Pemphigus Erythematosus Treated with JAK1 Inhibitor Upadacitinib: A Case Report and Brief Literature Review.

Pemphigus erythematosus (PE) is a rare subtype of pemphigus, and management may be particularly challenging when prolonged systemic corticosteroid exposure is undesirable. We report a 31-year-old woman with PE and concomitant erosive gastritis who received off-label treatment with the selective Janus kinase 1 (JAK1) inhibitor upadacitinib after continued systemic corticosteroid therapy was considered unsuitable. Despite initial treatment with methylprednisolone plus upadacitinib 15 mg daily, the disease progressed rapidly, prompting escalation of upadacitinib to 30 mg daily. New blister formation ceased within 1 week, methylprednisolone was discontinued by week 4, complete clinical resolution was achieved by week 8, and anti-desmoglein 1 antibody levels normalized by week 11. After disease control had been achieved, upadacitinib was reduced to 15 mg daily and discontinued after 8 months, with sustained remission and no treatment-related adverse events during 1 year of follow-up. In the context of limited published experience with JAK inhibitors in pemphigus, this single case provides preliminary evidence that upadacitinib may warrant further investigation as a potential corticosteroid-sparing option for selected patients with PE and treatment-limiting comorbidities.