Myoadenylate deaminase deficiency with severe rhabdomyolysis

Metabolic myopathies: update 2009

Metabolic myopathies are inborn errors of metabolism that result in impaired energy production due to defects in glycogen, lipid, mitochondrial, and possibly adenine nucleotide metabolism. Fatty acid oxidation defects (FAOD), glycogen storage disease, and mitochondrial myopathies represent the 3 main groups of disorders, and some consider myoadenylate deaminase (AMPD1 deficiency) to be a metabolic myopathy. Clinically, a variety of neuromuscular presentations are seen at different ages of life. Newborns and infants commonly present with hypotonia and multisystem involvement (liver and brain), whereas onset later in life usually presents with exercise intolerance with or without progressive muscle weakness and myoglobinuria. In general, the glycogen storage diseases result in high-intensity exercise intolerance, whereas the FAODs and the mitochondrial myopathies manifest predominately during endurance-type activity or under fasted or other metabolically stressful conditions. The clinical examination is often normal, and testing requires various combinations of exercise stress testing, serum creatine kinase activity and lactate concentration determination, urine organic acids, muscle biopsy, neuroimaging, and specific genetic testing for the diagnosis of a specific metabolic myopathy. Prenatal screening is available in many countries for several of the FAODs through liquid chromatography-tandem mass spectrometry. Early identification of these conditions with lifestyle measures, nutritional intervention, and cofactor treatment is important to prevent or delay the onset of muscle weakness and to avoid potential life-threatening complications such as rhabdomyolysis with resultant renal failure or hepatic failure. This article will review the key clinical features, diagnostic tests, and treatment recommendations for the more common metabolic myopathies, with an emphasis on mitochondrial myopathies.

Sports and performing arts medicine. 1. general considerations for sports and performing arts medicine11A commercial party with a direct financial interest in the results of the research supporting this article has conferred or will confer a financial benefit upon the author or one or more of the authors. Nadler is a consultant for Proctor & Gamble

This self-directed learning module highlights general considerations in sports and performing arts medicine. It is part of the study guide on sports and performing arts medicine in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation.

OVERALL ARTICLE OBJECTIVE

To discuss similarities and differences of injuries sustained in sports and performing arts using case vignettes.

Myoadenylate deaminase deficiency with progressive muscle weakness and atrophy caused by new missense mutations in AMPD1 gene: case report in a Japanese patient

A 46-year-old woman with exertional myalgia developed slowly progressive weakness in her lower extremities. She had slight muscle weakness in her facial and upper extremities, and severe muscle weakness and atrophy in lower extremities more marked in the proximal portions. Serum creatine kinase was slightly elevated. After ischemic forearm exercise test, blood ammonia had no elevation although lactate level increased normally. The computed tomography revealed that a characteristic distribution of skeletal muscle involvement with proximal and flexor muscles more severely affected than distal and extensor in the lower extremities. In addition, the left sternocleidomastoid muscle showed marked atrophy with an asymptomatic weakness of over 20 years duration suggesting abnormal development. Needle EMG examination showed a large number of easily recruited, short-duration, low-amplitude motor unit potentials in all extremities. Muscle biopsy showed absence of adenosine monophosphate deaminase activity with normal cytochrome c oxidase and phosphorylase activity. With the muscle enzyme activity assay, adenosine monophosphate deaminase activity was found to be lower than 0.2% of the controls. The DNA analysis revealed that she was compound heterozygote involving two missense mutations (R388W and R425H) in exon 9 and exon 10 of AMPD1 gene. This is the first report of primary myoadenylate deaminase deficiency with progressive weakness and atrophy caused by novel compound heterozygous mutations of AMPD1 gene, and suggests that adenosine monophosphate deaminase is closely related not only to energy metabolism but also to the development of skeletal muscle.

Metabolic causes of recurrent rhabdomyolysis

OBJECTIVES

The aim of the study was to evaluate the biochemical causes of recurrent rhabdomyolysis in Finland.

MATERIAL AND METHODS

We examined 22 patients with recurrent rhabdomyolysis, and 26 patients with one episode of rhabdomyolysis or other symptoms compatible with metabolic myopathy. Muscle histopathology and activities of phosphorylase (PHRL) (total and active), phosphofructokinase (PFK), carnitine palmitoyltransferase (CPT) and myoadenylate deaminase (MAD) were studied. The limit of enzyme deficiency was defined as enzyme activity less than 5% of the mean of the control subjects.

RESULTS

We found 4 patients with muscle PHRL deficiency, 1 patient with PFK deficiency and 1 patient with evidence of phosphorylase kinase deficiency. One patient had Becker's muscle dystrophy, 2 patients had unspecified dystrophies, 1 patient had Miyoshi myopathy, and 1 patient had a form of mitochondrial encephalomyopathy (MELAS).

CONCLUSION

Enzyme defects were found in 23% of the patients with recurrent rhabdomyolysis. Other muscle diseases, muscular dystrophies or myopathies, were detected in 18% of these patients, emphasizing the value of clinical and histopathological examination of patients with previous rhabdomyolysis.

Tension myalgia versus myoadenylate deaminase deficiency: a case report

Myalgia is a complaint associated with numerous medical conditions such as metabolic or hormonal abnormalities, toxic myopathies, tetanus, electrolyte disturbances, inflammatory diseases, and exertion-related pain. A diagnosis of tension myalgia or myofascial-type pain is often considered when no objective findings are seen in the evaluation. This is a report of a patient who was treated unsuccessfully for fibromyalgia for many years and who ultimately was diagnosed with a rare benign skeletal muscle metabolic disorder caused by myoadenylate deaminase deficiency. We discuss this enzyme deficiency and its importance for the physiatric community.