Galactose treatment of a PGM1 patient presenting with restrictive cardiomyopathy

We report a patient diagnosed with PGM1‐CDG at 11 years of age after two biallelic likely pathogenic variants in PGM1 were found on research genomic sequencing. To our knowledge, he is the first patient with PGM1‐CDG to be reported with a restrictive cardiomyopathy. Other clinical manifestations included cleft palate, asymptomatic elevated transaminases, intellectual disability and myopathy resulting in exercise intolerance. He was trialed on oral galactose therapy in increasing doses for 18 weeks to assess if there was any biochemical and clinical benefit. His galactose was continued for a further 9 months beyond the initial galactose treatment period due to improvements in exercise tolerance and myopathy. Treatment with galactose demonstrated an improvement in liver function and myopathy with improved exercise tolerance. Treatment with galactose for 15 months did not change heart function and exercise stress test results were stable.