Résumé :
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Nemaline myopathy (NM) is a rare congenital myopathy characterized by muscle weakness and the presence of nemaline (rod) bodies in the muscle fibers. NM is a genetically heterogeneous condition of which rigid spine syndrome is a rare feature. Here we describe a sib pair from a consanguineous family. Their motor development was normal, and presentation was at ages 12 years and 6 years with axial myopathy, limitation in flexion of the cervical and dorsolumbar spine and restrictive respiratory insufficiency. The patients did not show limb or facial weakness, smallness of muscle bulk or joint contractures. Scoliosis and severe retrocollis were noted in the elder sib who died at 14 years during acute respiratory infection. CK levels were normal. Electromyography showed a myogenic pattern in the deltoid muscle. Cardiac investigations revealed no abnormality. Biopsy of the deltoid muscle with Gomori trichrome method showed nemaline bodies in subsarcolemmal region of the muscle fibers in both children. There is uniformity of type 1 fibres and absence of type 2 fibres in the first one, predominance of type 1 fibres, fibre type disproportion and incomplete differentiation of fibre types in the younger. Linkage analyses and/or sequencing excluded the six known NM genes ACTA1, NEB, TPM2, TPM3, TNNT1 and CFL2 and also the following candidate genes: SEPN, TTN, DES, MYOT and RYR. In conclusion, further linkage and sequencing studies are warranted to identify the causative genetic defect in this familial case of nemaline myopathy with rigid spine.
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