The First Case of an Infant with Familial A20 Haploinsufficiency in Korea.

Haploinsufficiency of A20 (HA20) is a newly described autoinflammatory disease caused by loss-of-function mutations in the gene. Clinical phenotypes are heterogenous and resemble Behçet's disease, juvenile idiopathic arthritis, inflammatory bowel disease, or periodic fever syndrome, with symptoms developing at an early age. Here, we report the first case of infantile familial HA20 in Korea, which mimics neonatal lupus erythematosus (NLE). A 2-month-old infant exhibited symptoms including recurrent fever, erythematous rashes, and oral ulcers, with elevated liver enzymes, and tested positive for several autoantibodies, similar to systemic lupus erythematosus (SLE); therefore, she was suspected to have NLE. However, six months after birth, symptoms and autoantibodies persisted. Then, we considered the possibility of other diseases that could cause early onset rashes and abnormal autoantibodies, including autoinflammatory syndrome, monogenic SLE, or complement deficiency, all of which are rare. The detailed family history revealed that her father had recurrent symptoms, including oral and genital ulcers, knee arthralgia, abdominal pain, and diarrhea. These Behcet-like symptoms last for many years since he was a teenager, and he takes medications irregularly only when those are severe, but doesn't want the full-scale treatment. Whole-exome sequencing was conducted to identify a possible genetic disorder, which manifested as pathogenic variant nonsense mutation in the gene, leading to HA20. In conclusion, HA20 should be considered in the differential diagnosis of an infant with an early-onset dominantly inherited inflammatory disease that presents with recurrent oral and genital ulcerations and fluctuating autoantibodies. Additionally, it also should be considered in an infant with suspected NLE, whose symptoms and abnormal autoantibodies persist.