My Diagnostic Odyssey-A Call to Expand Access to Genomic Testing for the Next Generation.

I attended the NSIGHT Ethics and Policy Advisory Board's meeting on sequencing newborns as a research associate in a joint apprenticeship between the University of California, San Francisco, Institute for Human Genetics and the university's Program in Bioethics. But I also came to the meeting with a deeply personal perspective: I had spent nearly my entire childhood in search of a diagnosis and therefore was eager to hear the board's discussion on how to ethically include genomic sequencing early in life. Genomic sequencing in the newborn period could have helped me avoid my diagnostic odyssey by revealing the cause of my condition shortly after birth.

Metabolic Myopathies.

PURPOSE OF REVIEW: Metabolic myopathies are genetic disorders that impair intermediary metabolism in skeletal muscle. Impairments in glycolysis/glycogenolysis (glycogen-storage disease), fatty acid transport and oxidation (fatty acid oxidation defects), and the mitochondrial respiratory chain (mitochondrial myopathies) represent the majority of known defects. The purpose of this review is to develop a diagnostic and treatment algorithm for the metabolic myopathies. RECENT FINDINGS: The metabolic myopathies can present in the neonatal and infant period as part of more systemic involvement with hypotonia, hypoglycemia, and encephalopathy; however, most cases present in childhood or in adulthood with exercise intolerance (often with rhabdomyolysis) and weakness. The glycogen-storage diseases present during brief bouts of high-intensity exercise, whereas fatty acid oxidation defects and mitochondrial myopathies present during a long-duration/low-intensity endurance-type activity or during fasting or another metabolically stressful event (eg, surgery, fever). The clinical examination is often normal between acute events, and evaluation involves exercise testing, blood testing (creatine kinase, acylcarnitine profile, lactate, amino acids), urine organic acids (ketones, dicarboxylic acids, 3-methylglutaconic acid), muscle biopsy (histology, ultrastructure, enzyme testing), MRI/spectroscopy, and targeted or untargeted genetic testing. SUMMARY: Accurate and early identification of metabolic myopathies can lead to therapeutic interventions with lifestyle and nutritional modification, cofactor treatment, and rapid treatment of rhabdomyolysis.

Infantile form of muscle phosphofructokinase deficiency in a premature neonate.

Muscle phosphofructokinase (PFK) deficiency is a rare autosomal recessive disease. We report the case of a preterm female infant who was diagnosed with the infantile form of phosphofructokinase deficiency due to a lack of PFK activity in her muscles, manifesting at a corrected age of 1 month as floppy infant syndrome, congenital joint contracture, cleft palate and duplication of the pelvicalyceal system. She died at a corrected age of 6 months due to respiratory failure. We further reviewed other infantile cases in the literature. Congenital hypotonia (78.6%), arthrogryposis (64.3%) and other systemic involvement including encephalopathy (35.7%) and cardiomyopathy (21.4%) are common presentations of the infantile form of PFK deficiency. The overall survival rate of the infantile form is low. The early recognition of multiple system involvement is essential to provide better clinical care for infants with the infantile form of PFK deficiency.

[Exercise-induced muscle pain due to phosphofrutokinase deficiency: Diagnostic contribution of metabolic explorations (exercise tests, 31P-nuclear magnetic resonance spectroscopy)]. / Intolérance musculaire à l'effort par déficit en phosphofructokinase : apport au diagnostic du bilan métabolique musculaire (tests d'effort, spectroscopie RMN du P31).

INTRODUCTION: Muscle phosphofructokinase deficiency, the seventh member of the glycogen storage diseases family, is also called Tarui's disease (GSD VII). METHODS: We studied two patients in two unrelated families with Tarui's disease, analyzing clinical features, CK level, EMG, muscle biopsy findings and molecular genetics features. Metabolic muscle explorations (forearm ischemic exercise test [FIET]; bicycle ergometer exercise test [EE]; 31P-nuclear magnetic resonance spectroscopy of calf muscle [31P-NMR-S]) are performed as appropriate. RESULTS: Two patients, a 47-year-old man and a 38-year-old woman, complained of exercise-induced fatigue since childhood. The neurological examination was normal or showed light weakness. Laboratory studies showed increased CPK, serum uric acid and reticulocyte count without anemia. There was no increase in the blood lactate level during the FIET or the EE although there was a light increase in the respiratory exchange ratio during the EE. 31P-NMR-S revealed no intracellular acidification or accumulated intermediates such as phosphorylated monoesters (PME) known to be pathognomic for GSD VII. Two new mutations were identified. DISCUSSION: FIET and EE were non-contributive to diagnosis, but 31P-NMR provided a characteristic spectra of Tarui's disease, in agreement with phosphofructokinase activity level in erythrocytes. Muscle biopsy does not always provide useful information for diagnosis. In these two cases, genetic studies failed to establish a genotype-phenotype correlation. CONCLUSION: The search for phosphofructokinase deficiency should be continued throughout life in adults experiencing fatigability or weakness because of the severe disability for daily life activities caused by the late onset form.

Missense mutation in PFKM associated with muscle-type phosphofructokinase deficiency in the Wachtelhund dog.

Hereditary muscle-type phosphofructokinase (PFK) deficiency causing intermittent hemolytic anemia and exertional myopathy due to a single nonsense mutation in PFKM has been previously described in English Springer and American Cocker Spaniels, Whippets, and mixed breed dogs. We report here on a new missense mutation associated with PFK deficiency in Wachtelhunds. Coding regions of the PFKM gene were amplified from genomic DNA and/or cDNA reverse-transcribed from RNA of EDTA blood of PFK-deficient and clinically healthy Wachtelhunds and control dogs. The amplicons were sequenced and compared to the published canine PFKM sequence. A point mutation (c.550C>T, in the coding sequence of PFKM expressed in blood) was found in all 4 affected Wachtelhunds. This missense mutation results in an amino acid substitution of arginine (Arg) to tryptophan (Trp) at position 184 of the protein expressed in blood (p.Arg184Trp). The mutation is located within an alpha-helix, and based on the SIFT analysis, this amino acid substitution is not tolerated. Amplifying the region around this mutation and digesting the PCR fragment with the restriction enzyme MspI, produces fragments that readily differentiate between PFK-deficient, carrier, and normal animals. Furthermore, we document 2 additional upstream PFKM exons expressed in canine testis but not in blood. Despite their similar phenotypic appearance and use for hunting, Wachtelhunds and English Springer Spaniels are not thought to have common ancestors. Thus, it is not surprising that different mutations are responsible for PFK deficiency in these breeds. Knowledge of the molecular basis of PFK deficiency in Wachtelhunds provides an opportunity to screen and control the spread of this deleterious trait.

Juvenile-onset permanent weakness in muscle phosphofructokinase deficiency.

We describe a 41-year-old Moroccan woman with phosphofructokinase (PFK) deficiency who presented slowly progressive muscular weakness since childhood, without rhabdomyolysis episode or hemolytic anemia. Deltoid biopsy revealed massive glycogen storage in the majority of muscle fibers and polysaccharide deposits. PFK activity in muscle was totally absent. A novel homozygous non-sense mutation was detected in PFKM gene. Our observation suggests that juvenile-onset fixed muscle weakness may be a predominant clinical feature of PFK deficiency. Vacuolar myopathy with polyglucosan deposits remains an important morphological hallmark of this rare muscle glycogenosis.

Clinical features and new molecular findings in muscle phosphofructokinase deficiency (GSD type VII).

Muscle phosphofructokinase (PFKM) deficiency, a rare disorder of glycogen metabolism also known as glycogen storage disease type VII (GSDVII), is characterized by exercise intolerance, myalgias, cramps and episodic myoglobinuria associated with compensated hemolytic anaemia and hyperuricemia. We studied five patients with PFKM deficiency coming from different Italian regions. All probands showed exercise intolerance, hyperCKemia, cramps and myoglobinuria. One patient had a mild hypertrophic cardiomyopathy. Biochemical studies revealed residual PFK activity ranging from 1 to 5%. Molecular genetic analysis identified four novel mutations in the PFKM gene. In our series of patients, clinical and laboratory features were similar in all but one patient, who had an unusual phenotype characterized by 25 ears disease history, high CK levels, hypertrophic cardiomyopathy with paroxysmal atrial fibrillation without fixed muscle weakness.

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.

Tarui disease and distal glycogenoses: clinical and genetic update.

Phosphofructokinase deficiency (Tarui disease) was the first disorder recognized to directly affect glycolysis. Since the discovery of the disease, in 1965, a wide range of biochemical, physiological and molecular studies have greatly contributed to our knowledge concerning not only phosphofructokinase function in normal muscle but also on the general control of glycolysis and glycogen metabolism. Studies on phosphofructokinase deficiency vastly enriched the field of glycogen storage diseases, making a relevant improvement also in the molecular genetic area. So far, more than one hundred patients have been described with prominent clinical symptoms characterized by muscle cramps, exercise intolerance, rhabdomyolysis and myoglobinuria, often associated with haemolytic anaemia and hyperuricaemia. The muscle phosphofructokinase gene is located on chromosome 12 and about 20 mutations have been described. Other glycogenoses have been recognised in the distal part of the glycolytic pathway: these are infrequent but some may induce muscle cramps, exercise intolerance and rhabdomyolysis. Phosphoglycerate Kinase, Phosphoglycerate Mutase, Lactate Dehydrogenase, beta-Enolase and Aldolase A deficiencies have been described as distal glycogenoses. From the molecular point of view, the majority of these enzyme deficiencies are sustained by "private" mutations.

Acute renal failure in a patient with phosphofructokinase deficiency.

A 16-year-old Caucasian girl was admitted to hospital with acute renal failure and hemolytic anemia due to rhabdomyolysis following a 3-km walk. (31)P-magnetic resonance spectroscopy provided characteristic spectra of type VII glycogen storage disease (phosphofructokinase deficiency).

Phosphofructokinase deficiency; past, present and future.

Phosphofructokinase deficiency (Tarui disease, glycogen storage disease VII, GSD VII) stands out among all the GSDs. PFK deficiency was the first recognized disorder that directly affects glycolysis. Ever since the discovery of the disease in 1965, a wide range of biochemical, physiological and molecular studies of the disorder have greatly expanded our understanding of the function of normal muscle, general control of glycolysis and glycogen metabolism. The studies of PFK deficiency vastly enriched the field of glycogen storage diseases, as well as the field of metabolic and neuromuscular disorders. This article cites a historical overview of this clinical entity and the progress that has been made in molecular genetic area. We will also present the results of a search in-silico, which allowed us to identify a previously unknown sequence of the human platelet PFK gene (PFK-P). In addition, we will describe phylogenetic analysis of evolution of PFK genes.

Alpha-sarcoglycanopathy previously misdiagnosed as Duchenne muscular dystrophy: implications for current diagnostics and patient care.

Differential diagnosis of limb-girdle muscular dystrophy, including alpha-sarcoglycanopathy and Duchenne muscular dystrophy, is impossible to acheive on clinical grounds alone; therefore immunohistology, Western blotting and molecular genetic analysis are manadatory for a correct diagnosis. The patient's genotype with a hitherto unknown mutation (Tyr134STOP) in exon 5 adds to the growing spectrum of mutations in the alpha-sarcoglycan gene.

Haemolytic anaemia and exercise intolerance due to phosphofructokinase deficiency in related springer spaniels.

Phosphofructokinase (PFK) deficiency is an autosomal recessive inherited disorder in dogs causing haemolytic crises and exertional myopathy. The clinical signs may be confused with those of recurrent immune-mediated haemolytic anaemia. The deficiency has been commonly observed in field trial (working) English springer spaniels (ESSPs), but also in the conformation line of ESSPs in the USA over the past two decades. This report documents the first family of ESSPs found with PFK deficiency in Europe. Two related adult ESSPs in Denmark had intermittent signs of pigmenturia after exercise (hunting) and had evidence of a regenerative haemolytic anaemia. Based upon DNA sequencing data, both dogs had the previously described nonsense point mutation in the muscle-type PFK gene (delta2228G-->A). Study of 17 related family members using a simple and accurate PFK-DNA test revealed one additional PFK-deficient dog (with minor exercise intolerance), nine carriers and seven normal (or 'clear') ESSPs. Recently, the authors have also identified PFK carriers and affected ESSPs in the UK. Screening for PFK deficiency is recommended for ESSPs with suspicious clinical signs and before using any for field trials or breeding in order to prevent the further spread of this hereditary disorder.

Phosphoglycerate kinase deficiency in two brothers with McArdle-like clinical symptoms.

Phosphoglycerate kinase (PGK) catalyses the transfer of the acylphosphate group of 1,3-diphosphoglycerate to ADP with formation of 3-phosphoglycerate and ATP in the terminal stage of the glycolytic pathway. Two young brothers are presented who both experienced muscle pain, cramps and stiffness shortly after beginning heavy exercise. After these episodes they noticed that the urine was dark brown, indicating rhabdomyolysis and myoglobinuria. The neurological examinations were without remarks. There was no lactate increase in the ischaemic forearm exercise test. Both had very low PGK levels in muscle, erythrocytes, leukocytes and fibroblasts. This is the first family with more than one affected case of PGK deficiency and exercise-induced stiffness, myalgia and rhabdomyolysis. The clinical manifestations may resemble myophosphorylase deficiency (McArdle's disease: glycogenosis Type V) and muscle phosphofructokinase deficiency (Tarui's disease: glycogenosis Type VII). PGK deficiency is inherited as an X-linked trait and may show other features such as mental retardation and/or haemolytic anaemia.

Muscle phosphofructokinase deficiency (Tarui's disease): report of a case.

A 14-year-old girl had an acute episode of rhabdomyolysis after vigorous exercise and seizures. Laboratory studies revealed elevated creatine phosphokinase (CPK) activity and myoglobinuria without acute renal failure, as well as mild indirect hyperbilirubinemia, and hyperuricemia. The elevated CPK activity, mild indirect hyperbilirubinemia, and hyperuricemia persisted during a 10-month follow-up period, during which chronic hemolysis without overt anemia was also noted. A muscle biopsy specimen from the left biceps muscle revealed occasional muscle fiber necrosis and mild excess of glycogen accumulation on periodic acid-Schiff staining. Histochemical reactions were negative with phosphofructokinase (PFK) stain when fructose-6-phosphate was used as the substrate, but positive when fructose 1,6-bisphosphate was used as the substrate. These findings confirmed the diagnosis of muscle PFK deficiency (Tarui's disease), which is a defect of glycolysis in muscles and erythrocytes. Less than 40 such patients have been reported to date. When a specific metabolic myopathy is suspected in children with rhabdomyolysis, symptoms of hemolysis should also be sought to identify Tarui's disease. To the best of our knowledge, this is the first case of Tarui's disease identified in Taiwan.