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In a personal series of 107 patients, we describe clinical presentations, methods of recognition and therapeutic management of inherited fatty acid oxidation (FAO) defects. As a whole, FAO disorders appear very severe: among the 107 patients, only 57 are still living. Including 47 siblings who died early in infancy, in total 97 patients died, of whom 30% died within the first week of life and 69% before 1 year. Twenty‐eight patients presented in the neonatal period with sudden death, heart beat disorders, or neurological distress with various metabolic disturbances. Hepatic presentations were observed in 73% of patients (steatosis, hypoketotic hypoglycaemia, hepatomegaly, Reye syndrome). True hepatic failure was rare (10%); cholestasis was observed in one patient with LCHAD deficiency. Cardiac presentations were observed in 51% of patients: 67% patients presented with cardiomyopathy, mostly hypertrophic, and 47% of patients had heart beat disorders with various conduction abnormalities and arrhythmias responsible for collapse, near‐miss and sudden unexpected death. All enzymatic blocks affecting FAO except CPT I and MCAD were found associated with cardiac signs. Muscular signs were observed in 51% of patients (of whom 64% had myalgias or paroxysmal myoglobinuria, and 29% had progressive proximal myopathy). Chronic neurologic presentation was rare, except in LCHAD deficiency (retinitis pigmentosa and peripheral neuropathy). Renal presentation (tubulopathy) and transient renal failure were observed in 27% of patients. The diagnosis of FAO disorders is generally based on the plasma acylcarnitine profile determined by FAB‐MS/MS from simple blood spots collected on a Guthrie card. Urinary organic acid profile and total and free plasma carnitine can also be very helpful, mostly in acute attacks. If there is no significant disturbance between attacks, the diagnosis is based upon a long‐chain fatty acid loading test, fasting test, and in vitro studies of fatty acid oxidation on fresh lymphocytes or cultured fibroblasts. Treatment includes avoiding fasting or catabolism, suppressing lipolysis, and carnitine supplementation. The long‐term dietary therapy aims to prevent periods of fasting and restrict long‐chain fatty acid intake with supplementation of medium‐chain triglycerides. Despite these therapeutic measures, the long‐term prognosis remains uncertain.

Pyruvate dehydrogenase complex (PDHc) is a thiamine dependent key enzyme for energy production which catalyses decarboxylation of pyruvate into acetyl CoA for the Krebs cycle. 1 PDHc deficiency is generally (80%) caused by mutations in the E1[alpha] subunit gene, PDHA1, located on chromosome Xp22.1, but other genes have been reported to be mutated (eg, PDHX, encoding the E3 binding protein, DLAT, encoding the E2 subunit PDHX, and PDHB, encoding the E1 beta subunit). Most had episodes of ataxia, confusion, muscle weakness or hyperventilation triggered by high sugar intake or fever since childhood. 1 2 Rare cases with adult onset progressive movement disorders (chorea, parkinsonism), cognitive deficit and bilateral necrotic lesions of the putamina and pallidum were also reported. 3 Optic neuropathy is a classical feature of energy metabolism disorders.

The oxidation of long‐chain fatty acids in mitochondria plays an important role in energy production, especially in skeletal muscle, heart and liver. Long‐chain fatty acids, activated to their CoA esters in the cytosol, are shuttled across the barrier of the inner mitochondrial membrane by the carnitine cycle. This pathway includes four steps, mediated by a plasma membrane carnitine transporter, two carnitine palmitoyltransferases (CPT I and CPT II) and a carnitine‐acylcarnitine translocase. Defects in activation and uptake of fatty acids affect these four steps: CPT II deficiency leads to either exercise‐induced rhabdomyolysis in adults or hepatocardiomuscular symptoms in neonates and children. The three other disorders of the carnitine cycle have an early onset. Hepatic CPT I deficiency is characterized by recurrent episodes of Reye‐like syndrome, whereas severe muscular and cardiac signs are associated with episodes of fasting hypoglycaemia in defects of carnitine transport and translocase. Convenient metabolic investigations for reaching the diagnosis of carnitine cycle disorders are determination of plasma free and total carnitine concentrations, determination of plasma acylcarnitine profile by tandem mass spectrometry and in vitro fatty acid oxidation studies, particularly in fresh lymphocytes. Application of the tools of molecular biology has greatly aided the understanding of the carnitine palmitoyltransferase enzyme system and confirmed the existence of different related genetic diseases. Mutation analysis of CPT II defects has given some clues for correlation of genotype and phenotype. The first molecular analyses of hepatic CPT I and translocase deficiencies were recently reported.

Mitochondrial respiratory chain complex III (ubiquinol-cytochrome c reductase) consists of 11 subunits, only one (cytochrome b) being encoded by the mitochondrial DNA. Disorders of complex III are comparatively rare but are nevertheless present as a clinically heterogeneous group of diseases. To date, no mutation in any of the nuclear-encoded subunits has been described. We report here a deletion in the nuclear gene UQCRB encoding the human ubiquinone-binding protein of complex III (QP-C subunit or subunit VII) in a consanguineous family with an isolated complex III defect. In the proband, a homozygous 4-bp deletion was identified at nucleotides 338-341 of the cDNA predicting both a change in the last seven amino acids and an addition of a stretch of 14 amino acids at the C-terminal end of the protein. Both parents were found to be heterozygous for the deletion, which was absent from 55 controls. Low temperature (-196 degrees C) spectral studies performed on isolated mitochondria from cultured skin fibroblast of the proband showed a decreased cytochrome b content suggestive of a role for the QP-C subunit in the assembly or maintenance of complex III structure.

A North African boy, the son of consanguineous parents, presented at 8 years of age with hypophosphataemic rickets due to De Toni–Debré–Fanconi syndrome. Hepatomegaly and abnormalities of carbohydrate metabolism were suggestive of Fanconi–Bickel syndrome. This was confirmed by the detection of a mutation within GLUT2, the gene encoding the liver‐type facilitative glucose transporter. The study of the respiratory chain revealed a deficiency of complexes I, III and IV in muscle. Mechanisms responsible for an impairment of mitochondrial function, which we interpret as a secondary phenomenon, are discussed.

Carnitine palmitoyltransferase 2 (CPT2) deficiency, the most common inherited disease of the mitochondrial long‐chain fatty acid (LCFA) oxidation, may result in distinct clinical phenotypes, namely a mild adult muscular form and a severe hepatocardiomuscular disease with an onset in the neonatal period or in infancy. In order to understand the mechanisms underlying the difference in severity between these phenotypes, we analyzed a cohort of 20 CPT2‐deficient patients being affected either with the infantile (seven patients) or the adult onset form of the disease (13 patients). Using a combination of direct sequencing and denaturing gradient gel electrophoresis, 13 CPT2 mutations were identified, including five novel ones, namely: 371G>A (R124Q), 437A>C (N146T), 481C>T (R161W), 983A>G (D328G), and 1823G>C (D608H). After updating the spectrum of CPT2 mutations (n=39) and genotypes (n=38) as well as their consequences on CPT2 activity and LCFA oxidation, it appears that both the type and location of CPT2 mutations and one or several additional genetic factors to be identified would modulate the LCFA flux and therefore the severity of the disease. Hum Mutat 21:493–501, 2003. © 2003 Wiley‐Liss, Inc.

A patient with a severe phenotype of carnitine-acylcarnitine translocase deficiency (CATR)(McKusick 212138) is reported. Prior to birth, a defect in beta-oxidation was suspected because of neonatal death of six siblings. Dietary treatment during neonatal adaptation and the subsequent six months of life and a trial of carnitine supplementation are reported. The rapidity with which long chain fatty acid metabolites can accumulate and induce secondary carnitine deficiency within a few hours after birth in an infant with CATR is noteworthy. High rates of glucose suppressed neonatal lipolysis in this infant, but did not seem sufficient to avoid secondary carnitine deficiency as in severe forms of CATR. Therefore simultaneous use of insulin and glucose may be necessary to control neonatal lipolysis. Carnitine supplementation and the possible adverse effects of MCT systematically administrated, should be further assessed in patients with CATR.

Bromocriptine combined with galactose restriction in the matenal diet seems to be partially effective in decreasing endogenous lactose and galactose synthesis, monitored in a pregnant woman heterozygous for galactosaemia at risk of producing a homozygous infant.

Bromocriptine combined with galactose restriction in the matenal diet seems to be partially effective in decreasing endogenous lactose and galactose synthesis, monitored in a pregnant woman heterozygous for galactosaemia at risk of producing a homozygous infant.