Screening for medium chain acyl-CoA dehydrogenase deficiency using electrospray ionisation tandem mass spectrometry

OBJECTIVE: To establish criteria for the diagnosis of medium chain acyl-CoA dehydrogenase (MCAD) deficiency in the UK population using a method in which carnitine species eluted from blood spots are butylated and analysed by electrospray ionisation tandem mass spectrometry (ESI-MS/MS). DESIGN: Four groups were studied: (1) 35 children, aged 4 days to 16.2 years, with proven MCAD deficiency (mostly homozygous for the A985G mutation, none receiving carnitine supplements); (2) 2168 control children; (3) 482 neonates; and (4) 15 MCAD heterozygotes. RESULTS: All patients with MCAD deficiency had an octanoylcarnitine concentration ([C8-Cn]) > 0.38 microM and no accumulation of carnitine species > C10 or < C6. Among the patients with MCAD deficiency, the [C8-Cn] was significantly lower in children > 10 weeks old and in children with carnitine depletion (free carnitine < 20 microM). Neonatal blood spots from patients with MCAD deficiency had a [C8-Cn] > 1.5 microM, whereas in heterozygotes and other normal neonates the [C8-Cn] was < 1.0 microM. In contrast, the blood spot [C8-Cn] in eight of 27 patients with MCAD deficiency > 10 weeks old fell within the same range as five of 15 MCAD heterozygotes (0.38-1.0 microM). However, the free carnitine concentrations were reduced (< 20 microM) in the patients with MCAD deficiency but normal in the heterozygotes. CONCLUSIONS: Criteria for the diagnosis of MCAD deficiency using ESI-MS/MS must take account of age and carnitine depletion. If screening is undertaken at 7-10 days, the number of false positive and negative results should be negligible. Because there have been no instances of death or neurological damage following diagnosis of MCAD deficiency in our patient group, a strong case can be made for neonatal screening for MCAD deficiency in the UK.     

Screening for medium chain acyl-CoA dehydrogenase deficiency using electrospray ionisation tandem mass spectrometry

OBJECTIVE—To establish criteria for the diagnosis of medium chain acyl-CoA dehydrogenase (MCAD) deficiency in the UK population using a method in which carnitine species eluted from blood spots are butylated and analysed by electrospray ionisation tandem mass spectrometry (ESI-MS/MS).DESIGN—Four groups were studied: (1) 35 children, aged 4 days to 16.2 years, with proven MCAD deficiency (mostly homozygous for the A985G mutation, none receiving carnitine supplements); (2) 2168control children; (3) 482 neonates; and (4) 15 MCAD heterozygotes.RESULTS—All patients with MCAD deficiency had an octanoylcarnitine concentration ([C8-Cn]) > 0.38 µM and no accumulation of carnitine species > C₁₀ or < C₆. Among the patients with MCAD deficiency, the [C₈-Cn] was significantly lower in children > 10 weeks old and in children with carnitine depletion (free carnitine < 20 µM). Neonatal blood spots from patients with MCAD deficiency had a [C8-Cn] > 1.5 µM, whereas in heterozygotes and other normal neonates the [C8-Cn] was < 1.0 µM. In contrast, the blood spot [C8-Cn] in eight of 27 patients with MCAD deficiency > 10 weeks old fell within the same range as five of 15 MCAD heterozygotes (0.38-1.0 µM). However, the free carnitine concentrations were reduced (< 20 µM) in the patients with MCAD deficiency but normal in the heterozygotes.CONCLUSIONS—Criteria for the diagnosis of MCAD deficiency using ESI-MS/MS must take account of age and carnitine depletion. If screening is undertaken at 7-10 days, the number of false positive and negative results should be negligible. Because there have been no instances of death or neurological damage following diagnosis of MCAD deficiency in our patient group, a strong case can be made for neonatal screening for MCAD deficiency in the UK.     

Urinary medium-chain acylcarnitines in medium-chain acyl-CoA dehydrogenase deficiency, medium-chain triglyceride feeding and valproic acid therapy: sensitivity and specificity of the radioisotopic exchange/high performance liquid chromatography method.

To determine the sensitivity and specificity of detecting urinary medium-chain acylcarnitines for the diagnosis of MCAD deficiency, 114 urine specimens from 75 children with metabolic diseases and controls were analyzed in a blinded fashion using a radioisotopic exchange/HPLC method. All 47 patients with MCAD deficiency were correctly diagnosed using the criterion hexanoylcarnitine or octanoylcarnitine peak areas larger than those of other medium-chain acylcarnitines. The majority of them were tested during the asymptomatic state without L-carnitine loading. Four patients with other defects of fatty acid oxidation and three patients receiving valproic acid had a similar acylcarnitine excretion pattern. To further examine the specificity of the method, eight infants receiving a diet enriched with medium-chain triglycerides and 13 additional patients receiving valproic acid were studied. Most of these also tested positive for MCAD deficiency by the above criterion. Analysis by a new gas chromatographic-mass spectrometric procedure revealed that octanoylcarnitine, not valproylcarnitine, was the most abundant medium-chain carnitine ester excreted by a patient treated with valproic acid. Quantitation of urinary hexanoylcarnitine and octanoylcarnitine showed considerable overlap among patients with MCAD deficiency and those receiving valproic acid or a medium-chain triglyceride-enriched diet. MCAD deficiency can be reliably detected in urine specimens by this method without the need for prior carnitine loading. However, other defects in fatty acid oxidation must be differentiated from MCAD deficiency, and a history of medium-chain triglyceride or valproic acid administration must be considered if the diagnosis of MCAD deficiency is sought through analysis of urinary acylcarnitines.     

Early diagnosis and treatment of neonatal medium-chain acyl-CoA dehydrogenase deficiency: Report of two siblings

Two siblings are reported who were syptomatic in the neonatal period. The first died suddenly at 4 days of age after regurgitating a meal. The postmortem examination showed steatosis of the liver, kidney and muscle. In the second, medium-chain acyl-CoA dehydrogenase (MCAD) deficiency was diagnosed at 3 days of age with muscular hypotonia, vomiting, hyperammonaemia and mild acidosis. Thus disorders of fatty acid oxidation should also be considered in newborns. The biochemical work up indicates that in neonates, analysis of serum medium-chain fatty acids and of acyl and free carnitine are more likely to lead to a diagnosis than determining dicarboxylic acids alone in urine. Long-term treatment was effective and monitored by the acyl/free carnitine ratio.An abstract relating the initial findings of this patient was published by Catzeflis C, Délèze G, Kuchler H, Spahr A, Schütz B, Bachmann C (1987) Helv Paediatr Acta 42:47     

Medium-chain acyl-CoA dehydrogenase deficiency: Molecular aspects

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an autosomal recessive disorder which is known to cause Reye-like syndrome in children and sudden infant death. A point mutation of lysine329-to-glutamic acid329 substitution in the MCAD gene was recently identified as the most common mutation in patients with MCAD deficiency. This mutation is responsible for about 90% of mutant MCAD alleles in Caucasians. Patients with this type of mutation have a variety of symptoms, indicating that the clinical heterogeneity of MCAD deficiency may not be caused entirely by genetic heterogeneity. Screening for the mutation among newborns in England, Australia, and United States of America indicates the prevalence of carriers to be 1 in 40-107, suggesting the high incidence of the mutation. Since presymptomatic diagnosis and appropriate dietary management are important in MCAD deficiency to prevent life-threatening complications, the relatively high incidence of this disorder may warrant population screening. The most common MCAD mutation can now be detected by DNA diagnostic methods using Guthrie cards. This makes it possible to screen a population efficiently for this potentially fatal disorder.     

Biosynthesis of variant medium chain acyl-CoA dehydrogenase in cultured fibroblasts from patients with medium chain acyl-CoA dehydrogenase deficiency

We prepared monospecific antiserum in rabbits against medium chain acyl-CoA dehydrogenase (MCAD) purified from rat liver and studied the biosynthesis of MCAD in cultured skin fibroblasts from patients with MCAD deficiency using the antibody. Cells were incubated with [35S]methionine. The labeled MCAD was immunoprecipitated using the anti-rat MCAD antiserum and Staphylococcus aureus cells and then analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We first demonstrated that antirat MCAD antibody crossreacted specifically with human MCAD. In 13 MCAD-deficient cell lines tested, the residual MCAD activity ranged from 5-12% of the mean of normal controls, but the variant MCAD in all of these cells was indistinguishable from the normal human MCAD on the basis of molecular size, indicating that MCAD deficiency in all of these patients is most likely due to point mutation(s) in the MCAD gene.     

The enzymatic basis for the dehydrogenation of 3-phenylpropionic acid: in vitro reaction of 3-phenylpropionyl-CoA with various acyl-CoA dehydrogenases

3-Phenylpropionic acid is an end-product of the bacterial degradation of unabsorbed phenylalanine in the intestinal lumen. As CoA ester, this metabolite has been considered to be a specific substrate for medium chain acyl-CoA dehydrogenase (MCAD). Its glycine-conjugate, 3-phenylpropionylglycine, has now been established as a pathognomonic marker in urine from patients affected with MCAD deficiency. However, no systematic studies to evaluate the reactivity of 3-phenylpropionyl-CoA with other known acyl-CoA dehydrogenases have so far been carried out to establish the specificity of this substrate for MCAD. We studied the in vitro reactivity of 3-phenylpropionyl-CoA with five rat and human liver acyl-CoA dehydrogenases using purified preparations. we demonstrated that MCAD effectively dehydrogenated 3-phenylpropionyl-CoA, and that no other acyl-CoA dehydrogenase exhibited any significant activity with this substrate. In the steady state condition, the Km of 3-phenylpropionyl-CoA for human MCAD was 50 microM. Gas chromatography/mass spectrometry analysis of the assay mixture identified trans-cinnamoyl-CoA as the product of the reaction. Furthermore, we showed by determination of the reaction products using gas chromatography/mass spectrometry selected ion monitoring that, in absence of the primary electron acceptor, 3-phenylpropionyl-CoA was slowly but significantly dehydrogenated by MCAD under aerobic conditions. These data suggest that MCAD may oxidize 3-phenylpropionyl-CoA in vivo using an alternative electron acceptor, to produce trans-cinnamoyl-CoA. This mechanism provides an explanation for the normal 3-phenylpropionylglycine excretion observed in urine from patients affected with glutaric aciduria type II and ethylmalonic/adipic aciduria.     

Immunochemical characterization of variant medium-chain acyl-CoA dehydrogenase in fibroblasts from patients with medium-chain acyl-CoA dehydrogenase deficiency.

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a common autosomal recessive disorder of mitochondrial fatty acid oxidation characterized by episodes of hypoketotic hypoglycemia usually beginning in the first 2 y of life. We previously showed, in pulse labeling experiments, that the biosynthesis and immediate posttranslational processing of MCAD are normal in fibroblasts from patients with MCAD deficiency. Most patients studied to date are homozygous for a point mutation (A985-G) that results in the substitution of glutamate for lysine ar residue 304 of the mature MCAD subunit. We performed immunoblot analysis of fibroblast MCAD from a total of 34 patients with MCAD deficiency, including 31 homozygous for the A985-G mutation, using a rabbit anti-rat MCAD antibody that cross-reacted specifically with human MCAD, but not with the related enzymes, short-chain and long-chain acyl-CoA dehydrogenases. All patients with the A985-G mutation lacked detectable MCAD. Pulse-chase labeling of MCAD-deficient fibroblasts with 35S-methionine demonstrated that this variant MCAD was unstable compared to controls. Taken together, these data suggest that this mutation affects the stability of MCAD protein within the mitochondrial matrix.     

Medium-chain acyl-CoA dehydrogenase deficiency does not correlate with apparent life-threatening events and the sudden infant death syndrome: results from phenylpropionate loading tests and DNA analysis

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common inherited disorder of fatty acid metabolism and typically presents in early childhood as potentially fatal hypoketotic, hypoglycaemic crisis often associated with Reye-like symptoms. Re-investigations of cases of sudden infant death syndrome (SIDS) have revealed in some instances a deficiency of MCAD, suggesting that this metabolic disorder may lead to sudden infant death without prior clinical symptoms. In the present study, we examined 142 infants who had suffered from an apparent life-threatening event (ALTE) or were otherwise considered at risk for SIDS for MCAD deficiency by phenylpropionate loading. In no case excretion of phenylpropionylglycine, the hallmark of MCAD deficiency, was increased. In contrast, 3 out of 55 children with symptoms of metabolic disorders showed increased phenylpropionylglycine excretion, and in all three cases MCAD deficiency was confirmed by DNA analysis. In addition, we investigated 142 cases of sudden unexplained child death and 100 control subjects for the A985G mutation in the MCAD gene which is associated with about 98% of enzyme deficiencies. We found one case of heterozygosity each in the patient and control group. Our data indicate that MCAD deficiency is not a major cause of ALTE and, in agreement with results from similar studies in other countries, its frequency is not increased in children who died of SIDS.     

Short-chain acyl-coenzyme A dehydrogenase activity, antigen, and biosynthesis are absent in the BALB/cByJ mouse.

BALB/cByJ (J) mice have short-chain acyl-CoA dehydrogenase (SCAD) deficiency and an organic aciduria similar to that of human SCAD deficiency. [9,10(n)-3H]- and [15,16(n)-3H]palmitate oxidations in J mouse fibroblasts were 96 and 35% of control, respectively, consistent with an isolated SCAD defect. Acyl-CoA dehydrogenase activities were assayed in muscle and fibroblast mitochondria from BALB/cBy controls (Y) and SCAD-deficient J mice. Medium-chain acyl-CoA dehydrogenase (MCAD) activities were comparable in both J and Y mice from all tissues. In the presence of MCAD antiserum, SCAD activities in J mice were undetectable in both tissues. Apparent Km and Vmax values in liver mitochondria suggested a somewhat increased affinity of MCAD for butyryl-CoA in J mice, as compared with MCAD from other species. Immunoblot studies using mitochondria revealed identical apparent SCAD molecular weight in liver, muscle, and fibroblasts from Y mice and no detectable SCAD antigen in J mice; MCAD antigen was detected in comparable amounts from both Y and J mice. Radiolabeling and immunoprecipitation studies in J mouse fibroblasts revealed no SCAD synthesis, but normal MCAD synthesis. These data argue against the existence of tissue-specific SCAD isoforms in the mouse and confirm that this mouse strain is a model for the human organic aciduria resulting from this beta-oxidation defect.     

Frequency of 985A-to-G mutation in medium-chain acyl-CoA dehydrogenase gene among patients with sudden infant death syndrome,Reye syndrome,severe motor and intellectual disabilities and healthy newborns in Japan

The prevalence of the ⁹⁸⁵A-to-G mutation in the medium-chain acyl-CoA dehydrogenase (MCAD) gene among Japanese patients with sudden infant death syndrome, Reye syndrome, unknown fatty acid oxidation disorders and severe motor and intellectual disabilities was studied using the PCR/Nco-I method for molecular diagnosis. A frequency study of this common mutation was also conducted on blood samples and left over Guthrie cards from 329 healthy newborns in Japan. Neither heterozygotes nor homozygotes for the ⁹⁸⁵A-to-G mutation were identified among both patients and controls. The result of the present study accord with previous reports that MCAD deficiency is a common disorder in Caucasians, but quite rare among Japanese. Therefore, newborn mass-screening for MCAD deficiency using this method will not be practical in Japan. However, it still seems necessary to investigate a child with fatty acid oxidation disorder for the presence of MCAD deficiency, using both biochemical and molecular genetic methods.     

Recognition of medium-chain acyl-CoA dehydrogenase deficiency in asymptomatic siblings of children dying of sudden infant death or Reye-like syndromes

The medium-chain acyl-CoA dehydrogenase (MCAD) deficiency of mitochondrial beta oxidation has been identified in two asymptomatic siblings in a family in which two previous deaths had been recorded, one attributed to sudden infant death syndrome and the other to Reye syndrome. Recognition of this disorder in one of the deceased and in the surviving siblings was accomplished by detection of a diagnostic metabolite, octanoylcarnitine, using a new mass spectrometric technique. This resulted in early treatment with L-carnitine supplement in the survivors, which should prevent metabolic deterioration. Further studies suggest that breast-feeding may be protective for infants with MCAD deficiency. Families with children who have had Reye syndrome or in which sudden infant death has occurred are at risk for MCAD deficiency. We suggest that survivors and asymptomatic siblings should be tested for this treatable disorder.     

Outcome of medium chain acyl-CoA dehydrogenase deficiency after diagnosis

BACKGROUND—Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common inborn error of fatty acid metabolism. Undiagnosed, it has a mortality rate of 20-25%. Neonatal screening for the disorder is now possible but it is not known whether this would alter the prognosis.OBJECTIVE—To investigate the outcome of MCAD deficiency after the diagnosis has been established.METHOD—All patients with a proved diagnosis of MCAD deficiency attending one centre in a four year period were reviewed.RESULTS—Forty one patients were identified. Follow up was for a median of 6.7 years (range, 9 months to 14 years). Nearly half of the patients were admitted to hospital with symptoms characteristic of MCAD deficiency before the correct diagnosis was made. After diagnosis, two patients were admitted to hospital with severe encephalopathy but there were no additional deaths or appreciable morbidity. There was a high incidence (about one fifth) of previous sibling deaths among the cohort.CONCLUSIONS—Undiagnosed, MCAD deficiency results in considerable mortality and morbidity. However, current management improves outcome, supporting the view that the disorder should be included in newborn screening programmes.     

Newborn screening with tandem mass spectrometry: examining its cost-effectiveness in the Wisconsin Newborn Screening Panel

OBJECTIVE: To examine the cost-effectiveness of tandem mass spectrometry (MS/MS) in a neonatal screening panel for 14 fatty acid oxidation and organic acidemia disorders in the Wisconsin Newborn Screening Program. STUDY DESIGN: An incremental cost-effectiveness analysis with a hypothetical cohort of 100,000 infants was performed. A threshold of $50,000/QALY (quality-adjusted life-year) was used to determine whether screening for medium-chain acyl-CoA dehydrogenase deficiency (MCAD) alone is cost-effective or whether additional disorders would need to be incorporated into the analysis to arrive at a conclusion regarding the overall cost-effectiveness of MS/MS. RESULTS: Under conservative assumptions, screening for MCAD alone yields an incremental cost-effectiveness ratio of $41,862/QALY. With the use of more realistic assumptions, screening becomes more cost-effective ($6008/QALY) and remains cost-effective so long as the incremental cost of screening remains under $13.05 per test. Adding the incremental costs of detecting the 13 other disorders on the screening panel still yields a result well within accepted norms for cost-effectiveness ($15,252/QALY). CONCLUSIONS: In Wisconsin, MS/MS screening for MCAD alone appears to be cost-effective. Future analyses should examine the cost-effectiveness of alternative follow-up and treatment regimens for MCAD and other panel disorders.     

Metabolic defects with hypoketotic hypoglycemia

Metabolic defects resulting in hypoketotic hypoglycemia can lead to hepato-encephalopathy and can be lethal. Recognition of the association of hypoglycemia with hypoketonemia is essential for efficient diagnostic and therapeutic procedures. The pattern of urinary excretion of organic acids is useful in differential diagnosis between the possible metabolic defects, viz. carnitine deficiency, carnitine palmitoyl transferase deficiency, medium-chain, long-chain and multiple acyl-CoA dehydrogenase deficiencies, and HMG-CoA lyase deficiency. These (except for carnitine deficiency) can be confirmed by enzyme activity measurements in cultured fibroblasts and tissue biopsies and prenatally. Treatment is available for all of them except some cases of multiple acyl-CoA dehydrogenase deficiency. Genetic counselling of the families must be based on a precise biochemical diagnosis.     

Outcome of medium chain acyl-CoA dehydrogenase deficiency after diagnosis.

BACKGROUND: Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common inborn error of fatty acid metabolism. Undiagnosed, it has a mortality rate of 20-25%. Neonatal screening for the disorder is now possible but it is not known whether this would alter the prognosis. OBJECTIVE: To investigate the outcome of MCAD deficiency after the diagnosis has been established. METHOD: All patients with a proved diagnosis of MCAD deficiency attending one centre in a four year period were reviewed. RESULTS: Forty one patients were identified. Follow up was for a median of 6.7 years (range, 9 months to 14 years). Nearly half of the patients were admitted to hospital with symptoms characteristic of MCAD deficiency before the correct diagnosis was made. After diagnosis, two patients were admitted to hospital with severe encephalopathy but there were no additional deaths or appreciable morbidity. There was a high incidence (about one fifth) of previous sibling deaths among the cohort. CONCLUSIONS: Undiagnosed, MCAD deficiency results in considerable mortality and morbidity. However, current management improves outcome, supporting the view that the disorder should be included in newborn screening programmes.     

Acquired carnitine abnormalities in critically ill children

In order to characterize the role of carnitine during metabolic stress, we prospectively determined carnitine profiles in plasma and urine on admission, days 2, 5, 10 and 15, among 28 critically ill children free of any known conditions associated with secondary carnitine deficiency. More than 25% of plasma and 50% of urinary carnitine measurements were abnormal; 96% (27/28) of patients displayed on at least one occasion an abnormal [<−2 SD or >+2 SD] carnitine value in plasma. Three children had extremely low [<10 μmol/l] free carnitine (FC) levels in plasma. Plasma esterified and FC levels on admission were not related to the risk of mortality [PRISM score], to muscle lysis [CK values], and to the caloric intake. Levels of FC and esterified carnitine in plasma were unrelated to those measured in urine. Conclusion Abnormal plasma and urine carnitine measurements are frequently found in critically ill children; the biological significance of these perturbations remains unclear. Caution must be exercised before concluding that an abnormal carnitine value is indicative of an underlying hereditary metabolic disorder in this population. Received: 7 March 1996 / Accepted: 14 April 1997     

Medium-Chain Acyl-Coa Dehydrogenase Deficiency: Postmortem Diagnosis in a Case of Sudden Infant Death and Neonatal Diagnosis of an Affected Sibling

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an inherited disorder of fatty acid oxidation associated with sudden death in infants and, in its fulminant form(s), a Reye-like syndrome. In an 18-month-old female who died suddenly and unexpectedly, the postmortem diagnosis of MCAD deficiency was made by analysis of organic acids, acylglycines, and acylcarnitines and by analysis of the most common mutation causing MCAD deficiency (A985G) in a sample of heart blood obtained at autopsy and frozen at—20° C for 8 months. The patient was homozygous for A985G and metabolites characteristic of MCAD deficiency were identified. Parents and an older sibling were heterozygous for A985G. The mother was 6 months pregnant when the results were known. At the birth of her male infant, blood spot cards and urine were obtained. The infant was homozygous for A985G by analysis of DNA extracted from blood spots and he excreted metabolites characteristic of MCAD deficiency. These results demonstrate the use of novel molecular and metabolite analysis in making the postmortem diagnosis of MCAD deficiency. The neonatal diagnosis of an affected sib permits the institution of appropriate dietary measures to prevent potentially fatal episodes of illness.     

Medium-chain acyl-CoA dehydrogenase deficiency: postmortem diagnosis in a case of sudden infant death and neonatal diagnosis of an affected sibling.

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an inherited disorder of fatty acid oxidation associated with sudden death in infants and, in its fulminant form(s), a Reye-like syndrome. In an 18-month-old female who died suddenly and unexpectedly, the postmortem diagnosis of MCAD deficiency was made by analysis of organic acids, acylglycines, and acylcarnitines and by analysis of the most common mutation causing MCAD deficiency (A985G) in a sample of heart blood obtained at autopsy and frozen at -20 degrees C for 8 months. The patient was homozygous for A985G and metabolites characteristic of MCAD deficiency were identified. Parents and an older sibling were heterozygous for A985G. The mother was 6 months pregnant when the results were known. At the birth of her male infant, blood spot cards and urine were obtained. The infant was homozygous for A985G by analysis of DNA extracted from blood spots and he excreted metabolites characteristic of MCAD deficiency. These results demonstrate the use of novel molecular and metabolite analysis in making the postmortem diagnosis of MCAD deficiency. The neonatal diagnosis of an affected sib permits the institution of appropriate dietary measures to prevent potentially fatal episodes of illness.     

LOW SERUM CARNITINE CONCENTRATIONS IN HEALTHY CHILDREN WITH IRON DEFICIENCY ANEMIA

Carnitine is not only obtained from animal-derived foods but also synthesized in the body. It plays an important role in the energy metabolism of many tissues, including heart and skeletal muscles. Iron is known to be essential for the biosynthesis of carnitine. Although many conditions are well known to cause secondary carnitine deficiency, iron deficiency, which is a very common condition in children, is not well studied as a cause of secondary carnitine deficiency in humans. This study demonstrates the coexistence of iron deficiency and low carnitine levels in otherwise healthy children. The mean carnitine concentration of 18 otherwise healthy children with iron deficiency anemia was significantly lower compared to the mean carnitine concentration of healthy children without iron deficiency anemia. Based on the evidence about the effect of low iron on carnitine stores in experimental animals, we proposed that low serum carnitine levels in these children may be secondary to iron deficiency. However, further studies need to be done to further clarify this relationship.