A 44-year-old man presents with a red, mild-moderately pruritic rash on his chest with “islands of skin” that are spared from the rash. It started about two or three months prior to his visit. He also complains that the skin on his palms looks slightly orange and feels thicker.
Diagnosis: Pityriasis rubra pilaris
Upon initial clinical examination, I considered SCLE, psoriasis and also psoriasiform dermatitis (although some consider pityriasis rubra pilaris to be a type of psoriasiform dermatitis). The biopsy was consistent with Pityriasis rubra pilaris.
This condition is an inflammatory process in which lesions present themselves clinically as red macules and subtle scaly papules. They soon become so confluent that there is widespread redness and scaling punctuated by islands of skin that ostensibly are clear.
The first lesions of pityriasis rubra pilaris to present themselves are red macules that may become scaly patches, or papules that may become scaly plaques. The disease tends to become progressively widespread and, in time, an erythroderma may result. Characteristically, there are zones within the erythroderma of seeming unaffected (“islands of skin”). The scaling becomes ever more marked and is expressed most dramatically on the scalp. Palms and soles become hyperkeratotic and have a yellow-orange cast. In addition, ostia of follicles often are seen to be widened and plugged by horny material.
Pityriasis rubra pilaris usually lasts for months, sometimes years.
Integration: Unifying Concept
Pityriasis rubra pilaris is a distinctive inflammatory process whose morphologic features are unique, clinically and histopathologically. Papules of the condition are characterized by discrete foci of parakeratosis that alternate with orthokeratosis in both vertical and horizontal directions. The granular zone is prominent and the remainder of the epidermis is psoriasiform, rete ridges of the condition being shorter and broader than those of psoriasis. A thinly scattered profusion of lymphocytes appears around dilated venules of the superficial plexus. Tissue sections of the biopsy specimen of a horny plug within the ostium of a follicle show a dilated infundibulum filled with corneocytes that are both orthokeratotic and parakeratotic and arranged in a manner similar to that in the altered stratum corneum.
Topical corticosteroids are appropriate for localized scaly papules and plaques on the extremities, but PUVA or retinoids given systemically are necessary for treating widespread lesions. Extracorporeal photopheresis and cyclosporine also have been advocated for disease that is widespread.
For more information, contact Charles E. Crutchfield III, MD, at Crutchfield Dermatology or visit CrutchfieldDermatology.com.