Description of a second form of DNAJB4-related myopathy

Two months after the publication of a new DNAJB4-related myopathy in four patients, a Japanese-American study describes six more patients with another, as yet unreported, form.

The study of patients with this new form reveals:

• a heterozygous mutationModification soudaine et transmissible du matériel génétique. Elle peut être spontanée ou induite par des agents dits » mutagènes » (radiations, produits toxiques,…). (c.270 T > A) of the DNAJB4 gene ;
• an autosomal dominantEn génétique, c’est la caractéristique d’un individu qui n’a besoin que d’un seul exemplaire d’un certain gène (allèle) pour s’exprimer. Cet exemplaire unique peut venir du père ou de la mère. mode of transmission;
• an onset during the 3rd to 5th decade;
• an elevated CPKEnzyme contenue dans les cellules musculaires, qui est libérée dans le sang en cas d’atteinte musculaire. level;
• a predominantly distal presentation, with weakness and atrophy, possibly asymmetric, of calf muscles (gastrocnemius, soleus) and of the hand (thenar and hypothenar areas);
• a progression towards damage to the proximal muscles (long and large adductors, biceps femoris, etc.) and respiratory insufficiency;
• selective and predominant involvement of muscles composed mainly of type 1 fibres.

While they were observed in the first form, none of the patients in this study had spinal rigidity, weakness of the trunk muscles, or cardiomyopathy.

Distinctive chaperonopathy in skeletal muscle associated with the dominant variant in DNAJB4. Inoue, M., Noguchi, S., Inoue, Y. U. et al. Acta Neuropathol 2022.