BAG3-Related Myofibrillar Myopathy Presenting as Hypercapnia:A Case Report and Literature Review

Objective BAG3-related myopathy is a rare condition so far reported in twenty patients worldwide.The purpose of this study was to draw attention to this rare disease and to the fact that BAG3-related myopathy should be considered as a rare differential diagnosis of hypercapnia.Methods We report a sporadic case of a 14-year-old Chinese girl with a de novo p.Pro209 Leu mutation in BAG3 and reviewed the literatures for reported cases related to this mutation.Results We described a 14-year-old Chinese girl who presented with gradually appearing symptoms of hypercapnia that required assisted ventilation.The muscle biopsy and the blood whole-exome sequencing results confirmed the diagnosis of myofibrillar myopathy with a de novo p.Pro209 Leu mutation in BAG3.Totally twentyone patients from twenty families with a confirmed diagnosis of BAG3-related myopathy were reported to date,including this patient and literature review.The male to female ratio was 11:10 and most showed initial symptoms in the first decade of life.Most patients presented toe/clumsy walking or running as the onset symptom,followed by muscle weakness or atrophy.Creatine kinase levels were elevated in fourteen patients and were normal in three.Eighteen patients developed respiratory insufficiency during the disease course and thirteen(one could not tolerate non-invasive assisted ventilation)required non-invasive assisted ventilation for treatment.Except for one not reported,heart involvement was found in seventeen patients during the disease course and seven underwent heart transplantation.Z-disk streaming and aggregation could be observed in most of the patients’muscle histology.In the long-term follow-up,five patients died of cardiac or respiratory failure.Conclusion BAG3-associated myopathy is a rare type of myofibrillar myopathy.It should be considered as a rare differential diagnosis of hypercapnia.

Identification of a novel nonsense mutation in kyphoscoliosis peptidase gene in an Iranian patient with myofibrillar myopathy

Myofibrillar myopathies(MFMs)are rare genetic and slowly progressive neuromuscular disorders.Several pathogenic mutations have been reported in MFM-related genes including DES,CRYAB,MYOT,LDB3 or ZASP,FLNC,BAG3,FHL1 and DNAJB6.Although MFMs is commonly inherited in an autosomal dominant manner,the inheritance pattern and novel mutated genes are not thoroughly elucidated in some cases.Here,we report discovery of a novel nonsense mutation in a 29-year-old Iranian male patient with motor disorders and deformity in his lower limbs.His parents are second cousins.Hereditary Motor Sensory Neuropathy as initial genetic diagnosis was ruled out.Whole exome sequencing using NGS on Illumina Hi-Seq4000 platform was performed to identify the disease and possible mutated gene(s).Our data analysis identified a homozygous nonsense unreported c.C415T(p.R139X)variant on kyphoscoliosis peptidase(KY)gene(NM_178554:exon4).Sanger sequencing of this mutation has been performed for his other related family members.Sequencing and segregation analysis was confirmed the NGS results and autosomal recessive inheritance pattern of the disease.