Myasthenia Gravis as a Manifestation of Aicardi-Goutières Syndrome Due to a SAMHD1 Variant Successfully Treated With Baricitinib.

Aicardi-Goutières syndrome (AGS) is a rare inherited disorder that mainly affects the brain, immune system, and skin. It is caused by mutations that lead to calcium buildup in the brain, which is thought to trigger an immune response. Autoimmune features, such as chilblains, overlap with those seen in systemic lupus erythematosus. We describe a case of a male toddler with an AGS phenotype and a heterozygous mutation in the SAMHD1 gene, who developed juvenile myasthenia gravis (MG) and was successfully treated with baricitinib. To our knowledge, this is the first reported case of AGS associated with MG. The patient showed significant clinical improvement, including resolution of myasthenic symptoms and normalization of autoimmune markers over an 18-month follow-up period. This case highlights the importance of considering broader autoimmune manifestations in AGS and the potential efficacy of Janus kinase (JAK) inhibitors such as baricitinib.