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1/8. 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.
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2/8. Fatal infantile form of muscle phosphofructokinase deficiency.

    We studied a girl with an infantile syndrome of limb weakness, seizures, cortical blindness, and corneal opacifications; she died at age 7 months of respiratory failure. There was no consanguinity or family history of neuromuscular diseases. Histochemical and biochemical studies of muscle showed mildly increased glycogen content and markedly decreased PFK activity (1.4% of the normal mean). Anaerobic glycolysis in vitro confirmed the metabolic block. Immunofluorescence and immunotitration by ELISA using monoclonal antibodies against subunit M of PFK showed a normal amount of cross-reacting material. The brain showed typical features of neuroaxonal dystrophy. This variant of PFK deficiency may be due to a distinct genetic defect.
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3/8. A new variant case of muscle phosphofructokinase deficiency, coexisting with gastric ulcer, gouty arthritis, and increased hemolysis.

    Muscle phosphofructokinase (PFK) deficiency includes both clinically and genetically heterogeneous conditions. A 22-year-old man with muscle PFK deficiency due to previously unrecognized mutation was admitted because of gastric ulcer. He had noticed mild fatigability on vigorous exercise, but had never experienced painful cramps and myoglobinuria. His history included five time relapses of gastric ulcer and gouty arthritis at ages 19 and 21 years. His laboratory data showing impaired muscle glycolysis, increased hemolysis, and myogenic hyperuricemia had aspects in common with those reported for the classic form of this disease, except that lactate concentrations in his blood increased considerably after exercise. The mutant PFK enzyme of this patient, who was demonstrated to have a missense mutation, could exert some catalytic activity that permitted glycolytic flux in vivo, thus leading to the absence of typical myopathic symptoms. The association of relapsing gastric ulcer with muscle PFK deficiency was detected for the first time. There is a possibility that oxygen radical-induced tissue damage resulting from increased hypoxanthine on exertion plays a role in the pathogenesis of ulceration, since the patient is more tolerant to exercise than reported cases with the classic form of muscle PFK deficiency.
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4/8. Late-onset muscle weakness in partial phosphofructokinase deficiency: a unique myopathy with vacuoles, abnormal mitochondria, and absence of the common exon 5/intron 5 junction point mutation.

    Three patients (ages 51, 59, and 79) from two generations of an Ashkenazi Jewish family had partial (33% activity) phosphofructokinase (PFK) deficiency that presented with fixed muscle weakness after the age of 50 years. MR spectroscopy revealed accumulation of phosphomonoesters during exercise. Muscle biopsy showed a vacuolar myopathy with increased autophagic activity and several ragged-red and cytochrome c oxidase-negative fibers. The older patient, age 79 at biopsy, had several necrotic fibers. Electron microscopy revealed subsarcolemmal and intermyofibrillar glycogen accumulation and proliferation of mitochondria with paracrystalline inclusions, probably related to reduced availability of energy due to impaired glycolysis. The common point mutation of exon 5/intron 5 junction seen in Jewish Ashkenazi patients with PFK deficiency was excluded. We conclude that late-onset fixed muscle weakness occurs in partial PFK deficiency and it may represent the end result of continuing episodes of muscle fiber destruction. Partial enzyme deficiency in two successive generations suggests a unique molecular mechanism.
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5/8. Glycogenosis type VII (Tarui disease) in a Swedish family: two novel mutations in muscle phosphofructokinase gene (PFK-M) resulting in intron retentions.

    Phosphofructokinase (PFK) plays a major role in glycolysis. Human PFK is composed of three isoenzyme subunits (muscle [Ml, liver [L], and platelet [P]), which are encoded by different genes. Deficiency of muscle isoenzyme (PFK-M), glycogenosis type VII (Tarui disease), is an autosomal recessive disorder characterized by an exertional myopathy and hemolytic syndrome. Several disease-causing mutations have been identified in the PFK-M gene in Japanese, Ashkenazi Jewish, Italian, French Canadian, and Swiss patients. We describe the genetic defect in a Swedish family with affected individuals in two generations. The patients are compound heterozygotes: two different mutations result in retention of intron 13 or intron 16 sequences into mRNA. A G1127A transition destroys the 5' donor site of intron 13, resulting in a 155-nt retention of the intronic sequence. An a-to-g base change in intron 16 creates a new acceptor splice site, resulting in a 63-nt retention of intronic sequence. Both mutations are predicted to result in premature termination of translation. Some of the transcripts generated from the intron 16 mutated allele also contain intron 10 sequence unspliced.
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6/8. Partial block of glycolysis in late-onset phosphofructokinase deficiency myopathy.

    A late-onset, myopathic variant of phosphofructokinase (PFK) deficiency has been previously described in two patients of Ashkenazic descent. We report here on a non-Ashkenazic woman with the onset, at the age of 48 years, of a progressive limb girdle myopathy that was not preceded by a history of exercise intolerance. Muscle biopsy findings at the age of 58 years showed deposition of amylopectin-like material in muscle fibers and the absence of histochemical PFK activity. Enzymatic PFK activity in vitro was only 4% of normal. Since the forearm ischemic exercise test induced a sub-normal production of serum lactate, the patient underwent phosphorus magnetic resonance spectroscopy (31P-MRS), a non-invasive method that allows in vivo assessment of the functional status of the glycolytic pathway and mitochondrial oxidative metabolism by measuring the high-energy phosphates and cytosolic pH. In vivo, 31P-MRS disclosed a residual glycolytic flux and a normal rate of ATP production both at rest and during exercise. These results suggest that, in some patients, muscle PFK deficiency may be partial in vivo, and more severe in vitro, possibly due to protein or mRNA instability rather than absence. The presence of these findings in a patient with the late-onset myopathic form is compatible with a distinct pathogenetic mechanism, relying on progressive polysaccharide accumulation, rather than on acute energetic shortage in muscle fibers.
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7/8. Muscle phosphofructokinase deficiency in two generations.

    Phosphofructokinase (PFK) is the key regulatory enzyme of glycolysis. patients lacking the muscular isoform of PFK typically present with myopathy and compensated hemolysis (glycogenosis type VII or Tarui's disease). Since 1965 about 30 cases of muscular PFK deficiency have been reported. In most cases family history suggests a recessive inherited trait. We describe a family of Ashkenazi Jewish origin with two members in subsequent generations suffering from muscular PFK deficiency. The propositus, a 19-year-old male patient presented with weakness, myalgias and exercise intolerance since early infancy. His father also had early fatigue on exercise with myalgias; the mother and a 12-year-old brother were asymptomatic. Muscle biopsy of both the propositus and his father showed increased glycogen storage and absent histochemical stain for PFK. Biochemical studies of muscle revealed a markedly decreased PFK activity and dna analysis of the muscle PFK gene revealed compound heterozygosity in both cases. This is the first description of proven muscle PFK deficiency (glycogenosis type VII) in two subsequent generations.
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8/8. Impaired aerobic glycolysis in muscle phosphofructokinase deficiency results in biphasic post-exercise phosphocreatine recovery in 31P magnetic resonance spectroscopy.

    Using 31P magnetic resonance spectroscopy, energy metabolism in calf muscles of two patients with biochemically and genetically proven muscular phosphofructokinase deficiency, and an asymptomatic heterozygote was monitored during isometric foot plantarflexion performed under aerobic and anaerobic conditions and in the aerobic recovery phases. In the heterozygote only a moderate alteration from normal was found in terms of an elevated ATP demand during exercise. In the homozygote, hexose phosphates, indicated as phosphomonoesters, increased dramatically during contraction. Phosphomonoester accumulation resulted in consumption of free inorganic phosphate (P(i)). During ischemic exercise the absence of glycolytic ATP formation resulted in a linear time course of phosphocreatine breakdown and a moderate alkalinization. During the recovery, phosphocreatine resynthesis showed a biphasic time course, indicating that mitochondrial function itself was not directly affected. At first glance, the early depletion of P(i) below initial resting levels and the rate of phosphate splitting from sugar phosphates seemed to become the limiting factor for the rate of the oxidative phosphorylation and creatine kinase reaction. However, the actual concentrations of P(i) and ADP estimated at the onset of delay were too high to exclusively explain the dramatic delay in PCr resynthesis. For this reason, a reduced turnover of the citric acid cycle was assumed, which was caused by the complete absence of glycolysis in PFK deficiency patients. Furthermore, results from PFK deficiency patients were compared with previous findings from myophosphorylase deficiency patients in the literature.
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