[Late myopathies located at the spinal muscles: a cause of acquired lumbar kyphosis in adults].

A primary myopathy limited to the spinal muscles and of late onset was suspected in 14 patients with a mean age of 66. These patients had an anterior inflection of the trunk and were unable to rotate the lumbar spine on the pelvis. This incurvation of the trunk, starting at around age 60, was reducible in a horizontal position and increased with tiredness. The CT scan appearance of the spinal muscles of these patients was hypodense and heterogeneous, different from the atrophy found in the elderly with lumbar osteoarthrosis, comparable with the lesions described in primary myopathies. Histologically, lesions of fibro-adiposis were major, accompanied by mitochondrial abnormalities. The frequent existence of a family history would be in favour of a genetically transmitted condition.