[Congenital muscular dystrophy and merosin deficiency]

Merosin alpha 2 chain, an extracellular matrix protein, is deficient in a proportion of patients with classical congenital muscular dystrophy (CMD). A study of clinical, laboratory and histopathological features of 18 patients with CMD was performed in relation to the merosin expression in muscle biopsy. Immunohistochemistry study showed that merosin was deficient in 11 patients and present in 7. None of the 9 merosin-deficient patients evaluated achieved walking. In contrast, 4 of 7 merosin-positive patients achieved independent ambulation. Creatine kinase levels were higher in merosin-deficient patients, but this difference was not statistically significant. Motor nerve conduction study was carried out on 12 children. All 4 merosin-positive patients had normal exams whereas 2 out 8 merosin-deficient patients presented decreased motor nerve conduction velocity. Among 69 histopathological features studied, we did not find any significant difference between merosin-deficient and merosin-positive patients. These results suggest that merosin status evaluation is important in the determination of the prognostic, since merosin-positive patients can achieve independent walking. This study also suggests that there is no relation between absence of merosin and histopathological features.