Severe atypical juvenile pityriasis rubra pilaris diagnosed in adulthood with a dramatic improvement with ustekinumab.

Pityriasis rubra pilaris (PRP) is a rare skin disease which manifests as a psoriasiform dermatosis and palmoplantar keratoderma and has significant clinical-histopathological overlap with psoriasis. Recently, several case reports have demonstrated successful treatment of PRP with anti-IL7A and anti-IL12/anti-IL23 monoclonal antibodies. We report a case of atypical juvenile PRP definitively diagnosed during adulthood with presence of CARD14 mutation. This case demonstrates a dramatic improvement with ustekinumab and highlights the role of genetic testing in chronic disease of diagnostic uncertainty.