A 35-year-old man with severe psoriasis on secukinumab presented with a 3-week history of a gradually growing, painful, exophytic, infiltrated, and crusted nodule on the bridge of his left foot. No relevant history of trauma, fever, or other symptoms were reported.
Our differential diagnosis included squamous cell carcinoma, keratoacanthoma, mycobacterial infection, pyogenic granuloma, and viral wart. Curettage was performed with complete resolution.
Histopathology examination revealed the presence of lobular lesions of enlarged keratinocytes and eosinophilic amorphous bodies consistent with molluscum bodies (Henderson–Patterson bodies) surrounded by mixed inflammatory cells (Fig. 1). These findings were consistent with molluscum contagiosum (MC).
MC is a common benign condition caused by a double-stranded DNA poxvirus. MC often presents in children as a dome-shaped, skin-colored papule with a central umbilication. Although cases of atypical presentation have been reported in immunocompromised patients due to HIV, iatrogenic immunosuppression, or primary immunodeficiencies, few cases of MC in patients on biological therapy have been reported. This is the first case ever reported of a giant MC mimicking squamous cell carcinoma in a patient on anti-IL-17 biological therapy.
In cases of atypical presentation of MC, screening for an underlying immunosuppression state, and HIV is advised, since MC may be a marker of a weakened immune system.
