History: Pityriasis rubra pilaris is a chronic papulosquamous disorder of unknown etiology characterized by reddish orange scaly plaques, palmoplantar keratoderma, and keratotic follicular papules.   It was first described  by Tarral in 1828.  The disease may progress to erythroderma with distinct areas of uninvolved skin, the so-called islands of sparing.  The familial form of PRP typically begins in early childhood and has an autosomal dominant inheritance pattern.  The acquired form of PRP has a bimodal age distribution, with peaks in the first and fifth decades of life, but it can begin at any age.