Angina for 14 years

Phosphofructokinase deficiency and portal and mesenteric vein thrombosis

Phosphofructokinase deficiency is a rare disorder with less than 100 reported cases; the contribution of altered glucose metabolism in other tissues to the pathogenesis of the disease is not fully understood. The authors present a unique case of portal and mesenteric vein thrombosis in a 43-year-old man with a known case of phosphofructokinase deficiency.

Phosphofructo-1-kinase deficiency leads to a severe cardiac and hematological disorder in addition to skeletal muscle glycogenosis

Mutations in the gene for muscle phosphofructo-1-kinase (PFKM), a key regulatory enzyme of glycolysis, cause Type VII glycogen storage disease (GSDVII). Clinical manifestations of the disease span from the severe infantile form, leading to death during childhood, to the classical form, which presents mainly with exercise intolerance. PFKM deficiency is considered as a skeletal muscle glycogenosis, but the relative contribution of altered glucose metabolism in other tissues to the pathogenesis of the disease is not fully understood. To elucidate this issue, we have generated mice deficient for PFKM (Pfkm^−/−). Here, we show that Pfkm^−/− mice had high lethality around weaning and reduced lifespan, because of the metabolic alterations. In skeletal muscle, including respiratory muscles, the lack of PFK activity blocked glycolysis and resulted in considerable glycogen storage and low ATP content. Although erythrocytes of Pfkm^−/− mice preserved 50% of PFK activity, they showed strong reduction of 2,3-biphosphoglycerate concentrations and hemolysis, which was associated with compensatory reticulocytosis and splenomegaly. As a consequence of these haematological alterations, and of reduced PFK activity in the heart, Pfkm^−/− mice developed cardiac hypertrophy with age. Taken together, these alterations resulted in muscle hypoxia and hypervascularization, impaired oxidative metabolism, fiber necrosis, and exercise intolerance. These results indicate that, in GSDVII, marked alterations in muscle bioenergetics and erythrocyte metabolism interact to produce a complex systemic disorder. Therefore, GSDVII is not simply a muscle glycogenosis, and Pfkm^−/− mice constitute a unique model of GSDVII which may be useful for the design and assessment of new therapies.

Type VII glycogen storage disease (GSDVII), or Tarui disease, is a rare genetic disorder characterized by glycogen accumulation in skeletal muscle. The molecular cause is loss of activity of the muscle isoform of phosphofructokinase (PFK), which phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate, commiting glucose to glycolysis. Entry of fructose-6-phosphate into glycolysis is thus blocked, increasing glycogen synthesis and accumulation. Clinical manifestations of the disease are heterogeneous, ranging from exercise intolerance to early childhood death. To further understand the human pathology, we generated mice lacking muscle PFK. As in human patients, these mice showed severe exercise intolerance, hemolysis, and most died young. Lack of glycolysis in skeletal muscle also causes alterations in bioenergetics and compensatory changes in key metabolic genes. Additionally, although erythrocytes retained 50% of normal PFK activity, their overall functionality was impaired, aggravating the muscle dysfunction. Moreover, marked metabolic alterations in the heart lead to chronic hypertrophy, suggesting that cardiac pathology in GSDVII may be underestimated or misdiagnosed. This study indicates that this disease is more complex than a muscle glycogenosis and that symptoms other than those classically described should be taken into consideration. Finally, this animal model will enable us to develop new therapeutic approaches and better diagnostic tools.

Possible causes of symptoms in suspected coronary heart disease but normal angiograms

BACKGROUND

In patients with suspected coronary heart disease and normal angiography, the causes of cardiac symptoms frequently remain undetermined. A correct diagnosis is desirable, however, since some of the underlying disorders may be curable, treatable, influence prognosis, or induce screening of the relatives.

HYPOTHESIS

In such patients, the prevalence of arterial hypertension, hemochromatosis, hypothyroidism, hypoparathyroidism, tachycardiomyopathy, amyloidosis, and neuromuscular disorders as a possible cause for their symptoms and the seroprevalence of micro-organisms, known to cause myocardial damage, were assessed.

METHODS

Consecutive patients with normal coronary angiograms were invited for two visits comprising clinical history and investigation, electrocardiograms, blood tests, and echocardiography. Patients were investigated neurologically if unexplained anginal chest pain or creatine kinase elevation persisted or if echocardiography showed isolated left ventricular abnormal trabeculations.

RESULTS

In 71 patients (31 women, 40 men, mean age 60 years), the most common cause for cardiac symptoms was hypertension (66%), followed by neuromuscular disorders (13%), tachycardiomyopathy (9%), hypothyroidism (4%), and hemochromatosis (3%). The seroprevalence for Chlamydia species was 90%, Helicobacter pylori 70%, Chlamydia pneumoniae 63%, Borrelia burgdorferi sensu lato 15%, and Rickettsia conorii 10%. No possible cause was found in 24% of the patients.

CONCLUSIONS

In patients with suspected coronary heart disease and normal angiograms, hypertension, neuromuscular disorders, tachycardiomyopathy, hypothyroidism, and hemochromatosis should be considered as possible causes.

Primary myopathies and the heart

Myopathies are frequently not confined to the skeletal muscles but also involve other organs or tissues. One of the most frequently affected organ in addition to the skeletal muscle is the heart (cardiac involvement, CI). CI manifests as impulse generation or conduction defects, focal or diffuse myocardial thickening, dilation of the cardiac cavities, relaxation abnormality, hypertrophic, dilated, restrictive cardiomyopathy, apical form of hypertrophic cardiomyopathy, noncompaction, Takotsubo phenomenon, secondary valve insufficiency, intra-cardiac thrombus formation, or heart failure with systolic or diastolic dysfunction. CI occurs in dystrophinopathies, Emery-Dreifuss muscular dystrophy, facioscapulohumeral muscular dystrophy, limb girdle muscular dystrophies, laminopathies, congenital muscular dystrophies, myotonic dystrophies, congenital myopathies, metabolic myopathies, desminopathies, myofibrillar myopathy, Barth syndrome, McLeod syndrome, Senger's syndrome, and Bethlem myopathy. Patients with myopathy should be cardiologically investigated as soon as their neurological diagnosis is established, since supportive cardiac therapy is available, which markedly influences prognosis and outcome of CI in these patients.

Serum creatine kinase elevation in a medical department

Serum creatine kinase (CK) levels are diagnostic markers for acute myocardial infarction. Many other causes however, including neuromuscular disorders, may induce serum CK elevation as well. Aim of the study was to investigate the prevalence of potential causes for serum CK elevation in a medical department. In particular we were interested in the recognition of patients in whom serum CK elevation was due to a neuromuscular disorder. Included in this prospective study were 100 consecutive patients in whom the CK level, determined at admission, was increased (> 70 IU/l in female, > 80 IU/l in male patients). After admission we looked for the presence of causes known to induce CK elevation. Patients with no potential cause for CK elevation were invited for follow-up investigations three months later. If no potential cause could be found and if CK was elevated again on this occasion, the patient was referred for a comprehensive neurological investigation. The prevalence of patients with CK elevation was 11.2%. The 100 patients (44 female, 56 male) were aged from 23 to 94 (mean 67) years. In 95% CK elevation was only up to 500 IU/l. The most frequent cause for serum CK elevation was acute myocardial infarction in 32%. Further frequent causes were drug intake (32%), fall (24%), haematoma (17%), intramuscular injection (16%) and malignancy (11%). In 61% of the cases at least two potential causes for serum CK elevation could be detected. Neuromuscular disorders were found in only 2%. This study shows that serum CK elevation occurs in 11% of patients admitted to a medical department and can be explained by acute myocardial infarction in only 32%. In almost two thirds of the patients, more than one potential cause for serum CK elevation can be found thus making CK elevation a rather unspecific finding. Neuromuscular disorders are rarely found as a cause of serum CK elevation in a medical department.

Cardiac involvement in primary myopathies

Simultaneous or temporarily staggered affection of both the skeletal as well as the cardiac muscle (cardiac involvement, CI) is a frequent finding in primary myopathies (MPs). CI leads to impulse generation defects, impulse conduction defects, thickened myocardium, left ventriculalr hypertrabeculation, dilatation of the cardiac cavities, secondary valve insufficiency, reduction of coronary vasodilative reserve, intracardial thrombus formation, and heart failure with systolic and diastolic dysfunction. CI has been found in Duchenne muscular dystrophy (MD), Becker MD, Emery-Dreifuss MD, facioscapulohumeral MD, sarcoglycanopathies, myotubular congenital MD, myotonic dystrophies type 1 and 2, proximal myotonic myopathy, myoadenylate deaminase deficiency, glycogenosis type II, III, IV, VII and IX, carnitine deficiency, mitochondriopathy, desmin MP, nemaline MP, central core disease, multicore MP, congenital fiber-type disproportion MP, Barth syndrome, McLeod syndrome and Bethlem MP. Patients with any of the above-mentioned myopathies should be cardiologically investigated as soon as their diagnosis is established, since sufficient cardiac therapy improves CI in MPs and since management of these patients is influenced by the degree of CI.

Chest pain in cardiac syndrome X--caused by neuromuscular disorders?

We wanted to find out if chest pain in cardiac syndrome X can be a manifestation of neuromuscular disorders. Five patients with cardiac syndrome X (3 women, 2 men), aged 34 to 70 years, consented with a clinical neurological examination, muscle enzyme testing, electroneurography of the right median and peroneal nerves and electromyography of the right brachial biceps and anterior tibial muscles. A neuromuscular disorder was found in 1 of the 5 investigated patients. The 60-year-old man presented with a monoparesis of the left leg and sensory dysfunction of the left upper and lower limb. He was diagnosed as having either posttraumatic myelopathy or radiculopathy. Since chest pain in cardiac syndrome X can be caused by neuromuscular disorders, a comprehensive neurological examination is recommended in patients with this disorder.