G.P.63 - Musculoskeletal function in children with Barth syndrome

Abstract

Barth syndrome (BTHS) results from an X-linked recessive defect in the TAZ gene. It typically presents in males with dilated cardiomyopathy, intermittent neutropenia, growth delay, distinctive facial features, skeletal muscle weakness and fatigue. Definitive testing for the disease is possible by assessment of the ratio of mitochondrial membrane cardiolipin to monolysocardiolipin in blood cells. In 2010, an NHS Specialised Service for the disease was established in Bristol, UK. This study describes the systematic assessment of skeletal muscle function in this UK cohort of 23 children with BTHS. All of the cohort had assessments of strength (North Star protocol), joint range, spinal and foot posture. They had annual videos of their gait and run. Children under 4 years were assessed with Bayley developmental scales. Our main findings are that these males with BTHS have reduced strength and endurance. This weakness was largely in the more proximal muscle groups but was also noted distally, particularly in their calf muscles. They had reduced grip strength, and this was particularly evident with a sustained hold. They tended to have flexible joints with some being very hypermobile. Some muscle tightness was present but there were no contractures. Due to their weakness and joint laxity the boys have an abnormal gait. They tend to have a reduced push off, especially noticeable when running. They find it difficult to walk/run in a straight and controlled way and often use their arms to help with propulsion and to stabilise. They have great difficulty with change of direction. A large proportion of the boys also present with some sensory impairment which has an effect on their gait and every day functioning. Some males, with an intermediate biochemical form of BTHS, have good exercise tolerance. We conclude that our cohort of patients with BTHS has abnormal skeletal muscle strength and mass which leads them to have a distinctive pattern of function, strength and gait.