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 mutation (c.270 T > A) of the DNAJB4 gene ;
- an autosomal dominant mode of transmission;
- an onset during the 3rd to 5th decade;
- an elevated CPK 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.
