Multisystem Complications in Spinal Muscular Atrophy Type III: Chronic Respiratory Failure and Intractable Epilepsy.

Spinal muscular atrophy (SMA) is a rare neuromuscular disorder characterized by progressive motor weakness with multisystem involvement. Type III SMA, also known as Kugelberg-Welander disease, typically presents in childhood and allows survival into adolescence and adulthood, during which cumulative complications may emerge. We report the case of a 19-year-old female patient with genetically confirmed SMA type III (zero copies of SMN1, two copies of SMN2) whose disease course was complicated by chronic respiratory failure with hypercapnia requiring non-invasive ventilation and intractable generalized epilepsy. She was born prematurely at seven and a half months via emergent cesarean section for placenta previa and maternal hemorrhage, requiring a one-month neonatal intensive care unit stay with supplemental oxygen. SMA was diagnosed at 28 months of age following early motor weakness. Over childhood, she developed choking with thin liquids, weak cough during viral illnesses, and recurrent respiratory infections, with progression to restrictive lung disease and impaired airway clearance. At age 11, she developed head-drop seizures and was diagnosed with intractable generalized idiopathic epilepsy. Orthopedic complications included neuromuscular scoliosis requiring spinal fusion. This case underscores how SMA type III evolves into a multisystem disorder with cumulative respiratory, neurologic, and orthopedic morbidity, highlighting the need for vigilant longitudinal surveillance, proactive respiratory support, individualized seizure management, and coordinated interdisciplinary care.