The Institute of Myology jointly discovers a new form of X-linked distal myopathy

An international collaboration that included researchers from the Institute of Myology has discovered a new form of distal myopathy, in 10 men:

• with adult onset (over 30 years of age to 40 years), the muscle condition is distal and progresses slowly (ability to walk is maintained). There is no heart involvement;
• it is caused by abnormalities in the SMPX gene, on the X chromosomeForme que prend l’ADN pendant la division cellulaire (aspect de fins bâtonnets). Il est composé de 2 bras, un bras long et un bras court. Par convention, le bras long s’appelle q, et le bras court s’appelle p. Chez l’être humain, il y a 23 paires de chromosomes (soit 46 chromosomes). Vingt-deux paires sont constituées de 2 chromosomes identiques, appelés autosomes. La vingt-troisième paire est constituée des chromosomes sexuels, XX chez la femme et XY chez l’homme.;
• thanks to muscle MRI and histopathology, it was possible to describe the characteristics common to these patients, such as sarcoplasmic inclusions.

This condition was identified in 5 different countries, and researchers are suggesting that cases exist in all populations, with a probable founder effect in France and in southern Europe. The abnormalities in the SMPX gene still need to be researched, especially among the small number of male cases, for which biopsy suggests a myofibrillar myopathy.

Missense mutations in small muscle protein X-linked (SMPX) cause distal myopathy with protein inclusions. JJohari M, Sarparanta J, Vihola A, Jonson PH, Savarese M, Jokela M, Torella A, Piluso G, Said E, Vella N, Cauchi M, Magot A, Magri F, Mauri E, Kornblum C, Reimann J, Stojkovic T, Romero NB, Luque H, Huovinen S, Lahermo P, Donner K, Comi GP, Nigro V, Hackman P, Udd B. Acta Neuropathol. 2021 Aug;142(2):375-393.