Barth's syndrome-like disorder: a new phenotype with a maternally inherited A3243G substitution of mitochondrial DNA (MELAS mutation).

An Argentine male child died at 4.5 years of age of a lethal mitochondrial disease associated with a MELAS mutation and a Barth syndrome-like presentation. The child had severe failure to thrive from the early months and for approximately two years thereafter. In addition, the patient had severely delayed gross motor milestones, marked muscle weakness, and dilated cardiomyopathy that progressed to congestive heart failure. He also had persistently elevated urinary levels of 3-methylglutaconic and 2-ethylhydracrylic acids and low blood levels of cholesterol. Detailed histopathologic evaluation of the skeletal muscle biopsy showed high activity of succinate dehydrogenase, a generalized decrease of COX activity, and abundant ragged-red fibers. Electron microscopic studies revealed multiple mitochondrial abnormalities in lymphocytes and monocytes, in the striated muscle, and in the postmortem samples (muscle, heart, liver, and brain). Biochemical analysis showed a pronounced and constant lactic acidosis, and abnormal urinary organic acid excretion (unchanged in the fasting and postprandial states). In addition, in CSF there was a marked increase of lactate and beta-hydroxybutyrate (beta-HOB) and also a high systemic ratio beta-HOB/acetoacetate. Enzymatic assay of the respiratory chain in biopsied muscle showed 10% of complex I activity and 24% of complex IV activity compared with controls. Molecular studies of the mitochondrial genome revealed an A to G mutation at nucleotide pair 3243 in mitochondrial DNA, a well-known pathogenetic mutation (MELAS mutation) in all the patient's tissues and also in the blood specimens of the probands mother and sibs (4 of 5). The diagnosis of MELAS mutation was reinforced by the absence of an identifiable mutation in the X-linked G4.5 gene of the propositus. The present observation gives additional evidence of the variable clinical expression of mtDNA mutations in humans and demonstrates that all clinical variants deserve adequate investigation to establish a primary defect. It also suggests adding Barth-like syndrome to the list of phenotypes with the MELAS mutation.

Histoenzymology of oxidases and dehydrogenases in peripheral blood lymphocytes and monocytes for the study of mitochondrial oxidative phosphorylation.

Histoenzymological methods usually performed on muscle fibres have been adapted to assess the functioning of oxidative phosphorylation in human circulating blood lymphocytes and monocytes. Oxidases and dehydrogenases were analysed in lymphocyte/monocyte smears. The specificity of each histoenzymological reaction was tested using a specific respiratory chain inhibitor: rotenone for NADH diaphorase, thenoyltrifluoroacetone for succinate dehydrogenase, potassium cyanide for cytochrome c oxidase and oligomycin for ATPase. Complex I activity was detected, but inhibition with rotenone was incomplete. Complexes II, IV and V were almost completely inhibited. These observations indicate that histoenzymology is a valuable method for detecting the activity of these oxidative phosphorylation enzymes in lymphocytes and monocytes. The histoenzymology tests performed on fresh peripheral blood cells resembled those used for muscle biopsies. They could be useful for the diagnosis of respiratory chain disorders in patients.

Enzymatic method for branched chain alpha-ketoacid determination: application to rapid analysis of urine and plasma samples from maple syrup urine disease patients.

A new method for the determination of branched-chain alpha-ketoacid concentration using lactate dehydrogenase (E C 1.1.1.27) isozyme C4 (LDH C4) from mouse testes is proposed. The assay is performed on urine and plasma without previous treatment. Alpha-ketoglutarate and pyruvate are determined on the same sample using glutamate dehydrogenase (GDH, EC 1.4.1.2) and lactate dehydrogenase isozyme A4 (LDH5) respectively and subtracted from the total alpha-ketoacid concentration obtained with LDH C4. This value corresponds to the branched chain alpha-ketoacid. Results were linear within the concentration range 8 to 170 mumoles/L. Detection limit was 8 mumoles/L. Analytical recovery was higher than 91%. For microplate assays, recoveries were higher than 84% and the detection limit was 20 mumoles/L. Determinations performed with GDH, LDH A4 and LDH C4 allow differentiation of E3 deficiency from other clinical phenotypes of maple syrup urine disease. The method is simple and fast, and adaptation to microplates would allow screening of newborns.

Enzymatic method for branched chain alpha-ketoacid determination: application to rapid analysis of urine and plasma samples from maple syrup urine disease patients.

A new method for the determination of branched-chain alpha-ketoacid concentration using lactate dehydrogenase (E C 1.1.1.27) isozyme C4 (LDH C4) from mouse testes is proposed. The assay is performed on urine and plasma without previous treatment. Alpha-ketoglutarate and pyruvate are determined on the same sample using glutamate dehydrogenase (GDH, EC 1.4.1.2) and lactate dehydrogenase isozyme A4 (LDH5) respectively and subtracted from the total alpha-ketoacid concentration obtained with LDH C4. This value corresponds to the branched chain alpha-ketoacid. Results were linear within the concentration range 8 to 170 mumoles/L. Detection limit was 8 mumoles/L. Analytical recovery was higher than 91

. For microplate assays, recoveries were higher than 84

and the detection limit was 20 mumoles/L. Determinations performed with GDH, LDH A4 and LDH C4 allow differentiation of E3 deficiency from other clinical phenotypes of maple syrup urine disease. The method is simple and fast, and adaptation to microplates would allow screening of newborns.

[Mitochondrial 2-methylacetoacetyl-CoA thiolase deficiency in Argentina]. / Deficiencia de la 2-metilacetoacetil-CoA tiolasa mitocondrial en Argentina.

From the description of two pairs of siblings belonging to unrelated families, one Argentine family with a history of consanguinity and Irish ancestry and the other family native of Paraguay, in whom mitochondrial 2-methylacetoacetyl-CoA thiolase deficiency, commonly known as beta-ketothiolase deficiency (beta-KTD, McKusick 203750; EC 2.3.1.9) was recognized. We tried to outline through this experience the clinical and biochemical consequences of this genetic defect in the 6th step of the isoleucine catabolism. The phenotyoic expression presented by the patients belonged to the classical form of beta-KTD. Seven to 15 months was the age at onset of the uniform clinical pattern this being essentially an association of one or several severe ketoacidotic episodes and hyperglycemia which was observed in two patients. The thin-layer chromatography of the tiglylglycine, and dinitrophenylhydrazone of the butanone were positive; aminoacidemia and aminoaciduria revealed normal levels. The organic acids having a unique profile obtained through gaschromatography and mass-spectrometry (GC/MS) showed excretion of large quantities of metabolites characteristic of the disease: 2-methyl-3-hydroxybutirate, 2-methylacetoacetic acid, tiglylglycine and 2-ethylhydracrilic acid which led us to establish the biochemical diagnosis of beta-KTD. The assay of the beta-ketothiolase in lymphocytes and polymorphonuclear leukocytes of the only surviving patient (VT) showed absence of activation by the K+ ion when the acetoacetyl-CoA was used as a substrate. This first Argentine report about beta-KTD leads us to mention three amplifying aspects with regards to previous literature: it adds other different ethnic ancestries of patients, points out a morphological analysis of autopsy material with unchanged structures in the brain, liver and kidneys and marks in the patient VT a dissociation between a symptom-free clinical pattern since age 7 and the persistent biochemical abnormality until the present age, 15 years. The knowledge of the existence of these diseases in our country together with the availability and access to GC/MS of high precision and speed, will allow early diagnosis and better therapeutic results.

Sandhoff disease in Argentina: high frequency of a splice site mutation in the HEXB gene and correlation between enzyme and DNA-based tests for heterozygote detection.

The level of beta-hexosaminidase activity in plasma and leukocytes and the frequency of three known HEXB mutations were studied in an Argentinean deme with high incidence of infantile Sandhoff disease. Two mutations were previously identified in one of two Sandhoff patients from the region, a splice mutation, IVS-2 + 1 G-->A, and a 4-bp deletion, delta CTTT782-785. These mutations, and a 16-kb deletion from the 5' end of the HEXB gene common in non-Argentineans, were screened in 9 Sandhoff patients (all unrelated), 24 obligate heterozygotes, 33 additional individuals belonging to families with affected members, and 64 randomly ascertained individuals from the high risk region. Of 31 independent alleles examined, including those of the two patients previously reported, 30 had the IVS-2 splice mutation and only the originally reported patient had the delta CTTT deletion. The 16-kb deletion was not observed. Further, among the 57 unaffected members of families with a previous history of Sandhoff disease, and absolute correlation was found between carrier diagnosis by enzyme assay of leukocytes and the DNA-based tests for mutation. One of the 64 controls was classified as a carrier by enzyme assay but did not have one of the three mutations screened. We conclude that a single mutation predominates in this Argentinean population and that the DNA-based test can be an effective supplement or alternative to enzyme-based testing.

Characterization of two HEXB gene mutations in Argentinean patients with Sandhoff disease.

Beta-hexosaminidase A (beta-N-acetyl-D-hexosaminidase, EC 3.2.1.5.2) is a lysosomal hydrolase composed of an alpha- and a beta-subunit. It is responsible for the degradation of GM2 ganglioside. Mutations in the HEXB gene encoded beta-subunit cause a form of GM2 gangliosidosis known as Sandhoff disease. Although this is a rare disease in the general population, several geographically isolated groups have a high carrier frequency. Most notably, a 1 in 16-29 carrier frequency has been reported for an Argentinean population living in an area contained within a 375-km radius from Córdoba. Analysis of the genomic DNA of two patients from this region revealed that one was homozygous for a G to A substitution at the 5' donor splice site of intron 2. This mutation completely abolishes normal mRNA splicing. The other patient was a compared of the intron 2 G-->A substitution and a second allele due to a 4-bp deletion in exon 7. The beta-subunit mRNA of this allele is unstable, presumably as a result of an early stop codon introduced by the deletion. Two novel PCR-based assays were developed to detect these mutations. We suggest that one of these assays could be modified and used as a rapid screening procedure for 5' donor splice site defects in other genes. These results provide a further example of the genetic heterogeneity that can exist even in a small geographically isolated population.

Mucopolysaccharidosis type VII (beta-glucuronidase deficiency): a chronic variant with an oligosymptomatic severe skeletal dysplasia.

We report on a 20-year-old male with a beta-glucuronidase (GUSB) deficiency mucopolysaccharidosis. He had pectus carinatum, gross thoracic kyphoscoliosis, and hip dysplasia, a picture which became conspicuous after age 4 years. Hepatosplenomegaly, herniae, corneal clouding, and neurological abnormalities were absent. Although he had Alder-type granulations in his polymorphonuclear leukocytes, the urine did not contain a significant excess of mucopolysaccharides. Electron microscopic examination of skin and gingival biopsies, leukocytes, and cultured skin fibroblasts showed numerous single membrane-limited vacuoles either empty or filled with fibrillogranular material; this last tissue did not contain metachromatic granules. Radiographs demonstrated a distinct spondyloepiphyseal dysplasia in which the most striking changes were confined to the thoracic spine (flattening and collapse in T7, T8 and T10 vertebral bodies) and to the femoral capital epiphyses (irregularities and fragmentation). The activity of GUSB in the patient's serum, leukocytes, and fibroblasts was severely decreased; the GUSB activity in the serum and leukocytes from the parents and 2 asymptomatic sibs was subnormal. Immunoblot analysis showed very low levels of cross-reactive material towards anti-GUSB antiserum in the patient's leukocyte and fibroblast extracts. This patient was more severely affected in his skeleton than other described patients with an oligosymptomatic chronic form. This case broadens the clinical and biochemical picture associated with GUSB deficiency and may represent a new variant of the disease.

[Hepatic glycogen synthetase deficiency or glycogen storage disease-zero. Mild phenotype with partial enzymatic defect]. / Deficiencia en glucógeno sintetasa hepática o glucogenosis tipo cero. Fenotipo menos severo con defecto enzimático parcial.

Since the original description 26 years ago, of the hepatic glycogen synthetase deficiency, only one more case was reported in 1977. We present the studies carried out on an Argentine boy of Italian ancestry who at age 21 months, showed signs of hepatic deficiency with mild clinical symptoms which contrasted with a remarkable fatty liver degeneration. A totally atypic reaction to fructose overload (Table 1, Fig. 1) was the first key to the diagnosis. Glucose levels were not significantly modified by glucagon after 12-hours fasting, but it did increase the glycemia, with decrease of lactate and alanine 3 hours after-meal (Fig. 2a, b). The 24-hours metabolic profile showed fasting hypoglycemia, hyperketonemia, low alanine concentrations and mild lactatemia and hyperglycemia and a net post-prandial increase of lactate (Fig. 3). This profile when reduced to 14 hours, 12-fasting hours and 2-postprandial hours (Fig. 4), revealed similar alterations in an asymptomatic younger brother. The development of the investigation led to a second hepatic biopsy which confirmed hepatic steatosis and to an ultrastructural study, which showed subcellular alterations in the liver and also in muscle (Fig. 5). Moreover low content of hepatic glycogen was observed along with glycogen synthetase activity between 20-25% that of controls, being normal the enzyme activity in muscle and fibroblasts cultured from a skin biopsy (Table 2). The clinical pattern mainly without hypoglycemia, convulsions and/or mental retardation and a normal height and body mass development, allowed us to postulate that this Argentine report would be a mild variant of the disease formerly described and would be correlated with a partial deficiency of the hepatic glycogen synthetase.

Deficiencia en glucógeno sintetasa hepática o glucogenosis tipo cero. Fenotipo menos severo con defecto enzimático parcial. / [Hepatic glycogen synthetase deficiency or glycogen storage disease-zero. Mild phenotype with partial enzymatic defect]

Since the original description 26 years ago, of the hepatic glycogen synthetase deficiency, only one more case was reported in 1977. We present the studies carried out on an Argentine boy of Italian ancestry who at age 21 months, showed signs of hepatic deficiency with mild clinical symptoms which contrasted with a remarkable fatty liver degeneration. A totally atypic reaction to fructose overload (Table 1, Fig. 1) was the first key to the diagnosis. Glucose levels were not significantly modified by glucagon after 12-hours fasting, but it did increase the glycemia, with decrease of lactate and alanine 3 hours after-meal (Fig. 2a, b). The 24-hours metabolic profile showed fasting hypoglycemia, hyperketonemia, low alanine concentrations and mild lactatemia and hyperglycemia and a net post-prandial increase of lactate (Fig. 3). This profile when reduced to 14 hours, 12-fasting hours and 2-postprandial hours (Fig. 4), revealed similar alterations in an asymptomatic younger brother. The development of the investigation led to a second hepatic biopsy which confirmed hepatic steatosis and to an ultrastructural study, which showed subcellular alterations in the liver and also in muscle (Fig. 5). Moreover low content of hepatic glycogen was observed along with glycogen synthetase activity between 20-25

that of controls, being normal the enzyme activity in muscle and fibroblasts cultured from a skin biopsy (Table 2). The clinical pattern mainly without hypoglycemia, convulsions and/or mental retardation and a normal height and body mass development, allowed us to postulate that this Argentine report would be a mild variant of the disease formerly described and would be correlated with a partial deficiency of the hepatic glycogen synthetase.

Diagnosis and characterization of GM 2 gangliosidosis type II (Sandhoff disease) by analysis of the accumulating N-acetyl-glucosaminyl oligosaccharides with high performance liquid chromatography.

The N-acetyl-glucosaminyl oligosaccharides excreted in urine and accumulating in tissues of Sandhoff disease patients have been analyzed and characterized using a combination of high performance liquid chromatography and 500 MHz proton magnetic resonance spectroscopy. Delineation between infantile and juvenile onset forms of the disease was possible, as the latter forms had 6- to 13-fold lower levels of urinary oligosaccharides. Patients from a geographically isolated population deme in the La Rioja region of Argentina had urinary oligosaccharides similar to unrelated non-Argentinean patients with identical clinical phenotype. Together, these results indicate that the urinary oligosaccharides serve as useful indicators of the mutation differences or clinical heterogeneity within this disease only in cases of markedly differing clinical presentation. Analysis of the accumulating metabolites in liver, kidney, pancreas, lung and spleen, showed a similar oligosaccharide pattern which differed dramatically from brain. These results suggest the possibility of tissue specific regulation of oligosaccharide biosynthesis since there are notable differences between neural and visceral tissues.