P.9.13 Congenital myopathies in a pediatric referral center

Congenital myopathies are a group of inherited neuromuscular disorders presenting in childhood and mainly characterised by muscle biopsy features. Among them, nemaline myopathy, centronuclear/myotubular myopathy and core myopathy are the most common forms. Diagnosis is sometimes challenging since there is clinical and genetic overlap between different forms of congenital myopathies and some genetically confirmed patients may not show typical histopathological findings, at least in early stages. We aimed to document congenital myopathy cases diagnosed in our pediatric center in the last 10 years. We reviewed clinical and histopathological data of cases with a clinicopathological diagnosis of congenital myopathy. Of the 91 cases with a clinical diagnosis of congenital myopathy and compatible muscle biopsy features, mean age of diagnosis was 5 years, ranging from 6 days to 16 years. Classification according to histopathological features yielded 29 cases with nemaline myopathy, 12 myotubular/centronuclear myopathy, 9 core myopathy and 6 congenital fiber type disproportion. In 19 cases, muscle biopsy showed various combination of features compatible with congenital myopathy (increase in central or internal nuclei, uneven staining or core like areas in oxidative enzyme stains, type I fiber predominance) but not sufficient to classify into a typical subgroup. In 16 cases, histological findings were more subtle or showed non-specific myopathic findings. Our results show that nemaline myopathy is the most frequent congenital myopathy in our cohort (31%), while some cases could not be classified solely on histopathological grounds. Molecular analysis, especially in this group of un-classified patients, is important for definite diagnosis and better delineation of milder or earlier histopathological changes.