Phosphoglycerate mutase deficiency with tubular aggregates in a patient from Panama.

INTRODUCTION: Phosphoglycerate mutase deficiency (PGAM) is a rare metabolic myopathy that results in terminal block in glycogenolysis. Clinically, patients with PGAM deficiency are asymptomatic, except when they engage in brief, strenuous efforts, which may trigger myalgias, cramps, muscle necrosis, and myoglobinuria. An unusual pathologic feature of PGAM deficiency is the association with tubular aggregates. METHODS: We report an African-American patient from Panama with partial deficiency of PGAM who presented with asymptomatic elevation of creatine kinase levels and tubular aggregates on muscle biopsy. RESULTS: Muscle biopsies showed subsarcolemmal and sarcolemmal tubular aggregates in type 2 fibers. Muscle PGAM enzymatic activity was decreased and gene sequencing revealed a heterozygous mutation in codon 78 of exon 1 of the PGAM2 gene, which is located on the short arm of chromosome 7. CONCLUSIONS: PGAM deficiency has been reported in 14 patients, 9 of whom were of African-American ethnicity, and in 5 (36%) tubular aggregates were seen on muscle biopsy. Contrary to previously reported cases, our patient was initially asymptomatic. This further expands the PGAM deficiency phenotype.

Exercise-induced cramp, myoglobinuria, and tubular aggregates in phosphoglycerate mutase deficiency.

We report two patients in whom phosphoglycerate mutase (PGAM) deficiency was associated with the triad of exercise-induced cramps, recurrent myoglobinuria, and tubular aggregates in the muscle biopsy. Serum creatine kinase (CK) levels were elevated between attacks of myoglobinuria. Forearm ischemic exercise tests produced subnormal increases of venous lactate. Muscle biopsies showed subsarcolemmal tubular aggregates in type 2 fibers. Muscle PGAM activities were markedly decreased (3% of the normal mean) and molecular genetic studies showed that both patients were homozygous for a described missense mutation (W78X). A review of 15 cases with tubular aggregates in the muscle biopsies from our laboratory and 15 cases with PGAM deficiency described in the literature showed that this clinicopathological triad is highly suggestive of PGAM deficiency.

McArdle's disease in childhood: report of a new case.

McArdle's disease (glycogenosis type V) is an inherited glycogen storage disease characterized clinically by myalgia, cramps and sometimes myoglobinuria, triggered by exercise. The onset of exercise intolerance is usually in late childhood or adolescence and diagnosis is exceptionally established during infancy. We report the case of a 6-year-old girl who had been complaining of aching muscles for a long time, and who presented after a near-drowning incident, with extensive muscle necrosis, probably secondary to myophosphorylase deficiency-induced cramps. These unusual manifestations led to the diagnosis of this rare disorder. We compare the clinical findings of this case to nine previous reports. This highlights the heterogeneous spectrum of this disease in childhood and supports the distinction of three clinical pictures in childhood: a neonatal form rapidly fatal, a milder form with congenital myopathic symptoms and a benign classical form with myalgia, cramps and pigmenturia.

Molecular genetic studies of muscle lactate dehydrogenase deficiency in white patients.

We identified two new mutations in 2 white patients with muscle lactate dehydrogenase deficiency. Both patients had exercise intolerance, cramps, and recurrent myoglobinuria. One patient was homozygous for a 2-bp deletion in exon 5, resulting in a frameshift with premature termination of translation. The second patient was homozygous for a G-->A substitution at the 3' end of exon 2, leading to exon skipping and splicing of exon 1 to exon 3; the aberrantly spliced messenger RNA contains a frameshift, resulting in premature termination of translation. The present report provides evidence of molecular genetic heterogeneity in white patients with muscle lactate dehydrogenase deficiency.

Ca2+-ATPase deficiency in a patient with an exertional muscle pain syndrome.

31P Magnetic resonance spectroscopy studies were carried out in vivo on skeletal muscle of a patient with verapamil-responsive, chronic, progressive post-exertional muscle pain. A sister suffered from a similar complaint. The results showed that the muscle: (1) decreased its high energy phosphate content more rapidly than normal during exercise, indicating either increased utilisation or decreased production of ATP; (2) acidified more rapidly than normal during exercise suggesting an increased glycolytic rate; (3) continued in some studies to acidify markedly during the first minute after exercise, indicating that glycolysis remained active into the recovery period; (4) had phosphocreatine and ADP recovery rates consistent with normal rates of oxidative phosphorylation. On the basis of these results, it was proposed that the patient suffers from a defect in Ca2+ handling in the muscle. Subsequently, direct measurement of Ca2+-ATPase activity in the sarcoplasmic reticulum fraction from a muscle biopsy sample showed that the activity of this enzyme was reduced by about 90%.

Cramps following exercise.

A 13-year old boy presented with a 10-year history of severe muscle cramps experienced an hour after prolonged exercise. There was no history of exercise intolerance or myoglobinuria. A muscle biopsy showed a lipid myopathy and a deficiency of muscle carnitine palmityl transferase. He has responded to a high carbohydrate, low fat diet with added carbohydrate intake preceding extensive exercise. Diagnosis of this entity before an episode of rhabdomyolysis is unusual.

Adult muscle phosphorylase "b" kinase deficiency.

A 35-year-old man had severe exercise intolerance and cramps. Venous blood lactate did not rise after ischemic exercise, and electromyographically silent contracture of hand muscles appeared. Histochemistry and electronmicroscopy of a muscle biopsy revealed subsarcolemmal and intermyofibrillar accumulation of glycogen. Biochemical studies showed moderately increased amount of glycogen. Total phosphorylase activity was normal, but the active form "a" was 27% of normal. Phosphorylase kinase activity was 12% of the normal value and was normal in leukocytes and erythrocytes.

Type 2 fiber predominance in muscle cramp and exertional myalgia.

In patients complaining of muscle cramps and exertional myalgia, we found a significant decrease of type 1 muscle fiber proportion in comparison with a control group. The possible mechanism of this change is discussed.

Myoadenylate deaminase deficiency in children.

Myoadenylate deaminase (MADA) is an enzyme which participates in the purine nucleotide cycle necessary for energy production in human skeletal muscle. Approximately 35 patients with deficiency of this enzyme have been reported; one-half experienced their initial difficulties in childhood. Children with "primary" MADA deficiency typically have symptoms including muscle cramps, stiffness, and post-exercise myalgia and weakness. In "secondary" MADA deficiency, the clinical findings have been variable with delayed motor development, hypotonia, cardiomyopathy, delayed speech development, and generalized weakness. In most cases creatine kinase determinations, nerve conduction velocity studies, and routine muscle histopathology have been normal. Diagnosis has been established by demonstrating an absence of MADA activity by either direct muscle enzyme assay or histochemical staining. In this report we describe a 12-year-old boy with primary MADA deficiency and contrast his symptoms with those of previously described pediatric patients.

Myoadenylate deaminase deficiency: inherited and acquired forms.

Myoadenylate deaminase deficiency, the most common of the known enzyme deficits of muscle, appears to occur in two forms. The primary type seems to be inherited as a complete gene block in an autosomal recessive pattern. Although occasionally diagnosed in infancy, when muscle biopsy is performed on a hypotonic but normoreflexic child, the deficiency is usually not symptomatic until adult or middle age, when muscle cramping and exercise intolerance develop. The skeletal muscle isozyme is immunologically, and presumably genetically, unique, and these patients have normal levels of adenylate deaminase in their other cells and tissues. A presumptive diagnosis can usually be made by an ischemic forearm exercise test, which shows a negligible increase in blood ammonia, despite a normal rise in lactate. Despite the absence of more than 99% of normal adenylate deaminase activity, the muscle biopsy shows no anatomic pathology, and other enzymes are at normal levels. These patients do not suffer progressive disease, and should be reassured, and encouraged to maintain physical activity. The heterozygous state is probably asymptomatic, except, perhaps, on extreme exercise, but may be associated with an increased incidence of malignant hyperthermia susceptibility. Since the gene defect is not rare, it is not surprising that some cases of the deficiency will be coincidentally associated with other neuromuscular disease. However, there is also a secondary form of myoadenylate deaminase deficiency, consequent to muscle damage from other disease. In this form, the residual activity is higher (1-10% of normal), may present rare foci of positive stain in the section, and reacts normally with antibody to the muscle isozyme. Other muscle enzymes are also depleted, although not as severely, and the prognosis in such cases is dictated by the primary disease. Since the heterozygous state is common, these patients might have been carriers, whose adenylate deaminase levels have been lowered for the deficient category by the advent of other neuromuscular disease.

Selective carnitine palmitoyltransferase deficiency in fibroblasts from a patient with muscle CPT deficiency.

A 13-year-old boy developed cramps and myoglobinuria following exertion. Mitochondrial preparations from a skeletal muscle biopsy were deficient in carnitine palmitoyltransferase (CPT) activity when assayed by the hydroxamate and kinetic assays. The patient's fibroblasts were also deficient when assayed by the hydroxamate and kinetic assays, but not when tested by the DTNB (5,5'-dithiobis-[nitrobenzoic acid]) method. This disparity probably indicates a specific deficiency in fibroblasts of one of the two carnitine palmitoyltransferases, presumably CPT II.

Muscle adenylate deaminase deficiency. Report of six new cases.

We describe six adult patients (five men and one woman) out of 364 whose muscle biopsy specimens disclosed muscle adenylate deaminase deficiency. Two men had an associated dermatomyositis and another man had an associated progressive systemic sclerosis. Although the patients were different clinically, all complained of muscular weakness or poor exercise tolerance. The occurrence of muscle adenylate deaminase deficiency in both sexes suggests a possible autosomal mode of inheritance.

Heterogeneity of carnitine-palmitoyltransferase deficiency.

Episodes with muscle ache, rhabdomyolysis and myoglobinuria with or without associated renal insufficiency are characteristic of muscle carnitinepalmitoyltransferase (CPT) deficiency. However, patients differ from each other in many aspects, such as the kind of stimulus that triggers rhabdomyolysis, the ability to produce ketone bodies when fasting, whether the enzyme defect is localized in skeletal muscle or is general, and the nature of the enzyme defect, which may be in CPT I or CPT II or both. Studies of muscle, liver and fibroblasts from a patient with recurrent rhabdomyolysis spontaneously occurring or triggered by exercise or fever, revealed a CPT deficiency in the muscle and liver biopsy samples but normal CPT activity in cultured cells, differing from previously reported patients. The enzyme defect in muscle was evidenced by two different methods, but not when determined with a method that measures the formation of palmitoylcarnitine. The enzyme abnormality in the patient's liver was associated with a delayed ketone body production and with a dramatic increase in long-chain acylcarnitines in the serum when fasting. Moreover the patient was unable to build up ketones when fed long-chain triglycerides (LCT) but showed prompt ketogenic response when fed medium-chain triglycerides (MCT). The heterogeneity of clinical presentations and of the biochemical findings in patients with CPT deficiency are discussed.

Iodoacetate inhibition of glyceraldehyde-3-phosphate dehydrogenase as a model of human myophosphorylase deficiency (McArdle's disease) and phosphofructokinase deficiency (Tarui's disease).

A model of the human neuromuscular disorders myophosphorylase deficiency and phosphofructokinase deficiency has been developed using intra-aortic injection of sodium iodoacetate in adult male rats. Iodoacetate selectively inhibits in vivo the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase. The iodoacetate-injected rats develop electrically silent cramps in leg musculature during ischemic (or vigorous non-ischemic) exercise. Post-exercise rhabdomyolysis is evidenced by a 10-fold serum CPK elevation, excessive uptake of 99mTc-diphosphonate by cramped muscle, and type IIB fiber damage (histochemically-demonstrated) in cramped muscle. Further analysis of this model will allow a greater understanding of the clinical syndrome associated with the human disorders and permit development of successful treatment programs.

Cramps, muscle pain, and tubular aggregates.

A 31-year-old man had a nine-year history of exercise-induced cramps and muscle pain without myoglobinuria. Results of laboratory investigations differentiated his condition from the known disorders of carbohydrate and lipid metabolism. Light and electron microscopic examination of a muscle biopsy specimen showed tubular aggregates confined to type II fibers. Although the relationship of tubular aggregates to muscle cramps is uncertain, this association has been described previously and may be significant.

Myoadenylate deaminase deficiency--muscle biopsy and muscle culture in a patient with gout.

AMP deaminase activity was undetectable by a sensitive spectrophotometric assay in the muscle biopsy of a 37-year-old man with gout and exercise-related cramps and myalgia. Venous ammonia failed to rise after ischemic exercise, but the diagnostic value of this test is uncertain because changes of plasma ammonia after exercise varied greatly in different normal individuals. In the patient, AMP deaminase activity was normal not only in erythrocytes, leukocytes and cultured fibroblasts but also in muscle cultures. Presence of AMP deaminase in muscle cultures was probably due to the expression of a fetal isoenzyme under separate genetic control from adult muscle AMP deaminase.