A Case of Adult-Onset Still's Disease Caused by a Novel Splicing Mutation in Successfully Treated With Tocilizumab.

encodes the NF-κB regulatory protein A20. High-penetrance heterozygous mutations in cause a haploinsufficiency of A20 (HA20), inadequate inhibition of NF-κB pathway, and an early onset autoinflammatory disorder. However, the clinical phenotype of patients with HA20 varies greatly and clinical diagnoses prior to establishing the genetic cause, included both autoimmune and autoinflammatory conditions.