Elevated Serum CK Research Articles

Myoglobin is a sensitive marker of increased muscle membrane vulnerability

Changes in muscle proteins in serum after exercise were studied to evaluate the use of such proteins as indicators of increased muscle membrane vulnerability. Seventy-one women were asked to perform bicycle exercise for 45 min at a moderate load; four proteins (creatine kinase - CK, myoglobin - Mb, aldolase - Ald and pyruvate kinase - PK) were measured in serum up to 24 h after exercise. Twenty-one women were carriers of Duchenne's muscular dystrophy (DMD); these are known to show an elevated serum CK activity at rest, as well as increased CK response after exercise. Fifty women without a family history of neuromuscular disease were tested to obtain normal values: they showed a small peak (18%) of CK activity 8 h after exercise, and an even smaller peak of Mb (9%) 1 h after exercise. The mean post-exercise increase for both CK and Mb in the 21 DMD carriers was significantly higher than in controls; the maximum of Mb, on average 70% of baseline levels, was reached 1 h after exercise and was higher than that for CK (48%), which was reached 8 h after exercise. It is concluded that myoglobin levels after exercise are a good index of increased vulnerability of the muscle membrane.

Glycogen storage disease with normal acid maltase: Skeletal and cardiac muscles

We report a 5-year-old boy with lysosomal glycogen storage disease and normal acid maltase activity. This patient, the fourth reported in the literature, was referred to our hospital for evaluation of elevated serum GOT, GPT, and CK activities. He had neither muscle weakness nor atrophy. Echocardiography demonstrated marked thickening of the intraventricular septum and left ventricular wall which indicated hypertrophic cardiomyopathy. Biopsied skeletal muscle disclosed massive accumulation of glycogen and autophagic vacuoles. Electron microscopy of biopsied cardiac muscle revealed severe myofibrillar disruption with marked accumulation of free and intralysosomal glycogen. Activities of all major glycolytic enzymes in skeletal muscle, including acid maltase, were normal. It is unknown why muscle lysosomes appeared to be unable to digest the trapped glycogen despite the presence of acid maltase. Our findings illustrate the importance of performing skeletal muscle investigation during childhood in patients with hypertrophic cardiomyopathy.

Elevated Atypical Creatine Kinases

To the Editor.— We read with interest the CASE REPORT of a patient with metastatic adenocarcinoma of the lung and elevated serum CK isoenzyme with an electrophoretic pattern consistent with the MB fraction. 1 We have reported a similar case of a patient with metastatic oat cell carcinoma who had persistent elevation of the serum CK with isoenzyme fractionation showing CK-MB in the range of 47% to 53% and CK-BB in the range of 11% to 23%. 2 At postmortem examination, there was no evidence of myocardial injury. Of interest, however, was that measurement of CK isoenzymes in the patient's tumor tissue showed 46% MB, 44% BB, and only 9% MM, while the myocardium showed 93% MM and 7% MB fraction and skeletal muscle 97% MM and only 3% MB fraction. Although the nature and mechanisms of production of these CK isoenzymes by malignant tissue remain unclear, we demonstrated that

Congenital myopathy and communicating hydrocephalus - A possible pathogenetic combination

A 5 1/2-year-old boy with congenital myopathy associated with communicating hydrocephalus is described. Motor milestones were delayed with generalized nonprogressive muscular weakness and moderately elevated serum CK. Muscle biopsy revealed multifocal areas of decreased oxidative enzyme activity which were characterized ultrastructurally by myofibrillar disorganization and Z-band streaming with decrease or absence of mitochondria in this area. The head circumference measured more than 98 percentile at 14 months. The CT scan disclosed moderately dilated ventricles and enlarged cortical sulci. Radioisotope cisternograms showed early ventricular reflux and persistence of radioactivity especially in the parasaggital region even after 72 hours. Some common pathogenetic mechanism may have been involved in the development of both the myopathy and the hydrocephalus.

Serum and urinary myoglobin in alcoholics.

The serum levels of myoglobin were measured in 106 male alcoholics. Subnormal levels were found in 31% of the alcoholics with no alcohol consumption for the last 2--4 weeks, while none of them had elevated levels. Of the alcoholics on ambulatory control and with varying current alcohol intake. 18% had increased levels compared to healthy controls. Serial myoglobin levels were determined in 19 patients following the cessation of heavy drinking sprees. Despite the fact that none of the patients had clinical evidence of acute myopathy, marked myoglobin elevations were noted in five patients; their serum levels gradually declined and normalized with 4--7 days. Comparing the three groups, similar frequencies of subnormal or elevated serum CK levels were observed. Myoglobin levels were not raised due to impaired glomerular filtration rates. No correlation was found between serum myoglobin and laboratory signs of liver affection. Although hypophosphatemia, hypomagnesemia and hypokalemia were occasionally noted, decreased serum electrolytes did not have any relation to elevated serum myoglobin. A transient, slightly increased urinary excretion of myoglobin parallel with increased excretion of beta 2-microglobulin was observed in 2/17 alcoholics, suggesting that instances of myoglobinuria in alcoholics with heavy recent drinking may be due to a transient minor tubular dysfunction.

Spinal muscular atrophy and hypertrophy of the calves

In 100 patients (59 males and 41 females) suffering from proximal spinal muscular atrophy, 23 presented with hypertrophy of the calves. These were all males. They all showed an elevation of serum CK-activity. The combination of spinal muscular atrophy, hypertrophy of the calves and elevated serum CK activity was not found in females.