A novel de novo mutation in MYH7 gene in a patient with early onset muscular weakness and severe kyphoscoliosis: A case report.

Introduction: Various phenotypes have been identified for MYH7 gene mutation-related myopathy. Here, we describe a patient with severe muscular weakness and skeletal deformity with de novo heterozygous MYH7 gene mutation.

Patient Concerns: A 33-year-old woman presented with early onset of muscular weakness, with delayed motor development during infancy. At age 8 years, she was unable to walk, with signs of skeletal deformity, including the progression of kyphoscoliosis. At age 31 years, she developed dyspnea.

Diagnosis: She diagnosed with esophageal hiatal hernia with abdominal CT. In electromyography, short duration, small amplitude motor unit action potential (MUAP), and early recruitment patterns were observed in the involved proximal muscles, suggesting myopathy. Muscle histopathology showed fiber-type disproportion.

Interventions: Next-generation sequencing study revealed a heterozygous in-frame deletion variation in the exon 14 of the MYH7 gene (c.1498_1500del/p.Glu500del), which is a novel variation confirmed by conventional Sanger sequencing. Compared with the parental test, this variant was concluded as de novo.

Outcomes: She received laparoscopic hiatal hernia repair and Nissen fundoplication for esophageal hiatal hernia. After surgery, her postural dyspnea improved. As there is no fundamental treatment for MYH7-related myopathies, she continued conservative treatment for her symptoms.

Conclusion: Here, we presented a rare case of de novo mutation of the myosin head domain in the MYH7 gene. This report broadens both the phenotypic and genotypic spectra of MYH7-related myopathies.