Biochemical investigation of muscle disease

Use of dynamic tests of muscle function and histomorphometry of quadriceps muscle biopsies in the investigation of patients with chronic alcohol misuse and chronic fatigue syndrome

Ischaemic lactate/ammonia tests, serum carnosinase and creatine kinase assays and percutaneous needle muscle biopsies were performed on 10 patients with chronic fatigue syndrome (CFS), and 10 with chronic alcohol misuse complaining of muscular symptoms. Basal serum lactate levels were significantly elevated in the alcohol misusers compared to the CFS patients, but all were within the reference range. Lactate profiles after ischaemic forearm exercise did not differ significantly for the two patient groups. In one patient previously diagnosed as having CFS, myoadenylate deaminase deficiency was identified on the basis of a flat ammonia response to ischaemia and absent muscle adenosine monophosphate deaminase activity. In addition, two further patients in the CFS group were subsequently shown to have other disorders: one had polymyositis and one had myopathy with mild type II fibre atrophy of unknown cause. Histomorphometric examination of muscle needle biopsy in the alcohol misusers showed features of chronic alcohol-induced skeletal myopathy in six patients and polymyositis in one patient. Type II fibre atrophy factors were significantly elevated in the alcohol group but were within the reference range in CFS patients. Dynamic tests of muscle function and muscle histology are valuable tools in excluding alternative pathology in CFS, whereas muscle histomorphometry is of the greatest value in the diagnosis of chronic alcoholic myopathy.

Becker muscular dystrophy: an unusual presentation

A 15 year old boy who presented with passing painless dark urine was found to have myoglobinuria. His creatine phosphokinase was raised, and a muscle biopsy specimen showed non-specific dystrophic changes. Subsequent DNA analysis led to the diagnosis of Becker muscular dystrophy. Myoglobinuria may be a presenting symptom of Becker muscular dystrophy.

[Diagnosis of muscular intolerance during exercise caused by enzyme deficiency in adults]

The exertional muscle pain syndrome in adults is expressed by recurrent episodes of pain and/or episodes of acute rhabdomyolysis, sometimes with transient myoglobinuria or even acute renal failure. The enzymatic origin of this syndrome is suggested by a familial history, by its usual onset during childhood or adolescence, and by its recurrent attacks usually, but not exclusively, caused by exercise. The aetiological diagnosis, suggested by the clinical context and some dynamic tests, is almost always based on good histological and biochemical examinations of the muscle biopsy.

The measurement of the rotenone-sensitive NADH cytochrome c reductase activity in mitochondria isolated from minute amount of human skeletal muscle

Mitochondria isolated from minute amounts (100-500 mg) of human skeletal muscle displayed a very high rotenone-resistant NADH cytochrome c reductase activity. Moreover, compared to succinate cytochrome c reductase activity, a low rate of rotenone-sensitive NADH cytochrome c reductase activity was measured when using standard procedures to disrupt mitochondrial membranes. Only a drastic osmotic shock in distillated water as a mean to disrupt mitochondrial membrane was found to strongly increase the actual rate of the rotenone-sensitive activity. This was accompanied by a decrease in the rotenone-insensitive activity. Using such a simple procedure, the NADH cytochrome c reductase was found 70-80% inhibited by rotenone and roughly equivalent to 70-85% of the activity of the succinate cytochrome c reductase.