Myoadenylate deaminase deficiency: diagnosis by forearm ischemic exercise testing

Diagnostic utility of a modified forearm ischemic exercise test and technical issues relevant to exercise testing

The sensitivity and specificity of a modified forearm ischemic test (FIT) are described in the diagnosis of glycogen storage disease, myoadenylate deaminase deficiency, and mitochondrial disease. FIT and muscle biopsy results were reviewed from 99 patients (glycogen storage disease [GSD], myoadenylate deaminase deficiency [AMPD], mitochondrial disease [MITO], miscellaneous neuromuscular disorders, and controls). The influence of catheter placement and an antecedent sugar bolus were also assessed in healthy young men. The FIT had a sensitivity of 1.00 and a specificity of 1.00 for a diagnosis of GSD, whereas the corresponding values were 1.00 and 0.37 for AMPD deficiency. A baseline lactate of >2.5 mmol/L provided the highest sensitivity (0.62) and specificity (1.00) for MITO disease. A baseline and +1 min sample provided optimal sensitivity and specificity for GSD and AMPD deficiency. Catheter placement in any vein other than the ipsilateral antecubital resulted in attenuated lactate responses (P < 0.0001). A pre-FIT sugar bolus did not alter the postexercise lactate or ammonia response. Thus, a modified FIT was helpful in the diagnosis of GSD and excluding AMPD deficiency, but not in the diagnosis of MITO disease. Catheter placement is critical to the interpretation of a FIT, whereas pretesting diet is less important.

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.

Myoadenylate deaminase deficiency with severe rhabdomyolysis

A 13-year-old Turkish girl was admitted because of recurrent episodes of muscle pain and weakness since the age of 5 years. As an outpatient she developed severe acute rhabdomyolysis (myoglobinuria and increased serum creatine kinase level of 19,000 units/l). The acute rhabdomyolysis and the preceding episodes of muscle pain and weakness had been induced by exercise. There was no increase in plasma ammonia level during ischaemic forearm exercise test and bicycle ergometry. Myoadenylate deaminase deficiency was proven both histochemically and biochemically. The girl was found to be homozygous for the C 34-T mutation of the AMPD1 gene causing primary myoadenylate deaminase deficiency in skeletal muscle. Both parents and her brother were heterozygous for that mutation. Myoadenylate deaminase deficiency has to be considered as a cause of severe rhabdomyolysis.

Myoadenylate deaminase deficiency

Myoadenylate deaminase (MAD) is the rate-limiting enzyme in the purine nucleotide cycle which is biochemically linked to glycolysis and the citric cycle and thereby providing energy during intense muscular activity. In muscle fibers, myoadenylate deaminase operates at considerably higher activity levels than in other organs. First detected using enzyme-histochemical methods, it now appears that deficiency of myoadenylate deaminase is one of the most frequent enzyme defects in muscle. The primary defect may occur as an isolated nosological entity or not infrequently it is also associated with a large spectrum of different neuromuscular conditions. It seems to be the primary unassociated MAD deficiency that has recently become amenable to successful treatment with D-ribose in high doses. Secondary MAD deficiency may occur in muscle fibers and muscles that have undergone structural damage as seen, for instance, in polymyositis, muscular dystrophy, and denervation. The wealth of biochemical, morphological, and clinical data that has accumulated since the discovery of MAD deficiency during the past decade provides nosological significance of MAD deficiency as a real entity.

Myoadenylate deaminase deficiency: successful symptomatic therapy by high dose oral administration of ribose

A 55 years old patient suffering from exercise-induced muscle pain and stiffness due to primary myoadenylate deaminase deficiency has been successfully treated with D-ribose since 1984: single doses of 4 grams administered at the beginning of exercise prevented the symptoms completely; on continuation of exercise this dose had to be repeated all 10-30 min. Total doses of 50-60 g per day were tolerated without side-effects.