A case report of ADMIO type 1 caused by a de novo STAT3 gain-of-function mutation.

Infantile-onset Multisystem Autoimmune Disease type 1(ADMIO, 1) is a rare hereditary autoimmune disorder primarily caused by STAT3 gain-of-function (GOF) mutations. This article presents a case of ADMIO type 1 resulting from a de novo STAT3 GOF mutation. The subject is a male infant who presented with a recurrent rash on both lower limbs. He had a 9-month history of vasculitis, initially diagnosed as Henoch-Schönlein purpura(HSP), with recurrent purpura, ankle arthritis, livedo reticularis, and chronic diarrhea. Diagnosis was confirmed via whole-exome sequencing identifying a heterozygous STAT3 mutation (c.2107G>A, p.A703T). Symptoms recurred frequently during corticosteroid tapering. Due to his genetic findings, targeted therapy was required. Initial treatment with tocilizumab provided short-lived benefit. Following recurrent lymphadenitis and polyarthritis, adalimumab, tofacitinib, ruxolitinib emerged as a key anti-inflammatory intervention to treat the disease. This case enriches the rare disease database and helps raise clinicians' awareness of and attention to ADMIO type 1 disease.