Eczema Molluscatum in a Patient With Atopic Dermatitis on Upadacitinib and Methotrexate.

Eczema molluscatum refers to widespread molluscum contagiosum (MC) infection occurring in patients with atopic dermatitis (AD), a setting in which impaired skin barrier function and immune dysregulation both promote viral spread. We report the case of a 29-year-old man with longstanding, treatment-refractory AD who was well controlled on upadacitinib, a selective Janus kinase 1 (JAK1) inhibitor, and methotrexate when he developed multiple pink, dome-shaped papules with central umbilication across the cheeks and forehead over a six-month period. The lesions were unresponsive to topical clindamycin-benzoyl peroxide gel. The differential diagnosis included eczema coxsackium, eczema herpeticum, eruptive syringomas, and a refractory JAK inhibitor-associated acneiform eruption, but the absence of pain, systemic symptoms, vesiculation, and follicular morphology supported a diagnosis of eczema molluscatum. The patient was treated with cryotherapy for each lesion, with marked improvement at one-month follow-up. AD itself is a recognized risk factor for MC, reflecting the disease's inherent Th2-skewed, barrier-disrupted immune environment. However, this case raises the possibility that systemic immunosuppression with JAK1 inhibitors, particularly in combination with methotrexate, may further impair type I interferon-mediated antiviral defense and compound susceptibility to MC in patients with AD. Nonetheless, clinicians should maintain a high index of suspicion for eczema molluscatum in patients with AD on JAK inhibitor therapy who develop new facial papules, as these lesions are readily mistaken for a JAK inhibitor-associated acneiform eruption, potentially delaying appropriate treatment.