Serum enzyme studies in acquired disease of skeletal muscle

Natural History of Serum Enzyme Levels in Duchenne Muscular Dystrophy and Implications for Clinical Practice

OBJECTIVE

In Duchenne muscular dystrophy, creatine kinase and transaminases are released into the circulation, indicating muscle injury. Their usefulness in monitoring muscle injury or disease progression has not yet been fully evaluated. Thus, this study examined serum creatine kinase and transaminase concentrations at different ages in patients with Duchenne muscular dystrophy and evaluated their association with muscle injury.

DESIGN

This is a prospective cohort study that included 110 patients with Duchenne muscular dystrophy categorized by age groups. Creatine kinase and transaminases were quantified in the serum; the Vignos scale evaluated the muscle function.

RESULTS

Creatine kinase and transaminase levels were higher in ambulatory than that in nonambulatory patients, which significantly decreased as age increased. Serum creatine kinase and transaminase concentrations were elevated in all ages, and those aged 3-4 yrs had the highest concentrations. Age and Vignos Scale were significantly correlated with creatine kinase and transaminase concentrations. Age, creatine kinase, and transaminases explained the 42.5% of loss of muscle function.

CONCLUSIONS

This study added the knowledge on the natural history of Duchenne muscular dystrophy at different ages and confirmed that creatine kinase and transaminases decrease with age and loss of muscle function, making them generally inappropriate for monitoring response to therapy, although they are useful for the clinical diagnosis.

X-linked recessive (Duchenne) muscular dystrophy (DMD) and purine metabolism: effects of oral allopurinol and adenylate

Data are presented which suggest that Duchenne muscular dystrophy (DMD) may have some origin in a severe deficiency of total muscle adenine nucleotides. Using double-blind techniques, this possibility was tested in 16 DMD patients by giving oral allopurinol, a synthetic inhibitor of the purine catabolic enzyme xanthine oxidase. Sublingual procaine adenylate was also briefly tested. Instances of clinical improvement quickly occurred which were statistically significant; they were accompanied by a significant increase in physical strength. These improvements have been maintained for more than 6 mo by administration of a small amount of allopurinol daily. Procaine adenylate had little effect. These results support the above view of DMD and seem to indicate that existing purines, retained and recycled after allopurinol, can sustain such improvement, and that additional adenylate is unnecessary.

Studies on the carrier state in X-linked recessive (Duchenne) muscular dystrophy

Observations in 12 normal women and 12 female carriers of X-linked recessive Duchenne muscular dystrophy (DMD), of whom 4 had symptoms and 8 had none, were compared between all 4 groups and with those in 2 DMD boys, one active and one crippled. Carrier symptoms were readily ascertained by systematic examination. Measurement of both lower legs in all 24 women showed neither calf enlargement nor asymmetry in carriers beyond normal variation. Two DMD carrier daughters were noted of the same DMD carrier mother but by different fathers. Whole body counting showed the biological half-life of previously administered 86Rb to be much reduced in DMD, but no differences were found between normal women and any group of carriers. The test is thus valueless for carrier detection, and reasons are given why it should be so. Simultaneous measurement of total body K+, with subsequent determination by isotope dilution of total body water as 3H2O space and extracellular water as NH4 82Br space, showed increased intracellular water and reduced intracellular K+ concentration in all carriers, as if due to osmotic causes, with actual loss of muscle mass and slight diminution of serum K+ in the 4 symptomatic carriers only. Because of diurnal and other variations, the means and standard deviations for six serum enzymes from six fortnightly assays in all subjects were used to measure precise individual status. Their coefficients of variation were abnormal only in symptomatic carriers and ambulant DMD, easily overtexed by even accustomed exertion. This is shown to support previous propositions on the pathogenesis of DMD and the escape of muscle cell content into the circulation.