Case Report: A case of haploinsufficiency of A20 in a newborn with abnormal liver enzymes at disease onset.

A20 haploinsufficiency (HA20) is an early-onset monogenic autoinflammatory disease caused by loss-of-function variants in the TNFAIP3 gene, which encodes the A20 protein. Clinically, HA20 typically manifests with Behçet's disease-like features and often occurs in patients with a family history. Herein, we report a 1-month-old Chinese male infant who developed oral ulcers during the neonatal period, followed by recurrent fever, rash, elevated inflammatory markers, elevated liver enzymes, and positive lupus-related antibodies, with no relevant family history. Subsequent whole-exome sequencing identified a heterozygous variant in TNFAIP3: c.1876_1877del (p. Leu626ValfsTer45), leading to the diagnosis of HA20. The patient's symptoms resolved completely with glucocorticoid monotherapy. We recommend that HA20 should be considered in the differential diagnosis of autoinflammatory disorders in infants and young children presenting with recurrent fever and rash, even in the absence of a family history of HA20.