CPC09 Trichodysplasia spinulosa masquerading as seborrhoeic dermatitis in a renal transplant recipient

Abstract

A 74-year-old man presented with a 4-month history of a mildly pruritic facial eruption, 1 year after a renal transplant for myelo­peroxidase-specific antineutrophil cytoplasmic antibody-associated vasculitis. He had previously received rituximab and cyclophosphamide, and post-transplantation maintenance immuno­suppression included mycophenolate mofetil and tacrolimus. The tacrolimus dose had been reduced by one-third 3 months prior to symptom onset. Initial management with multiple topical antifungals for suspected seborrhoeic dermatitis was ineffective, prompting referral to dermatology. Examination revealed numerous folliculocentric white filiform projections on the forehead, nose, cheeks and ears with diffuse scalp alopecia and near-complete loss of eyebrows and eyelashes. Differentials included lichen spinulosus and trichostasis spinulosa. However, this distinctive eruption of keratin spines in the context of solid organ transplant immunosuppression favoured a clinical diagnosis of trichodysplasia spinulosa (TS). A skin biopsy demonstrated abnormally maturing hair follicles, with excessive inner-root-sheath differentiation, exhibiting large trichohyalin granules and viral-like inclusions. SV40 immunostaining was positive, supporting polyomavirus-associated TS. Topical cidofovir was considered but not initiated due to limited availability and cost. Following multidisciplinary discussion, mycophenolate mofetil was stopped and a topical retinoid was introduced; oral valganciclovir was reserved as the next treatment option. The patient died following an exacerbation of interstitial lung disease before treatment response could be assessed. TS is a rare, likely under-reported cause of folliculocentric spicules in immunosuppressed patients, particularly solid organ transplant recipients. Identification of TS-associated polyomavirus from plucked spicules has implicated viral aetiology; however, the exact pathogenesis is unclear given high seroprevalence in the general population. There is no established therapy; reported approaches include reduction of immunosuppression, topical cidofovir 3% and oral valganciclovir. Notably, our patient developed TS following a reduction in immunosuppression with tacrolimus, further illustrating uncertainty around disease mechanisms. Early recognition in organ transplant recipients can prevent misdiagnosis and unnecessary antifungal treatment.