KY (kyphoscoliosis peptidase) is a transglutaminase-like protease located on chromosome 3 that functions as a cytoskeleton-associated protein essential for skeletal muscle development and neuromuscular junction integrity 1. The protein is primarily involved in the formation and stabilization of neuromuscular junctions, likely through proteolytic cleavage of muscle-specific structural proteins such as filamin C (FLNC), supporting normal muscle growth and maturation 1. KY localizes to the Z disc and cytoplasm, positioning it to regulate sarcomeric architecture during muscle development 1. Loss-of-function mutations in KY cause myofibrillar myopathy-7 (MFM-7), an early-onset autosomal recessive muscle disorder characterized by progressive muscle weakness, muscle atrophy, joint contractures, and hyporeflexia 1. KY deficiency also contributes to hereditary spastic paraplegia (HSP), indicating broader roles in neuromuscular function 1. The identification of both frameshift and missense mutations in KY associated with MFM-7 underscores the critical importance of this protease's catalytic function in maintaining muscle architecture and neuromuscular transmission throughout life.