ECEL1 (endothelin converting enzyme-like 1) is a type II membrane-bound zinc metalloprotease located on chromosome 2-q37 that plays a critical role in nervous system development and function 1. The protein degrades peptide hormones and neuronal peptides, functioning as a metalloendopeptidase similar to neprilysin and endothelin-converting enzyme 2. ECEL1 is predominantly expressed in neuronal cells and demonstrates significant transcriptional response to neuronal insults from the embryonic stage onward 2. Mechanistically, ECEL1 is essential for proper axonal arborization of motor nerves during development. Mouse studies show that DINE-deficient mice (the rodent homologue) exhibit impaired motor axon arborization in skeletal muscles, particularly affecting distal muscles, with reduced neuromuscular junction formation 3. The protein is also involved in nerve regeneration and central nervous system regeneration in mature animals 2. Autosomal recessive mutations in ECEL1 cause distal arthrogryposis type 5D (DA5D), a congenital disorder characterized by nonprogressive contractures affecting distal joints of the hands and feet, with additional features including ptosis, micrognathia, and scoliosis 456. Pathogenic mutations impair zinc ion binding or disrupt protein structure, compromising motor nerve development 7. DA5D shows a prevalence of <1/1,000,000 with myopathic features and innervation abnormalities observed on muscle pathology 4.