Early Presentation of Pityriasis Rubra Pilaris Mimicking Tinea Corporis: Diagnostic Challenges of a Rare Skin Condition.

BACKGROUND Pityriasis rubra pilaris (PRP) is a rare chronic inflammatory skin condition characterized by follicular, papulosquamous, reddish-orange scaling, palmoplantar keratoderma, and erythema with islands of sparing. Its heterogeneous clinical presentation makes the diagnosis of PRP quite challenging, especially at the initial presentation, as it can mimic common skin conditions. CASE REPORT We present a case with an early presentation of PRP in a 61-year-old Malay woman with underlying uncontrolled diabetes, and discuss evolving clinical course of her disease. She presented to a primary care clinic with a 3-week history of itchy, ring-like skin lesions that started on her neck and chest but subsequently spread widely on her chest, back, and upper extremities. She was first treated as having extensive tinea corporis but responded poorly to multiple courses of antifungal treatment. An initial skin biopsy that was taken at the dermatology clinic revealed features suggestive of erythema annulare centrifugum. However, despite topical steroid treatment, her skin condition evolved further and she developed generalized erythroderma along with follicular hyperkeratosis and palmoplantar keratoderma. A repeat biopsy finally confirmed the diagnosis of PRP. CONCLUSIONS Making the diagnosis of PRP is challenging for clinicians. However, clinicians should approach any common skin problem that does not respond to treatment appropriately, with consideration of other uncommon skin disorders. A repeat skin biopsy may be considered if there are any doubts about the diagnosis. A clinical and histopathological correlation is important to aid in the diagnosis of PRP.