Resting muscle pain as the first clinical symptom in children carrying the MTTK A8344G mutation.

The characteristic clinical presentation, especially the appearance of muscle symptoms, is quite unique in children carrying the mtA8344G mutation. The diagnosis of MERRF syndrome is seldom made in the pediatric age. Fatigue is a common finding in children of pubertal age. Fatigue in combination with recurrent resting muscle pain occurs frequently in the initial phase of various hereditary muscle disorders and in several autoimmune, endocrine and metabolic syndromes. In the absence of obvious biochemical/metabolic abnormalities and in the lack of neurological symptoms the complaints are frequently labelled as fibromyalgia or chronic fatigue syndrome. In patients with behavioural or psychiatric abnormalities one might even start to question the organic etiology of the complaints. We describe a family carrying the classic MTTK mutation with a variable degree of heteroplasmy, presenting in childhood as isolated recurrent muscle pain as the first symptom of the disease.