Rett syndrome revisited: a patient with biotin dependency

Analytical techniques for determining biotin

Biotin is a vitamin of the B-complex, which plays an important biochemical role in every living cell. In the recent years, the interest in this vitamin has been rekindled, mainly due to its association with serious human disorders, such as the inherited syndrome multiple carboxylase deficiency, which can be successfully treated with biotin administration. Diagnosis of biotin deficiency as well as monitoring of biotin levels in biological fluids of patients receiving biotin treatment is crucial. Equally important is the determination of biotin levels in pharmaceutical preparations as well as in food and food supplement products, which constitute the main source of biotin in humans. Several analytical methods for measuring biotin in various samples, e.g. human fluids, pharmaceutical formulations, food material etc., have been reported in the literature. In this review, the most representative of these methods are presented, and their characteristics are evaluated.

The effects of biotin deficiency on organic acid metabolism: increase in propionyl coenzyme A-related organic acids in biotin-deficient rats

Volatile organic acid levels in plasma and tissues and nonvolatile organic acid levels in urine of biotin-deficient (BD) rats were measured and compared with other factors of biotin deficiency. Biotin levels and the activities of propionyl coenzyme A (CoA) carboxylase (PCC) in the livers of these rats were decreased, respectively, to 22% +/- 3% and 3.6% +/- 0.3% of the average values of pair-fed controls. Plasma concentrations of propionate were higher (15 to 223 micrograms/mL) than those of controls (5 to 7 micrograms/mL), whereas plasma levels of 3-methylcrotonate were only minimally increased as compared with those of controls. Concentrations of these volatile acids in the tissues were similarly increased, although those in brain showed less remarkable increases as compared with levels in other tissues. In the urine of BD rats, large amounts of organic acids derived from propionyl CoA, as well as those from 3-methylcrotonyl CoA, were excreted. Plasma propionate levels were not apparently related to the severity of clinical symptoms, biotin levels, or carboxylase activities, but were related to the amounts of urinary ketone bodies, lactate, and some of the organic acids derived from branched-chain amino acids, including those from propionyl CoA.

A case of the Rett syndrome with acute encephalopathy induced during calcium hopantenate treatment

We report a girl with the Rett syndrome who had acute encephalopathy probably induced by calcium hopantenate (HOPA). This 4-year-6-month-old girl had a history of moderate developmental delay and had received HOPA administration when first admitted at 2 years 6 months of age with hypoglycemia, hyperammonemia, lactic and pyruvic acidemia, and non-ketotic dicarboxylic aciduria. After this episode, she showed the rapid destructive stage of the Rett syndrome, i.e., severe psychomotor retardation with loss of speech, peculiar stereotypic hand movements, autistic behavior and seizures. Despite subsequent investigations, including analysis of urinary metabolites of organic and amino acids, measurement of serum carnitine and a muscle biopsy, we could not clarify the primary metabolic abnormalities in this girl.

Hair copper and zinc concentrations in the Rett syndrome

The hair copper and zinc concentrations in patients with the Rett syndrome in 9 hospitals or institutions, and female age-matched controls were investigated. The copper and zinc concentrations in the 23 patients were 15.1 +/- 3.6 and 177 +/- 20 micrograms/g dry weight (mean +/- SD), respectively, and those in the 22 controls were 14.7 +/- 3.4 and 181 +/- 22, respectively. No significant differences were detected between the copper or zinc concentrations in the patients and controls. The copper and zinc concentrations did not change with age, or the hospital or institution. The ratio of the copper and zinc concentrations was also constant. We conclude that the hair copper and zinc concentrations in patients with the Rett syndrome are the same as those in controls.

Rett syndrome: review and discussion of current diagnostic criteria

Rett syndrome is a mental retardation syndrome that occurs only in females and consists of normal pre-, peri-, and neonatal growth and development. It is followed by rapid neurobehavioral deterioration in late infancy or early childhood, a developmental arrest, plateauing, and then either a course of retarded development or continued deterioration. The period of rapid neuro-behavioral deterioration manifests as a partial autistic syndrome, with loss of production and comprehension of language, hyperactivity, hyperventilation, hand-wringing, and ataxic gait. Current diagnostic criteria are discussed and suggestions for further research are presented.

The biochemical basis of mitochondrial diseases

Dysfunctioning of human mitochondria is found in a rapidly increasing number of patients. The mitochondrial system for energy transduction is very vulnerable to damage by genetic and environmental factors. A primary mitochondrial disease is caused by a genetic defect in a mitochondrial enzyme or translocator. More than 60 mitochondrial enzyme deficiencies have been reported. Secondary mitochondrial defects are caused by lack of compounds to enable a proper mitochondrial function or by inhibition of that function. This may result from malnutrition, circulatory or hormonal disturbances, viral infection, poisoning, or an extramitochondrial error of metabolism. Once mitochondrial ATP synthesis decreases, secondary mitochondrial lesions may be generated further, due to changes in synthesis and degradation of mitochondrial phospholipids and proteins, to mitochondrial antibody formation following massive degradation, to accumulation of toxic products as excess acyl-CoA, to the depletion of Krebs cycle intermediates, and to the increase of free radical formation and lipid peroxidation.

Research on Rett syndrome: strategy and preliminary results

The research strategy presented here involves four assumptions: (1) Rett syndrome exists; (2) a single cause will eventually be found to account for the majority of cases presently assigned to this disease category; (3) it is genetically determined; and (4) it represents a neurodegenerative disorder that can be defined by quantitative studies of nervous system structure and function. The strategy proposed here involves the comprehensive study of 100 patients with the classic Rett syndrome phenotype. Studies include the (1) search for a diagnostic marker; (2) high-resolution cytogenetic banding techniques, (3) quantitative morphologic studies of postmortem brain tissue as well as neurochemical analyses including autoradiographic techniques, radioimmunoassays, and in situ hybridization; and (4) positron emission tomography studies of cerebral glucose metabolism and neurotransmitters.

Rett syndrome--a review and discussion of syndrome delineation and syndrome definition

The current status of clinical genetic and pathogenetic knowledge in Rett syndrome is reviewed and updated. Some of the concepts which are highlighted include among others, casual homogeneity vs heterogeneity; the difficulty of dealing with potential variability while the possibility of heterogeneity still exists; progress in examining genetic hypotheses. We review our experience with 8 new patients, note the evidence for the presence of congenital hypotonia in all and several instances of minor anomalies and again raise the issue of whether girls with the Rett syndrome are in fact normal from the time of birth and in early infancy until the characteristic phenotype is recognizable. Previous recommendations for standardized international history, examination and investigation protocols are strongly reinforced, and the question as to who should study brains of Rett syndrome patients is raised by a parent. As is the case in most conditions now being studied by molecular geneticists, finding a marker will be a major etiologic breakthrough, but the work of delineating the pathogenesis will remain to be done.