Hereditary Myopathy With Early Respiratory Failure Associated With an Incidental COL4A5 Variant: A Case Report

Background Hereditary myopathy with early respiratory failure (HMERF) is a rare autosomal dominant disorder caused by TTN variants. COL4A5 mutations are linked to X‐linked Alport syndrome. Case Presentation A 34‐year‐old male developed progressive lower limb weakness, gait disturbance, nocturnal hypoventilation, and calf hypertrophy. Family history revealed similar symptoms in his mother and sister. Examination showed absent reflexes; MRI demonstrated muscle atrophy and fatty replacement; needle electromyography (EMG) was performed and showed findings consistent with advanced myopathy; however, it was not used as a primary diagnostic tool. Whole‐exome sequencing identified a pathogenic TTN variant (c.95126C > G, p.Pro31709Arg), confirming HMERF. A hemizygous COL4A5 variant (c.4891C > T, p.Arg1631Cys) was also detected but lacked clinical correlation. Discussion and Conclusion This case illustrates a classic HMERF phenotype confirmed genetically, with an incidental COL4A5 variant of uncertain significance. It underscores the importance of genomic testing in atypical neuromuscular presentations and the need for cautious interpretation of incidental findings.