Christmas tree appearance in skin is seen in -

Ans. is 'a' i.e., Pityriasis rosea Pityriasis rosaceao P. rosea is a common scaly disorder, occuring usually in children and young adults (10-35 years).o Characterized by round/oval pink brown patches with a superficial, centrifugal scale, distributed over trunk in a Christmas tree pattern.o The disease is thought to be viral disease, is self limiting, and subsides in 6-12 weeks.o The exact etiology is not known, but it is considered to be a viral disease; Human Herpes virus 6 (HHV 6) and Human Herpes virus 7 (HHV 7) may play a role.Clinical manifestations of P. roseao The disease starts with an upper respiratory prodrome or a mild flu.o After 1-2 weeks, Annular erythmatous plaque appears on trunk that is referred to as mother patch or herald patch.o Over the next 1-2 weeks, fresh patch appear all over the trunk, in a Christmas tree configuration or Fir tree Configration.o The lesions are pinkish in white skin, hence the name rosea.o However, on the dark Indian skin the lesions are skin coloured or brown.o The most characteristic clue for the diagnosis is the presence of a fine scale at the edge of the lesion referrred to as centrifugal scale or collarette scales or cigarette paper scales.o Lesions subside with hyperpigmentation.o Trunk is involved predominantly, Sometimes (in 20% of patients) lesions occur predominantly on extremities and neck (inverse pattern).