French clinicians report, in five patients with congenital rod myopathy (also called nemaline), histological lesions in the form of dense protein masses:
- none of the patients were related,
- in three of them pathological variants of the NEB gene encoding nebulin were identified,
- in another, the TPM2 gene encoding tropomyosin-2 was involved,
- the clinical phenotype was not specific with global motor deficit and moderate restrictive pulmonary syndrome, without associated cardiac involvement,
- the dense masses observed by electron microscopy were composed of Z-streak sarcomeric proteins and were different from rods.