A case of widespread molluscum contagiosum caused by baricitinib, a Janus kinase inhibitor

Abstract

PEODDN is a congenital hamartoma, adult-onset cases have been described. 1 Histopathological examination shows an epidermal invagination with a parakeratotic column placed over a hyperplastic eccrine duct with a dilated acrosyringium and loss of the granular layer. 1 The exact pathogenesis of PEODDN is unclear. Positive immunohistochemical staining for carcinoembryonic antigen along the eccrine duct lumina and acrosyringium through the parakeratotic column of the cornoid lamellae leads to a suggestion that PEODDN result from circumscribed keratinisation abnormality relating to the hypertrophic and abnormal acrosyringia. 2 Moreover, mosaic mutation in GJB2 in these patients was indicated and introduced PEODDN as a possible mosaic form of KID syndrome. 4 Our case presented with late-onset asymptomatic linear keratotic papules, with sparing the face, palms and soles, but with characteristic histopathological features of PEODDN, which progressed despite various local and systemic therapies. 3 Various therapeutic modalities including cryotherapy, topical steroids, retinoids, 5-fluorouracil, anthralin, phototherapy 2 and oral retinoids 5 have been tried with limited efficacy. Although PEODDN is a benign disease, long-term follow-up are recommended because of possible progression to SCC or Bowen disease. 2

Cutaneous eruption after commencing baricitinib for rheumatoid arthritis

“…These reactions have included palmoplantar pustulosis 3 and widespread molluscum. 4 The precise mechanisms underlying inflammatory skin reactions in response to JAK inhibition are not completely understood. It is hypothesised that the interference with JAK-mediated signalling may disrupt the delicate balance between proinflammatory and anti-inflammatory cytokines, subsequently driving an overactive immune response within the skin.…”

“…Dermatological reactions to baricitinib have been infrequently reported in the medical literature. These reactions have included palmoplantar pustulosis 3 and widespread molluscum 4 . The precise mechanisms underlying inflammatory skin reactions in response to JAK inhibition are not completely understood.…”