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Pityriasis rosea; Pityriasis circinata; Pityriasis maculata

Etiology: 1) unknown, most likely caused by an infectious agent a) discrete clinical course b) apparent lifelong immunity after illness 2) increased incidence is associated with: a) atopy b) seborrheic dermatitis c) acne vulgaris d) dandruff Epidemiology: 1) moderately common 2) worldwide distribution 3) all races affected 4) peak incidences in spring & autumn in temperate zones 5) females affected slightly more than males 6) most patients are 10-43 years of age Pathology: * histopathology image [6] Clinical manifestations: 1) self-limited condition lasting 4-8 weeks (1-3 months [1]) 2) occasional mild 'viral syndrome-like' prodrome - recent upper respiratory tract infection [1] 3) mild pruritus 4) herald patch (primary lesion) a) single, round or oval (annular) erythematous to salmon-colored patch 2-6 cm in diameter with a peripheral rim of scale b) generally occurs on the trunk (Christmas tree pattern) c) precedes the macular papular lesions by 2-21 days 5) secondary lesions a) macules or papules involving the trunk, less frequently the extremities, scalp & face - skin color to pink - typically spares palms & soles [1] b) lesions are usually oval & follow the crease lines (Langer lines) of the skin c) 0.5-1.5 cm in diameter d) lesions appear in crops, adopts 'Christmas tree' pattern on trunk e) distribution mainly on torso, but may affect proximal extremities f) lesions may continue to appear for 2-3 weeks g) complete resolution of rash in 6-14 weeks 6) recurrences are uncommon (3%) 7) involvement of internal organs does not occur * images [5,6,7] Laboratory: 1) RPR in sexually active persons (rule out syphilis) [1] 2) histopathology on skin biopsy is non-specific Differential diagnosis: 1) secondary syphilis a) not pruritic b) history of prior genital lesions c) positive serology d) more common on palms & soles e) generalized lymphadenopathy common 2) tinea versicolor a) lesions are more brown b) borders are not as ovoid c) KOH testing usually positive for hyphae 3) drug eruptions a) generally no herald patch b) history of exposure to agents reported to cause rash resembling pityriasis rosea 1] bismuth 2] barbiturates 3] captopril 4] D-penicillamine 5] gold 6] isotretinoin 7] metronidazole 8] sulfa drugs c) resistant to therapy with protracted course d) larger lesions 4) psoriasis a) found predominantly on extremities & scalp b) rash has whiter, thicker scale c) more chronic course 5) seborrheic dermatitis a) chronic clinical course b) irregular, greasy scales c) hairy areas affected d) no herald patch 6) lichen planus a) more papular & violaceous b) involve mucosa of mouth & lips 7) Kaposi's sarcoma a) oval, violaceous plaques b) no scaling 8) nummular eczema a) generally not confined to the trunk b) round lesions c) more chronic course Management: 1) disorder is self-limited, so treatment is symptomatic 2) pharmacologic agents a) oral antihistamines for pruritus b) topical glucocorticoids c) systemic glucocorticoids for severe pruritus 1] oral prednisone taper a] begin 20-40 mg QD b] taper over 1-2 weeks 2] triamcinolone acetonide (Kenalog) 40 mg IM 3) UV-B phototherapy (sunlight) 5) patient education a) self-limited b) NOT contagious

General

pityriasis

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 15, 16, 17, 18. American College of Physicians, Philadelphia 2009, 2012, 2015, 2018. - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  2. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 800
  3. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 950-51
  4. Browning JC. An update on pityriasis rosea and other similar childhood exanthems. Curr Opin Pediatr. 2009 Aug;21(4):481-5. PMID: 19502983
  5. Pityriasis rosea (image) American Academy of Dermatology https://www.aad.org/public/diseases/rashes/pityriasis-rosea
  6. Schwartz RA, Elston DM (images) Medscape: Pityriasis Rosea http://emedicine.medscape.com/article/1107532-overview
  7. Pityriasis rosea. Pityriasis rosea. (images) http://www.dermnetnz.org/viral/pityriasis-rosea.html
  8. Wollenberg A, Eames T. Skin diseases following a Christmas tree pattern. Clin Dermatol. 2011 Mar-Apr;29(2):189-94 PMID: 21396559