Skip to content
left end
left end
right end

Myopathy - muscle weakness

Skeletal myopathy, proximal myopathy (weak muscles)

Easy fatigue and lethargy

Abnormal mitochondrial functiontests/abnormal respiratory chain tests 

Abnormal muscle biopsies

Idiopathic mitochondrial disease, i.e. unexplained mitochondrial disease

Many boys with Barth Syndrome have DELAYED MOTOR MILESTONES early in life, e.g. being slow to stand or run, although this does not affect all patients. It eventually becomes clear that motor delay is due to muscle weakness, especially affecting the large muscles of the thigh. Weakness is often accompanied by LETHARGY and easy FATIGUE, particularly affecting stamina, and the ability to exercise or to play sport. Boys may have difficulty getting up from sitting on the floor (called a "positive Gower's sign") or kicking a football. They may take several days to recover from a period of more strenuous exercise.

These problems are usually diagnosed as "myopathy" or "proximal myopathy", and may be investigated by a muscle biopsy in order to determine whether there is a problem with the mitochondria (the powerhouses which supply energy to cells). The appearance of the mitochondria will be examined by electron microscopy and "mitochondrial function"/"respiratory chain function" tests are often performed on these muscle biopsies. In Barth Syndrome the mitochondrial appearance ranges from normal to very abnormal, as do mitochondrial function tests.

Barth Syndrome should therefore be suspected in any boy who has proximal myopathy or "mitochondrial disease" but where it has not been possible to determine the exact genetic cause. This suspicion should be particularly strong where there is a family history of males on the female side of the family having any of the other features described in this section.

It is important to note that Barth Syndrome can be excluded rapidly via the Barth Syndrome Service in Bristol, at no cost to referring clinicians from the UK, by a biochemical cardiolipin assay on 2-3ml of blood in an EDTA (full blood count) tube.This may avoid muscle biopsy which can leave a depression and large scar in the thigh of a male when they are fully grown. Important addresses and contact numbers for testing procedures are given here.