Immunohistochemical alterations of dystrophin in congenital muscular dystrophy

Limb-girdle muscular dystrophy: an immunohistochemical diagnostic approach

The limb-girdle muscle dystrophy (LGMD) represents a heterogeneous group of muscular diseases with dominant and recessive inheritance, individualized by gene mutation. A group of 56 patients, 32 males and 24 females, with suggestive LGMD diagnosis were submitted to clinical evaluation, serum muscle enzymes, electromyography, muscle biopsy, and the immunoidentification (ID) of sarcoglycans (SG) alpha, beta, gamma and delta, dysferlin and western blot for calpain-3. All the patients had normal ID for dystrophin (rod domain, carboxyl and amine terminal). The alpha-SG was normal in 42 patients, beta-SG in 28, beta-SG in 45, deltaSG in 32, dysferlin in 37 and calpain-3 in 9. There was a reduction in the alpha-SG in 7 patients, beta-SG in 4, gamma-SG in 2, and delta-SG in 8. There was deficiency of alpha-SG in 7 patients, beta-SG in 6, gamma-SG in 9, delta-SG in 5, dysferlin in 8, and calpain-3 in 5. The patients were grouped according the ID as sarcoglycans deficiency 18 cases, dysferlin deficiency 8 cases and calpain-3 deficiency 5 cases. Only the sarcoglycans deficiency group showed calf hypertrophy. The dysferlin deficiency group was more frequent in females and the onset was later than sarcoglycan and calpain-3 deficiency groups. The calpain-3 deficiency group occurred only in males and showed an earlier onset and weaker muscular strength.

[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.