Evidence of reduced frequency of spinal muscular atrophy type I in the Cuban population.

The authors reviewed all cases of type I spinal muscular atrophy (SMA) in Cuba over a 6-year period. The incidence of SMA type I was 3.53 per 100,000 livebirths. When the population was classified according to self-reported ethnicity, the incidence was eight per 100,000 for whites; 0.89 per 100,000 for blacks, and 0.96 per 100,000 for those of mixed ethnicity. Type 1 SMA may occur less frequently in individuals of African ancestry.

The myopathology of floppy and hypotonic infants in Singapore.

AIMS: This study attempts to determine the type and relative frequency of muscle diseases contributing to floppy and hypotonic infants in Singapore. METHODS: Eighty consecutive muscle biopsies in the Department of Pathology, National University of Singapore, in the period 1978-2000, in which a clinical diagnosis of floppy or hypotonic infant was made, were reviewed. RESULTS: The commonest cause of severe hypotonia in infancy was spinal muscular atrophy, which accounted for 33% of cases followed by congenital muscular dystrophy (13%). Eight cases (10%) of infantile type II glycogenosis (Pompe's disease) were encountered. There were seven cases of congenital myopathy, of which four were centronuclear myopathy, and one each of central core myopathy, nemaline myopathy and congenital fibre type disproportion. One case of centronuclear myopathy was associated with type I fibre smallness. Type II atrophy, which is generally considered a non-specific change, was encountered in five cases. Of interest is the relatively large number of muscle biopsies (29%) in which no significant pathological features were encountered at the light microscopic, histochemical as well as ultra-structural level. CONCLUSIONS: The study has revealed a great variety of pathology affecting the muscle of children presenting as floppy infants or with hypotonia. The muscle diseases included spinal muscular atrophy, congenital muscular dystrophies, congenital myopathies and metabolic myopathies. However, 23 (29%) cases showed no significant pathology. For this group of floppy and hypotonic infants further studies are needed.

Spinal muscular atrophy in African children.

Forty-five African children with SMA were seen over a period of five years. Fifteen had severe infantile form (Group 1), 19 intermediate (Group 2), 9 juvenile (Group 3) and 2 cervical type. A positive family history was obtained in only 9% of patients. The female/male ratio was 1:1.7. The age of onset was under four months in Group 1, between 5-24 months in Group 2. In 77% of Group 3 onset was between 5-24 months, 22% between 25-48 months. The lower limbs were more severely affected than upper limbs in all except the two patients with cervical SMA, proximal muscles more than distal in 82% and proximal and distal muscle were equally affected in 18%. Bulbar weakness was present in 73% and facial weakness in 80% of Group 1 patients only. Fasciculation of tongue occurred in 50% of Group 1, 42% of Group 2 and 44% of Group 3 patients. Tremor of hands was seen in none of the patients in Group 1, 58% in Group 2 and 66% in Group 3. Tendon reflexes were absent or depressed in all except one patient in Group 2 and were normal in the legs of the two patients with cervical SMA. The blood CK was elevated in 26% of patients. An ECG "tremor" was present in 26% of patients in Group 1, 68% in Group 2 and 66% in Group 3. Four patients (all in Group 1) died of pneumonia; the outcome in the others is not known.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of immunoregulatory cells in Duchenne muscular dystrophy and spinal muscular atrophy among African and Indian patients.

Suppressor cells were assayed by numerical and functional tests in Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA) among African and Indian children in order to contribute to an understanding of the pathogenesis of these neurological disorders. Peripheral blood mononuclears (PBM) were classified as total T cells and T cell subsets by the OKT series of monoclonal antibodies and as B cells by the presence of surface immunoglobulin. The suppressive effects of PBM pretreated with concanavalin A (Con A) on normal homologous phytohaemagglutinin (PHA) transformation of mononuclear cells was determined. PBM stimulation by PHA was also assessed. Patients with DMD had a significant increase (P = 0.0353) in the number of T suppressor/cytotoxic cells (1218 +/- 142 cells/mm3, mean +/- SE) as compared to controls (815 +/- 95 cells/mm3) and a significant reduction (P = 0.0282) in OKT4+ cells expressed as a percentage of OKT3+, 50% +/- 3 compared to 61% +/- 3. No differences were detected in any of the numerical assays employed in SMA as compared to controls, or within SMA patients according to severity of disease. Suppressor function and PHA transformation were normal in both groups of patients. No significant correlations were detected between numerical and functional assays of suppression. The implication of the results obtained for the role of immunoregulatory cells in the pathogenesis of DMD in these children is discussed.