Expanding the phenotype of RBCK1-associated polyglucosan body myopathy type 1

Polyglucosan body myopathy-1 (PGBM1) is an extremely rare glycogen storage diseases that leads to muscle weakness and cardiomyopathy due to the accumulation of polyglucosan bodies. The clinical presentation appears to be partially dependent on the genetic mutation, but no clear genotype/phenotype correlation is currently possible.We describe a 7 year old patient, who initially presented with recurrent vomiting and respiratory infections until her first year of life. Diagnostic workup revealed an achalasia and the whole exome sequencing revealed an homozygous RBCK1 (RANBP2-type and C3HC4-type zinc finger containing 1) variant (c.896_899delAGTG) located in exon 7 (mid-domain), which has also been described in 4 patients with PGBM1.The unusual presentation with gastrointestinal and respiratory symptoms before the development of progressive muscle weakness expands the phenotype of this disease.

Automated summary

Polyglucosan body myopathy-1 is a rare glycogen storage disease that causes muscle weakness and cardiomyopathy. The clinical presentation may be influenced by genetic mutations, but no clear genotype/phenotype correlation has been established. We report a 7-year-old patient who experienced recurrent vomiting and respiratory infections in her first year, and was subsequently diagnosed with achalasia. Whole exome sequencing revealed a previously described mutation found in other patients with this disease.