Sudden cardiac arrest in a child with nemaline myopathy

Background: Nemaline myopathy is a rare, non progressive congenital skeletal muscle disorder defined by the presence of inclusions known as nemaline rods in muscle fibers. Several clinical subtypes have been described, according to degree of muscle weakness, severity and age at onset. The course of nemaline myopathy is very slowly progressive, and death is usually due to respiratory failure. Cardiac involvement is rare and generally considered to be the result of ACTA1 mutations. Patient: We report the case of a 6 year old boy with typical congenital nemaline myopathy. Nemaline myopathy was confirmed at 3 years of age by muscle biopsy. No mutation of ACTA1, TPM2 and TNNT1 genes was detected. The child died suddenly of cardiac arrest and associated hypoxic-ischemic brain injury, in absence of acute respiratory failure or swallowing difficulties. Results: Nemaline cardiomyopathy was suspected, but post mortem cardiac biopsy did not show findings consistent with nemaline myopathy. Conclusions: Congenital typical nemaline myopathy is not necessarily a static or very slowly progressive disorder and acute cardiac deterioration can lead to early death.