Early onset respiratory failure in two pairs of unrelated Japanese siblings with SELENON-related myopathy

Background

SELENON-related myopathy is an autosomal recessive muscle disorder caused by SELENON variants and is clinically characterized by prominent axial muscle weakness, scoliosis, and severe respiratory dysfunction.

Case presentation

We present two pairs of Japanese siblings with SELENON-related myopathies. In all our cases, the initial symptoms were noted before the age of one year. All patients developed motor developmental delay and one of four individuals demonstrated poor weight gain. They started using noninvasive positive pressure ventilation between 5 and 9 years of age, and at least three of them did not complain of any symptoms until respiratory assessment. One patient presented with scoliosis and became wheelchair-bound at 11 years of age. Muscle pathology revealed nonspecific myopathic findings in all patients. They demonstrated a homozygous missense variant, c.1574T>G (p.Met525Arg), in SELENON.

Conclusion

In SELENON-related myopathy, respiratory function should be regularly examined, and noninvasive mechanical ventilation can be appropriately introduced. Therefore, we recommend the early diagnosis of SELENON-related myopathy.