First-trimester diagnosis of maple syrup urine disease on intact chorionic villi

Hypoglycemia in association with various organic and amino acid disorders

A number of organic and amino acidemias, particularly those that involve the oxidation of fatty acids, cause hypoglycemia intermittently. This may be associated with distrubances of acid base equilibrium and accumulation of lactic acid and/or ketone bodies. When such diseases are not diagnosed rapidly, they might lead to neurological crippling and, at times, death. As a group, these disorders involve more than 1 organ and their phenotypic expression may include all or a single system. The symptoms may appear soon after birth or as late as 1 year of age. Their early recognition and rapid intervention provide rewarding clinical outcome. With the recent advances in diagnostic techniques, such as the introduction of tandem mass spectrometry (MS), screening for these diseases now can be performed because rapid identification on a large scale is possible. The phenotypes, mutations involved, pathognomonic laboratory findings, prognosis, and treatment procedures available have been reviewed for major diseases.

A case of maple syrup urine disease misdiagnosed as tetanus neonatorum on admission

A case of Maple Syrup Urine Disease (MSUD) is presented with clinical signs and symptoms on admission resembling neonatal tetanus. Diagnosis had to be differentiated between MSUD and other metabolic disorders and neonatal infections (especially neonatal tetanus because of severe opisthotonos) and generalized seizures of the patient. Early diagnosis of the MSUD patient is very important for effective therapy and better long-term prognosis as well as genetic counselling and prenatal diagnosis for future pregnancies.

Fetal diagnosis of inborn errors of metabolism

Nearly 4000 different human disorders are supposed or known to be due to a single gene mutation. In about 10%, an early diagnosis is possible by the demonstration of specific abnormalities of metabolites in blood and/or urine, an abnormal structure/function of a particular (enzyme) protein or by the (in)direct demonstration of the gene mutation using DNA analysis. These methods of molecular analysis can often also be used for carrier detection. Early identification of couples at risk of handicapped offspring followed by genetic counselling forms the basis for prevention. Follow-up studies have shown that more than half of the couples at risk of a child with a genetic disease refrain from pregnancy. An important alternative for couples at risk is prenatal monitoring and selective abortion. During the last 10-15 years, the technology of fetal diagnosis of genetic diseases has improved and the number of Mendelian disorders that can be diagnosed in utero has increased to more than 100. In the second-trimester of pregnancy, about two dozen inborn errors of metabolism have been diagnosed by metabolite analysis of amniotic fluid supernatant using gas chromatography-mass spectrometry or electrophoretic methods. About 5000 pregnancies at risk of different types of haemoglobinopathy, haemophilia, alpha-1-antitrypsin deficiency and a few other diseases not expressed in amniotic fluid cells have been investigated by biochemical analysis after fetal blood sampling. The most common approach towards fetal diagnosis of inborn errors of metabolism has been the demonstration of a specific enzyme deficiency in cultured amniotic fluid cells. In this way some 60 different diseases have been diagnosed, usually after 2-4 weeks of cultivation after amniocentesis at 16 weeks gestation. In addition, some 20 other Mendelian disorders have been diagnosed in utero by ultrasonography and non-biochemical analysis of amniotic fluid cells or fetal skin biopsies. The introduction of chorionic villus sampling has offered the possibility of first-trimester fetal diagnosis of a large number of Mendelian disorders. The overall diagnostic experience until mid-1986 amounts to about 1500 pregnancies at risk. Some 45 different inborn errors have been diagnosed by enzyme assays directly on chorionic villus homogenate or after incubation with radiolabelled precursors of intact villi followed by chromatography or other types of analysis. In a few instances, cell cultivation for a period of 2-3 weeks is required to establish a reliable biochemical diagnosis.