Recessive RYR1-related centronuclear myopathy with congenital chylothorax in a Japanese male child

Introduction: The severity of RYR1 -related centronuclear myopathy (CNM) is typically intermediate between the most severe X-linked myotubular myopathy and mildly severe DNM2 -related centronuclear myopathy. We report a Japanese male patient with recessive RYR1 -related CNM that was exceedingly severe compared to previously reported cases and had congenital chylothorax, which is a very rare complication of congenital myopathy. Patient concerns: A male neonate from non-consanguineous Japanese parents presented with generalized hypotonia and respiratory distress at birth. Diagnosis: Muscle biopsy of the vastus lateralis showed typical features of CNM. The next-generation sequencing assay detected RYR1 gene mutations, which were c.5989G>A (p.E1997K) and c.1441-2A>G. These findings confirmed the diagnosis of recessive RYR1 -related CNM. Chest radiography showed bilateral pleural effusions at birth, which was diagnosed as chylothorax on laboratory examination. Interventions: Mechanical ventilation and tube feeding were initiated. Chylothorax was managed with drainage and treatment with octreotide acetate. Outcomes: His clinical course was so rapidly progressive that he could not move his fingers even when he was one year of age. Conclusion: Congenital chylothorax with congenital myopathy can be considered an indicator of a severe phenotype, and its presence may indicate poor prognosis.