Severe Combined Immunodeficiency with De Novo Duchenne Muscular Dystrophy Mutation.

Both severe combined immunodeficiency (SCID) syndrome and Duchenne muscular dystrophy (DMD) are rare conditions. Patients with X-linked SCID have pathogenic variants of the IL2RG gene, resulting in defective cellular and humoral immunity. DMD is also an X-linked condition caused by a dystrophin gene mutation, causing progressive proximal muscle weakness. We present a patient diagnosed with SCID at birth who underwent matched unrelated donor bone marrow transplant (BMT). Several months after, he was noted to have persistently elevated aminotransferases. Despite a lack of clinical signs of graft versus host disease (GvHD), a liver biopsy revealed mild GvHD. Creatine kinase (CK) levels of >19,000 U/L prompted evaluation for muscular dystrophies. Given BMT, genetic analysis was not an option. Muscle biopsy confirmed DMD. This case highlights the complexity of diagnosing and managing uncommon genetic conditions through a multidisciplinary team-based approach. This case is only the second reported case of SCID and DMD together.