DOK7 limb-girdle myasthenic syndrome mimicking congenital muscular dystrophy

Congenital myasthenic syndrome shows a wide clinical heterogeneity. However, the unusual pattern of muscle weakness and the presence of variable degree of muscle pathology, subtle electrophysiological abnormalities and lack of circadian variability of symptoms may complicate its recognition. We have previously reported a Palestinian family with suspected congenital muscular dystrophy and linkage to chromosome 4p16.3. As the DOK7 gene is located in this genetic interval, we considered it a potential candidate for this condition. Patients showed a homozygous DOK7 pathogenic mutation (c.957delC). We have re-examined six patients and found permanent limb-girdle weakness, but also episodic crises without clear precipitating factors. Following the revised diagnosis, patients were treated with salbutamol for 8 months with significant improvement in their muscle strength and function. This family needs to be reclassified as congenital myasthenic syndrome rather than congenital muscular dystrophy.