Spinal Muscular Atrophy with Two SMN2 Copies and Preserved Deep Tendon Reflexes: An Extremely Rare Case

Introduction and Aim: Spinal muscular atrophy (SMA) type 1 is the most severe form of SMA, in which deep tendon reflexes cannot be elicited. It accounts for 50-70% of cases of childhood onset SMA. Our search of the literature reveal no instances of SMA with preserved reflexes except for one case report1. The present report describes a child aged 35 months with SMA with two SMN2 copies with preserved deep tendon reflexes, an extremely atypical phenomenon. Material and Methods: We report this extremely rare case together with video images. The patient was diagnosed with SMA type 1 (two SMN2 copy numbers) as a result of SMN gene analysis. She had two siblings who died at six months of age. No hypoxia was present in her prenatal, natal, or postnatal histories. Intrathecal nusinersen therapy was initiated at the age of 1.5 months. The case was evaluated together with history and neurological examination findings. Results: The patient was able to walk independently, run, and climb stairs at physical examinations performed at 35 months of age. Her HFMSE score was 57. She was capable of using a fork and spoon and of forming three or four-word sentences. Bilateral deep tendon reflexes were evaluated as normoactive since she was 1.5 months years old (++/++ from the patella) (video images are available). Conclusion: This is an extremely interesting case in terms of the preserved deep tendon reflexes as well as a favorable course in the prognosis of motor functions.
Keywords: Spinal muscular atrophy, SMN2 copy number, deep tendon reflexes