Intrafamilial phenotypic variability of DNAJB6 mutation associated autosomal dominantly inherited myopathy: a family report and literature review

Abstract

Objective To summarize the clinical phenotypes and genetic mutations of DNAJB6 related myopathies. Methods We retrospectively reviewed the clinical information, laboratory tests, muscle MRIs, electromyography results, muscle pathology examinations and genetic mutations of 2 patients of DNAJB6 related myopathies from one family and reviewed related published literatures of DNAJB6 related myopathies. Results The proband presented with muscle weakness of both proximal and distal limbs, with lower limbs more serious than upper limbs, and proximal more serious than distal. The father of proband presented with abnormal gait, and he could only climb stairs with assistance. Serum creatine kinase (CK) levels of both patients were normal. Muscle MRIs of both patients showed different degrees of fatty infiltration. Muscle biopsies of both patients showed similar changes with dystrophic features, and some muscle fibers with rimmed vacuoles inside, as well as increased internal nuclei and a few regenerating fibers. Genetic tests proved both patients carried the same DNAJB6 gene variant, c.161A ＞ C (p.Glu54Ala), which was the first report in mainland China. The proband was diagnosed as limb ⁃ girdle muscular dystrophy D1 (LGMD⁃D1) type, and the father of proband was diagnosed as distal myopathy. This family was considered as autosomal dominant DNAJB6 related myopathy. Referring to literature, heterogeneities exist in DNAJB6 related myopathies, and different clinical phenotypes could be presented in one single family. Conclusions The phenotypes of DNAJB6 related myopathies include limb ⁃ girdle muscular dystrophy and distal myopathy. Muscle pathology shows similar changes of rimmed vacuoles and dystrophic features. This reported family further expands the spectrum of phenotypes of DNAJB6 related myopathies. doi：10.3969/j.issn.1672⁃6731.2021.03.013

Keywords

• muscular diseases
• muscular dystrophies
• limb⁃girdle
• distal myopathies
• genes
• mutation
• pedigree