Dr Neha Bansal

Definition : It is a common acute exanthematous skin disorder with unknown etiology. (1)

Age groups affected : Mostly occurs in children and young adults peaking at 20-29 years of age. (1) The male to female ratio is 1:1.43 (2)

Etiology : Due to its similarity to the various viral exanthemas, an infective viral etiology has been assumed due to the fact that outbreaks occur in clusters, presence of a prodromal phase and suggestions of long lasting immunity to the infection. (1,3) However, there is no evidence to linking it to any particular etiological agent. There have been various controversial reports of association with HHV-6 and HHV-7. (1,2) An allergic etiology has also been contemplated in the past. (3)

Signs & Symptoms : An upper respiratory tract infection precedes all symptoms. Then, a 2-10 cm herald patch, salmon pink colored with a collarette scale at the margin appears typically on the abdomen. (1) Secondary eruptions begin typically along the Langer (cleavage) lines after a few days to weeks which are similar to the herald patch and align in a "Christmas tree" appearance on the torso. (1,2) Patients, especially children, often experience mild to severe pruritis. (4)

Other associated symptoms like low-grade fever, nausea and headache are possible.

Atypical presentations have also been reported where the herald patch is either missing or confluent with other lesions.

Diagnosis : Biopsy usually shows non-specific signs of inflammation and is unnecessary. However, VDRL must be done to rule out secondary syphilis in case the patient is sexually active.

Treatment : It is most often self resolving in 5-8 weeks and no treatment is required. (1,2) Symptomatic treatments like antihistaminic, local calamine lotion and topical steroids have been used to decrease the itching. (1) Erythromycin and other macrolides have been used for treating pityriasis rosea. However the efficiency is still controversial. (1,2,4) Acyclovir has recently been added to the line of treatment after associations with HHV- 6, 7. (2,4) Phototherapy with UV radiation has shown to reduce the duration of the rash and intensity of itching though some studies show conflicting results. (1,2,4)

References :

	1.	Stulberg DL, Wolfrey J. Pityriasis Rosea. Am Fam Physician 2004; 69: 87-94
	2.	Chuh A, Lee A, Zawar V, Sciallis G, Kempf W. Pityriasis rosea - An update. Indian J Dermatol Venereol Leprol. 2005; 71: 311-315
	3.	Abercrombie GF. PITYRIASIS ROSEA 1964/65. J R Coll Gen Pract. 1968; 16: 268-274
	4.	Drago F, Rebora A. Treatments for pityriasis rosea. Skin Therapy Lett. 2009; 14: 6-7.