BAG3 Myopathy Presenting With Prominent Neuropathic Phenotype and No Cardiac or Respiratory Involvement: A Case Report and Literature Review.

Bcl-2-associated athanogene 3 (BAG3) myopathy is a rare myofibrillar myopathy characterized by toe walking and clumsiness in the first decade with rapid progression to cardiomyopathy and restrictive lung disease in the second decade. Most patients (18 patients) have the c.626C >T (p.Pro209Leu) mutation. We describe BAG3 myopathy due to p.Pro209Leu in a 13-year-old girl with initial prominent neuropathic phenotype and no cardiac or respiratory involvement. Parents reported toe walking and clumsiness since 3 years old. Examination at the age of 13 years showed findings suggestive of Charcot-Marie-Tooth disease. Nerve conduction studies revealed demyelinating polyneuropathy. Next-generation sequencing panel for inherited neuropathies was unrevealing. Whole exome sequencing identified a de novo mutation in BAG3. Muscle biopsy confirmed myofibrillar myopathy. No cardiac involvement or symptoms of respiratory involvement at the age of 14 years. This case emphasizes the phenotypic variability of BAG3 myopathy and the importance of thorough electrophysiological examination and muscle pathology for establishing a precise diagnosis.