilis

  • Guttate psoriasis

  • Seborrhoeic dermatitis

  • Lichen planus

  • Pityriasis lichenoides

  • Drug eruptions

  • Ringworm

  • Nummular eczema

  • Erythema multiforme

 
 

DIAGNOSIS

 
 

 

 
 

COURSE AND PROGNOSIS

 
 
  • PR has an excellent prognosis without any significant morbidity.

  • Most of the cases resolve within three months without any sequela.

  • Some patients are bothered by post-inflammatory pigmentary change which also resolves with time. Second attack of PR is extremely rare.

 
 

TREATMENT

 
 
  • No treatment may be necessary for mildly symptomatic or asymptomatic cases.

  • For relief of pruritus, antihistaminics may be prescribed along with application of lotio calamine.

  • Topical steroids are often prescribed for relatively severe cases. A short course of systemic steroids may rarely be necessary.

  • Phototherapy with UVB may also be used.

 

 
 

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