Chronic myopathy with a partial deficiency of the carnitine palmityltransferase enzyme

To date, chronic myopathy has not been reported (to our knowledge) to occur in carnitine palmityltransferase (CPT) deficiency, a disorder of muscle lipid metabolism. We describe two patients with CPT deficiency: a mother, who had a partial CPT deficiency associated with fixed proximal weakness but without rhabdomyolysis, and her son, who had a complete CPT deficiency (95% reduction in enzyme activity) and who suffered from classic attacks of exercise-induced rhabdomyolysis but had normal strength on recovery. Careful examination of family members of patients with complete CPT deficiency is suggested in order to identify clinically affected heterozygotes.     

Valproic acid triggers acute rhabdomyolysis in a patient with carnitine palmitoyltransferase type II deficiency

A 47-year-old man suffering from a bipolar disorder and intermittent myoglobinuria presented with acute rhabdomyolysis with renal failure after starting therapy with valproic acid. On morphological examination, skeletal muscle revealed increased lipid storage. Biochemically, decreased enzyme activity of carnitine palmitoyltransferase (CPT) type II with carnitine levels in the lower limit was found. Genetic analysis detected the common Ser113Leu substitution on one allele of the CPT2 gene. We conclude that valproic acid should be avoided in patients with CPT type II deficiency.     

No carnitine palmitoyltransferase deficiency in skeletal muscle in 18 malignant hyperthermia susceptible individuals

Malignant hyperthermia is a rare, potentially life threatening pharmacogenetic disorder triggered by volatile anaesthetics and depolarizing muscle relaxants. The clinical picture comprises rhabdomyolysis, metabolic and respiratory acidosis, and hyperthermia. Carnitine palmitoyltransferase II deficiency is a metabolic myopathy affecting the transport of fatty acids into the mitochondria, leading to impaired energy supply under stressful conditions resulting in muscle weakness and rhabdomyolysis. It was postulated in a previous study that some patients with the MH phenotype have a carnitine palmitoyltransferase deficiency. To investigate a potential association, we tested 18 individuals with proven MH susceptibility for impairment of carnitine palmitoyltransferase enzyme activity in muscle. Enzyme activity was normal in all individuals tested indicating no impairment of the CPT system in this sample of malignant hyperthermia susceptible individuals. Thus our data do not support the hypothesis that susceptibility to malignant hyperthermia has an effect on the carnitine palmitoyltransferase enzyme system.     

Therapeutic options in other metabolic myopathies

Adult patients with metabolic myopathies typically present with exercise-induced pain, cramps, fatigue, and myoglobinuria. The current therapeutic options of glycogen and lipid storage myopathies include dietary treatments, excersise training, and pharmacological supplementations. Herein is a review of evidence from randomized controlled trials in McArdle disease (glycogen storage disease type V, muscle phosphorylase deficiency) and carnitine palmitoyltransferase (CPT) 2 deficiency. A brief overview on current treatment options in rhabdomyolysis is also included because patients with McArdle disease and CPT 2 often experience such potentially life-threatening complications.     

Importance of acylcarnitine profile analysis for disorders of lipid metabolism in adolescent patients with recurrent rhabdomyolysis: Report of two cases

Metabolic myopathies due to disorders of lipid metabolism are a heterogeneous group of diseases. Newborns may present with hypotonia and convulsions, while progressive proximal muscle weakness or recurrent episodes of muscle weakness accompanied by rhabdomyolysis/myoglobinuria may be seen in older ages. There is little knowledge on detection of disorders of lipid metabolism by acylcarnitine profile (ACP) analysis by tandem mass spectrometry outside the neonatal period particularly in cases with recurrent rhabdomyolysis first presenting in adolescence and adulthood. Two adolescent female cases presented with episodes of rhabdomyolysis and muscle weakness. A 13-year-old patient had five episodes of rhabdomyolysis triggered by infections. Tandem mass spectrometry was normal. A 16-year-old female patient was hospitalized eight times due to recurrent rhabdomyolysis. Increased levels of C14:2, C14:1, and C14 were determined in tandem mass spectrometry. Final diagnoses were carnitine palmitoyltransferase II (CPT II) deficiency and very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. Increased serum levels of long-chain acylcarnitine can guide to the diagnosis of lipid metabolism disorders. Serum ACP should be performed before enzyme assay and genetic studies.     

Metabolic causes of recurrent rhabdomyolysis

Objectives– The aim of the study was to evaluate the biochemical causes of recurrent rhabdomyolysis in Finland. Material and methods– We examined 22 patients with recurrent rhabdomyolysis, and 26 patients with one episode of rhabdomyolysis or other symptoms compatible with metabolic myopathy. Muscle histopathology and activities of phosphorylase (PHRL) (total and active), phosphofructokinase (PFK), carnitine palmitoyltransferase (CPT) and myoadenylate deaminase (MAD) were studied. The limit of enzyme deficiency was defined as enzyme activity less than 5% of the mean of the control subjects. Results– We found 4 patients with muscle PHRL deficiency, 1 patient with PFK deficiency and 1 patient with evidence of phosphorylase kinase deficiency. One patient had Becker's muscle dystrophy, 2 patients had unspecified dystrophies, 1 patient had Miyoshi myopathy, and 1 patient had a form of mitochondrial encephalomyopathy (MELAS). Conclusion– Enzyme defects were found in 23% of the patients with recurrent rhabdomyolysis. Other muscle diseases, muscular dystrophies or myopathies, were detected in 18% of these patients, emphasizing the value of clinical and histopathological examination of patients with previous rhabdomyolysis.     

Rhabdomyolysis and acute encephalopathy in late onset medium chain acyl-CoA dehydrogenase deficiency.

A previously asymptomatic 30 year old man presented with rhabdomyolysis, muscle weakness, and acute encephalopathy after strenuous exertion in the cold without adequate food intake. Serum and muscle carnitine concentrations were decreased. Urinary excretion of carnitine and glycine esters and biochemical examination of skeletal muscle and fibroblasts led to the diagnosis of medium chain acyl-CoA dehydrogenase (MCAD) deficiency. A point mutation at nucleotide position 985 of the coding region of the MCAD gene was found. The MCAD protein was synthesised in the patient's fibroblasts at a normal rate, but was unstable. In general, patients in whom the 985 point mutation has been established show much more severe clinical symptoms and other symptoms than those seen in this patient. The relation of the 985 point mutation and the residual MACD activity to the symptoms is not as straightforward as previously thought.     

Miopatia w przebiegu niedoboru palmitylotransferazy karnityny II

Congenital deficiency of carnitine palmitoyltransferase (CPT) II is a disease with an autosomal recessive inheritance of phenotypic variability which depends on age at the onset of symptoms. Three entities associated with deficiency of CPT II are known: the perinatal, the infantile and the adult form. The perinatal disease is the most severe form and is invariably fatal. On the other hand, the adult CPT II clinical phenotype is benign and requires additional external triggers such as high-intensity exercise to provoke myopathic symptoms. We report a case of adult CPT II deficiency presenting with the subtle symptoms of myopathy.A 32-year-old man was admitted to the hospital complaining of muscle pain after exercise. Athletic appearance drew attention, because the patient denied practicing sport. Neurological examination revealed marked tiredness during the single-leg hop test without other abnormalities.Electromyography (EMG) and serum biochemistry were not typical for myopathy. Routine histopathological examination did not reveal any abnormalities of structure of muscle fibers. Diagnosis was established after ultrastructural and biochemical analysis which revealed changes typical for CPT II deficiency.     

Lipid storage myopathies

Summary Various cases of lipid storage myopathies have been described. The biochemical defect could be determined in only some of these cases. The syndromes identified to date are as follows: carnitine deficiency (type I lipid storage myopathy), carnitine-palmityltransferase (CPT) deficiency and pyruvate-decarboxylase deficiency. In the last two diseases the vacuolization in muscle is not marked.The case of a 10 year old carnitine deficient patient with a history of insidious muscle weakness in the proximal limb and neck muscles is presented. The patient was treated with oral carnitine and a medium chain triglyceride diet for 18 months and her clinical status has remained improved. In other lipid storage patients prednisone treatment resulted in improvement.In cases of suspected lipid storage myopathy the following studies are indicated: 1) examination of ketone bodies in serum and urine during fasting, long chain and medium chain triglyceride diets; 2) serum triglyceride and serum carnitine; 3) study on fresh muscle and fibroblasts with labeled substrates, biochemical determination of carnitine and CPT in muscle.This paper was presented at the meeting of the Swiss Neurological Society and the Swiss Society of Muscular Disease in November 1975, Zürich, Switzerland     

Familial carnitine deficiency: further evidence for autosomal recessive transmission with variable expression.

Carnitine deficiency occurring in families has been rarely reported and the genetic transmission has not yet been clearly elucidated. Five members of one family showing marked heterogeneity of carnitine deficiency states are presented. In three patients, there was no correlation between measurable carnitine levels in serum and muscle and the clinical findings. The parents, who are remote relatives from an isolated village in Kurdistan (Iraq), had low muscle carnitine levels; however, they were asymptomatic. One son, with systemic carnitine deficiency causing muscle weakness and recurrent episodes of severe hepatic encephalopathy, died at 3 years of age. His brother had mild proximal muscle weakness associated with low muscle carnitine levels. He was successfully treated with L-carnitine and prednisone. A daughter is asymptomatic, but with low serum and muscle levels of carnitine. The marked heterogeneity of carnitine deficiency states within one family, where both parents had low muscle carnitine levels, suggests an autosomal recessive inheritance with variable expression.     

Normal muscle CPT1 and CPT2 activities in hepatic presentation patients with CPT1 deficiency in fibroblasts. Tissue specific isoforms of CPT1?

Human carnitine palmitoyltransferase (CPT) deficiency results in 2 clinical forms: a more common "muscular form" with myoglobinuria with or without delayed or impaired ketogenesis and a rare "hepatic form" with hypoketotic hypoglycemia, encephalopathy and seizures without muscular manifestations. We present 2 patients, a male (patient 1) and a female (patient 2) with infantile "hepatic" CPT deficiency and previously documented CPT1 deficiency in fibroblasts. In patient 2, a deficiency of "total" CPT activity in liver had also been previously documented. We set up an isotope exchange assay system that effectively differentiated CPT1 and CPT2 activities in muscle. We found normal CPT1 and CPT2 activities in our patients under near saturating substrate conditions. The CPT1 and CPT2 activities were suppressed to a strikingly similar degree under different kinetic conditions as compared to control muscle and were found to have similar Km values for carnitine and PCoA. With Km concentrations of carnitine, the mean residual activities of CPT1 for patients 1 and 2 were 49 and 44%, respectively (control range 40-53%); the mean residual activities of CPT2 were 60 and 46%, respectively (control range 49-59%). With Km concentrations of PCoA, the mean residual activities of CPT1 for patients 1 and 2 were 52 and 58%, respectively (control range of 52-59%); mean residual activities of CPT2 were 54% and 56%, respectively (control range of 51-68%). When the Vmax concentration of PCoA was doubled and bovine serum albumin reduced to 0.1%, the mean residual activities of CPT1 for patients 1 and 2 were 69 and 63%, respectively (control range 60-80%). In "muscular" patients, a marked absolute deficiency of CPT2 activity (less than 12% residual) was found with an apparent increased sensitivity to suppression of enzymatic activity when the Km concentration of carnitine was used. We suggest that CPT1 and CPT2 may be separate proteins. Furthermore, CPT1 itself may exist as tissue-specific isoforms being the same protein in liver and fibroblasts and a different protein in muscle. Either could be encoded for by the same or closely related genes.     

Disorders of muscle lipid metabolism: Diagnostic and therapeutic challenges

Disorders of muscle lipid metabolism may involve intramyocellular triglyceride degradation, carnitine uptake, long-chain fatty acids mitochondrial transport, or fatty acid β-oxidation. Three main diseases leading to permanent muscle weakness are associated with severe increased muscle lipid content (lipid storage myopathies): primary carnitine deficiency, neutral lipid storage disease and multiple acyl-CoA dehydrogenase deficiency. A moderate lipidosis may be observed in fatty acid oxidation disorders revealed by rhabdomyolysis episodes such as carnitine palmitoyl transferase II, very-long-chain acyl-CoA dehydrogenase, mitochondrial trifunctional protein deficiencies, and in recently described phosphatidic acid phosphatase deficiency. Respiratory chain disorders and congenital myasthenic syndromes may also be misdiagnosed as fatty acid oxidation disorders due to the presence of secondary muscle lipidosis. The main biochemical tests giving clues for the diagnosis of these various disorders are measurements of blood carnitine and acylcarnitines, urinary organic acid profile, and search for intracytoplasmic lipid on peripheral blood smear (Jordan’s anomaly). Genetic analysis orientated by the results of biochemical investigation allows establishing a firm diagnosis. Primary carnitine deficiency and multiple acyl-CoA dehydrogenase deficiency may be treated after supplementation with carnitine, riboflavine and coenzyme Q10. New therapeutic approaches for fatty acid oxidation disorders are currently developed, based on pharmacological treatment with bezafibrate, and specific diets enriched in medium-chain triglycerides or triheptanoin.     

Disorders of lipid metabolism in muscle

At rest and during sustained exercise, lipids are the main source of energy for muscle. Free fatty acids become available to muscle from plasma free fatty acids and triglycerides, and from intracellular triglyceride lipid droplets. Transport of long-chain fatty acyl groups into the mitochondria requires esterification and de-esterification with carnitine by the “twin” enzymes carnitine palmityltransferase (CPT) I and II, bound to the outer and inner faces of the inner mitochondrial membrane. Carnitine deficiency occurs in two clinical syndromes. (1) In the myopathic form, there is weakness; muscle biopsy shows excessive accumulation of lipid droplets; and the carnitine concentration is markedly decreased in muscle but normal in plasma. (2) In the systemic form, there are weakness and recurrent episodes of hepatic encephalopathy; muscle biopsy shows lipid storage; and the carnitine concentration is decreased in muscle, liver, and plasma. The etiology of carnitine deficiency is not known in either the myopathic or the systemic form, but administration of carnitine or corticosteroids has been beneficial in some patients. “Secondary” carnitine deficiency may occur in patients with malnutrition, liver disease, chronic hemodialysis, and, possibly, mitochondrial disorders. CPT deficiency causes recurrent myoglobinuria, usually precipitated by prolonged exercise or fasting. Muscle biopsy may be normal or show varying degrees of lipid storage. Genetic transmission is probably autosomal recessive, but the great male predominance (20/21) remains unexplained. In many cases, lipid storage myopathy is not accompanied by carnitine or CPT deficiency, and the biochemical error remains to be identified.     

Immunoquantitation of carnitine palmitoyl transferase in skeletal muscle of 31 patients.

We studied 31 patients suspected of having muscle carnitine palmitoyl transferase 2 (CPT2) deficiency. The catalytic activity of CPT2 was measured in muscle biopsies by the isotope exchange method and CPT2 immunoreactivity was quantitated by an enzyme-linked immunosorbent assay. Nine patients had normal enzyme activity and immunoreactivity. Eight patients had significant deficiencies in catalytic activity (> 3 S.D. below reference mean) of which six were also deficient in immunoreactivity. An additional nine patients were significantly deficient in immunoreactivity with normal catalytic activity and five patients had partial deficiencies in both. At least two categories of alterations in CPT may exist which lead to a deficiency based on the data presented: (1) a regulatory defect in CPT which only alters the enzyme active site; and (2) a structural defect due to altered synthesis, increased degradation, or changes in the immunoreactive site. It may prove to be of diagnostic importance to combine the analysis of enzyme activity and immunoreactivity in patients suspected of having a CPT deficiency and to further investigate the condition of partial CPT deficiency.     

Muscle carnitine palmityltransferase deficiency: A case with enzyme deficiency in cultured fibroblasts

A further case of carnitine palmityltransferase (CPT) deficiency in a young man is described, the defect being documented by direct enzyme assays of muscle biopsies. The finding of markedly reduced enzyme activity in the patient's cultured fibroblasts supports the concept that CPT deficiency is a systemic rather than an exclusively muscular condition.     

Diagnostic assessment and long-term follow-up of 13 patients with Very Long-Chain Acyl-Coenzyme A dehydrogenase (VLCAD) deficiency

Very Long-Chain Acyl-CoA dehydrogenase (VLCAD) deficiency is an inborn error of mitochondrial long-chain fatty acid oxidation (FAO) most often occurring in childhood with cardiac or liver involvement, but rhabdomyolysis attacks have also been reported in adults. We report in this study the clinical, biochemical and molecular studies in 13 adult patients from 10 different families with VLCAD deficiency. The enzyme defect was demonstrated in cultured skin fibroblasts or lymphocytes. All patients exhibited exercise intolerance and recurrent rhabdomyolysis episodes, which were generally triggered by strenuous exercise, fasting, cold or fever (mean age at onset: 10 years). Inaugural life-threatening general manifestations also occurred before the age of 3 years in four patients. Increased levels of long-chain acylcarnitines with tetradecenoylcarnitine (C14:1) as the most prominent species were observed in all patients. Muscle biopsies showed a mild lipidosis in four patients. For all patients but two, molecular analysis showed homozygous (4 patients) or compound heterozygous genotype (7 patients). For the two remaining patients, only one mutation in a heterozygous state was detected. This study confirms that VLCAD deficiency, although being less frequent than CPT II deficiency, should be systematically considered in the differential diagnosis of exercise-induced rhabdomyolysis. Measurement of fasting blood acylcarnitines by tandem mass spectrometry allows accurate biochemical diagnosis and should therefore be performed in all patients presenting with unexplained muscle exercise intolerance or rhabdomyolysis.     

Familial combined deficiency of muscle carnitine and carnitine palmityl transferase (CPT)

ABSTRACT— Two patients, brother and sister, aged 19 and 16, with combined, partial deficiency of carnitine palmityltransferase (CPT) are reported. Both patients had recurrent exercise-related myoglobinuria. The brother had also experienced an episode of transient renal failure associated with myoglobinuria. Both had elevated CK and myoglobin in plasma between attacks. There was a normal production of lactate in ischaemic forearm exercise, but elevated levels of NH₃, resulting in an increased NH₃/Iactate ratio; 48-h fasting caused no significant changes in cholesterol, triglycerides or glucose, no rise of CK, and a normal ketogenic response, indicating no hepatic enzyme deficiency. Muscle biopsy showed slight changes of myopathy in both patients, with scattered atrophic fibres, but no lipid accumulation or other specific changes, Biochemical analysis of muscle tissue revealed a reduction of carnitine to 48% and 40% and a reduction of CPT to 55% and 59% of normal values, which is similar to the findings in the only previous report of combined partial carnitine and CPT deficiency. The heterogenity of the laboratory findings in CPT deficiencies and the value of the various diagnostic procedures in metabolic myopathies are discussed.     

Cold induced rhabdomyolysis in carnitine palmyityl transferase deficiency.

A case of carnitine palmityl transferase deficiency in skeletal muscle is described. The usual symptoms associated with this disease (recurrent muscle cramps or pain and pigmenturia) were observed but sudden exposure to cold precipitate rhabdomyolysis in this patient.     

Metabolic causes of myoglobinuria

To evaluate the proportion of cases of myoglobinuria that can be ascribed to specific metabolic defects, we have studied eight enzymes--phosphorylase, phosphorylase kinase, phosphofructokinase (PFK), phosphoglycerate kinase (PGK), phosphoglycerate mutase (PGAM), lactate dehydrogenase (LDH), carnitine palmitoyltransferase (CPT), and myoadenylate deaminase (MAD)--in muscle biopsy specimens from 77 consecutive patients with myoglobinuria (documented in 44, suspected in 33). Enzyme defects were found in 36 patients: CPT deficiency in 17, phosphorylase deficiency in 10, phosphorylase kinase deficiency in 4, MAD deficiency in 3, PGK deficiency in 1, and a combined defect of CPT and MAD in 1. Exercise was the main precipitating factor, both in patients with and in those without detectable enzymopathies. Thirty patients had specific enzymopathies without myoglobinuria: 14 had phosphorylase deficiency, 9 had MAD deficiency, 3 had phosphorylase kinase deficiency, 3 had PFK deficiency, and 1 had PGAM deficiency. Systematic biochemical evaluation of muscle biopsy specimens revealed specific enzymopathies in about half of the patients with idiopathic myoglobinuria. The rest may have blocks of metabolic pathways not yet studied routinely, such as beta oxidation, or genetic defects of the sarcolemma, such as Becker's muscular dystrophy.     

Myoglobinuria and carnitine palmityl transferase deficiency in father and son

Summary A 18-year-old man had recurrent myoglobinuria following exercise and fasting. His parents originated from the same village, which had less than 1000 inhabitants. His 53-year-old father suffered from similar episodes, whereas his mother and elder brother were symptom free. Biochemical investigations on muscle and platelets disclosed carnitine palmityl transferase (CPT) deficiency in the patient and his father. His mother and brother showed intermediate CPT values consistent with their being heterozygotes. This appears to be the first report of CPT deficiency with recurrent myoglobinuria in two generations (so-called quasidominant transmission).