Circumscribed juvenile-onset pityriasis rubra pilaris with hypoparathyroidism and brachyonychia.

Circumscribed juvenile-onset pityriasis rubra pilaris (PRP) manifests as well-defined erythematous scaly plaques with follicular keratosis mainly over the elbows and knees. There are several reports of the association of PRP with other conditions. We report a boy with scattered erythematosquamous skin lesions and follicular hyperkeratotic papules since he was 6 years old. Results of a skin biopsy were compatible with PRP. The patient also had hypoparathyroidism and brachyonychia. To our knowledge, this association has not been reported to date, though minor disturbances of calcium and vitamin D metabolism have been mentioned in some disorders of keratinization. We further discuss the epidemiologic, clinical, and pathologic features of PRP; review the conditions associated with brachyonychia; and give a brief discussion about the possible role of calcium metabolism in disorders of keratinization.