Lupus Miliaris Disseminatus Faciei and Follicular Mucinosis: A New Pattern of Janus Kinase Inhibitor Acneiform Eruption.

We present the case of a 64-year-old patient with a previous history of atopic dermatitis and vitiligo, who presented to the dermatology clinic with persistent "bumps" on his face that appeared following treatment with upadacitinib. Examination of the skin revealed multiple skin-colored to erythematous folliculocentric papules located on the temples, lateral canthi, and eyelids. A punch biopsy demonstrated a folliculocentric process; a central follicle exhibited a robust necrotizing granulomatous infiltrate associated with hair follicle destruction. The base of the follicle displayed follicular mucinosis and a lymphocytic infiltrate with an increased CD4:CD8 ratio of 8:1, retention of CD2 and CD5, and diminished CD7 expression. Subsequent PCR analysis showed no evidence of monoclonal T-cell receptor gene rearrangement. Based on the clinical impression, the histopathological features, and ancillary test results, a diagnosis of lupus miliaris disseminatus faciei with follicular mucinosis in the context of Janus kinase (JAK) inhibitor therapy was established. Although acneiform eruptions ("JAK-ne") are known side effects of JAK inhibitor therapy, to the authors' knowledge, this novel case report is the first to describe patterns of lupus miliaris disseminatus faciei and follicular mucinosis within the spectrum of inflammatory papular facial eruptions associated with JAK inhibitor therapy.