P023 Acquired reactive perforating collagenosis in the setting of newly diagnosed primary biliary cholangitis

Abstract

Acquired reactive perforating collagenosis (ARPC) is a rare perforating dermatosis characterized by transepidermal elimination of altered collagen. It most commonly occurs in adults with diabetes mellitus or renal disease. Chronic pruritus and koebnerization are key pathogenic drivers. While metabolic associations predominate, ARPC arising secondary to cholestatic pruritus from liver disease is rarely reported. This case highlights the skin as an early marker of evolving systemic pathology. A 77-year-old woman with poorly controlled diabetes mellitus type II presented with a new, intensely pruritic papular eruption in parallel with evolving cholestatic liver dysfunction. Initial investigations were nondiagnostic. She re-presented weeks later with worsening cholestatic pruritus, painless jaundice and ascites, prompting further evaluation and liver biopsy, which confirmed primary biliary cholangitis (PBC). Despite high-potency topical corticosteroids with occlusion and topical antibiotic–steroid therapy, the cutaneous eruption progressed. Dermatological examination revealed widespread erythematous umbilicated papules with central keratotic plugs affecting the trunk and extensor surfaces. Given the perforating morphology in the context of systemic pruritus, a targeted skin biopsy was performed. Histology demonstrated a cup-shaped epidermal invagination containing vertically oriented degenerated collagen fibres with mixed inflammatory infiltrate, supporting a diagnosis of ARPC. Narrowband ultraviolet B (TL-01) phototherapy was commenced (19 sessions; cumulative dose 4920 mJ cm−2), resulting in a marked reduction in pruritus and near-complete clearance of lesions at the 3-month follow-up, despite a brief interruption for hepatic decompensation. This case illustrates that cholestatic pruritus from newly diagnosed PBC can trigger ARPC through koebnerization in a predisposed patient, underscoring the importance of recognizing perforating dermatoses as cutaneous markers of systemic disease. Early dermatological assessment and skin biopsy were pivotal in diagnosis, while TL-01 phototherapy provided effective steroid-sparing disease control.