CENTRONUCLEAR CONGENITAL MYOPATHY: THE PREDOMINANT SUBTYPE IN THE WESTERN CAPE OF SOUTH AFRICA

Objectives: Congenital myotubular myopathy consists of X-linked neonatal and autosomal recessive centronuclear forms. Objective: To review the clinical phenotype and course of children with histological confirmation of centronuclear myopathy.

Methods: The subgroup of all patients with congenital myopathy or dystrophy were retrospectively selected and clinical phenotype and muscle biopsy immunohistopathology defined.

Results: Between 2000 and 2005, 274 new patients attended the neuromuscular clinic. Nine had congenital muscular dystrophy; 23 had congenital myopathies consisting of nemaline myopathy (n=3), minicore disease (n=1), central core disease (n=1), Bethlem myopathy (n=1), centronuclear myopathy (n=15) and non-specific myopathy (n=2). Of the 15 patients with centronuclear myopathy (9 male: 6 female) median age was 89 months (range of 15–292 months). Patients had similar phenotypic appearance with myopathic facies, carp shaped mouths, external ophthalmoplegia (n=14), ptosis, proximal weakness, hypotonia and hyporeflexia or areflexia. All were symptomatic from birth and nine had reduced in utero movements recorded. Patients had poor oro-motor control leading to feeding difficulties. Lower respiratory tract infections were common. All children attained sitting (median 11 months, range 9–18 months) but only six children walked (median 18 months, range 17–60 months). Intellect was normal or above average in all. Muscle biopsy was performed between 5–65 months (median 12 months). Histopathology showed fibre type disproportion, central nuclei and Z band streaming. Variable features were splitting, ring fibres, fibrosis and adipose infiltration.

Conclusion: Centronuclear myopathy was the predominant congenital myopathy subtype in the Western Cape. Although profoundly weak at birth patients followed a relatively benign course with functional improvement.