Kirsten Wølch Rasmussen

Biochemical studies in a patient with defects in the metabolism of acyl-CoA and sarcosine: Another possible case of glutaric aciduria type II

The clinical and biochemical abnormalities in a neonate, who died in coma accompanied by severe hypoglycaemia at the age of 3 days, are described. The study of the urinary metabolic profiles of organic acids and amino acids revealed that the excretion rates of glutaric acid, isovaleric acid, isovalerylglycine, 3-hydroxyisovaleric acid and isobutyric acid were very high. Increased excretion rates were also found for 2-methylbutyric acid, adipic acid, caproylglycine, 5-hydroxycaproic acid, caproic acid and butyric acid. The amino acid, sarcosine, was excreted in enhanced amounts and the patient had lactic aciduria, whereas the excretion of 3-hydroxybutyric acid was only moderately increased. This abnormal excretion pattern is consistent with a defect in the metabolism of acyl-CoAs and sarcosine. Normal activity of glutaryl-CoA dehydrogenase was found, excluding glutaryl-CoA dehydrogenase deficiency (glutaric aciduria type I).

An excess of chromosome 1 breakpoints in male infertility.

In a search for potential infertility loci, which might be revealed by clustering of chromosomal breakpoints, we compiled 464 infertile males with a balanced rearrangement from Mendelian Cytogenetics Network database (MCNdb) and compared their karyotypes with those of a Danish nation-wide cohort. We excluded Robertsonian translocations, rearrangements involving sex chromosomes and common variants. We identified 10 autosomal bands, five of which were on chromosome 1, with a large excess of breakpoints in the infertility group. Some of these could potentially harbour a male-specific infertility locus. However, a general excess of breakpoints almost everywhere on chromosome 1 was observed among the infertile males: 26.5 versus 14.5% in the cohort. This excess was observed both for translocation and inversion carriers, especially pericentric inversions, both for published and unpublished cases, and was significantly associated with azoospermia. The largest number of breakpoints was reported in 1q21; FISH mapping of four of these breakpoints revealed that they did not involve the same region at the molecular level. We suggest that chromosome 1 harbours a critical domain whose integrity is essential for male fertility.

Glutaric aciduria in progressive choreo‐athetosis

The clinical symptoms in a 10‐year‐old girl with progressive dystonic cerebral palsy are described. The biochemical findings were dominated by large amounts of glutaric acid in the urine. The disorder is caused by impairment of the degradation of glutaryl‐CoA.

Systematic re-examination of carriers of balanced reciprocal translocations : a strategy to search for candidate regions for common and complex diseases

Balanced reciprocal translocations associated with genetic disorders have facilitated the identification of a variety of genes for early-onset monogenic disorders, but only rarely the genes associated with common and complex disorders. To assess the potential of chromosomal breakpoints associated with common/ complex disorders, we investigated the full spectrum of diseases in 731 carriers of balanced reciprocal translocations without known early-onset disorders in a nation-wide questionnaire-based re-examination. In 42 families, one of the breakpoints at the cytogenetic level concurred with known linkage data and/or the translocation co-segregated with the reported phenotype, for example, we found a significant linkage (lod score=2.1) of dyslexia and a co-segregating translocation with a breakpoint in a previously confirmed locus for dyslexia. Furthermore, we identified 441 instances of at least two unrelated carriers with concordant breakpoints and traits. If applied to other populations, re-examination of translocation carriers may identify additional genotype–phenotype associations, some of which may be novel and others that may coincide with and provide additional support of data presented here.

Application of fluorescence in situ hybridization techniques in clinical genetics use of two alphoid repeat probes detecting the centromeres of chromosomes 13 and 21 or chromosomes 14 and 22 respectively

Two cloned DNA fragments, one derived from an alpha satellite subfamily common to chromosomes 13 and 21, and the other derived from a similar subfamily common to chromosomes 14 and 22, have been used as biotinylated probes in in situ hybridization studies. Under high stringency conditions, chromosome specific centromeric labelling can be obtained. The applications of this technique in clinical situations are illustrated on metaphases from a fetus with trisomy 21, a fetus with trisomy 13, and a child with clinical features of cat‐eye syndrome.

HEREDITARY BILATERAL RETINOBLASTOMA, PINEALOMA AND NORMAL CHROMOSOMES

We report a boy with bilateral, familial retinoblastoma recognized at the age of 3 months. At the age of 2 1/2 years the patient developed a tumour in the pineal region. Both tumours were successfully treated by radiation. The chromosomes were normal when examined by the prophase technique, in particular there was no deletion of band q 14 of chromosome 13. We consider the simultaneous occurrence of retinoblastoma and pinealoma as more then a pure coincidence, probably a consequence of a generally increased susceptibility to cancer and of the histogenetic similarities of retina and pineal body.

In situ hybridization analysis of isodicentric X-chromosomes with short arm fusion.

We present here an alternative approach to the study of mosaic cell lines containing dicentric chromosomes. The approach is based on chromosome‐specific non‐radioactive in situ hybridization with centromere (alpha satellite DNA) probes. The hybridization analysis may be used as an alternative to the C‐band analysis, while at the same time to some extent replacing the Q‐band analysis as well. The advantage of using in situ hybridization is mainly that it allows the very fast screening of a large number of metaphases. We illustrate this new application of the technique by using it for the analysis of two cases of isodicentric X‐chromosomes. The approach is expected to be generally applicable, so that it may be applied to the scoring of other types of chromosomal mosaicism as well.

Excretion pattern of branched-chain amino acid metabolites during the course of acute infections in a patient with methylmalonic acidaemia.

A 1-year-old boy with a typical B12-responsive form of methylmalonic acidaemia was hospitalized twice due to acute bacterial infections. On both occasions, the child was lethargic with a severe ketoacidosis on admission. Intensive therapy with protein restriction, intravenous administration of electrolytes and antibiotics was effective within 4 days on both occasions. The urinary excretion of organic acids showed the same pattern on both occasions. There were rising excretion concentrations, reaching a peak value within the first 24-hour period, for the following compounds: 3-hydroxybutyric acid, 3-hydroxypropionic acid, 3-hydroxyisobutyric acid and 3-hydroxyisovaleric acid. Excretion concentrations of the following rose for 48 h: isobutyric acid, 2-methylbutyric acid, isovaleric acid, lactic acid and the 2-oxo-acids.There was no increase until 12–24 h after the onset of severe illness in the excretion of propionic acid and methylmalonic acid. Propionic acid excretion was maximal at about 48 h, while peak excretion of methylmalonic acid was delayed until about 72 h after the onset of severe illness; at this time there was clinical improvement. The biochemical implications of this excretion pattern are discussed.

Glutaric aciduria in two brothers.

Case 1 (M.H.) The patient, whose parents are first cousins, was born at term after a normal pregnancy (birth weight 3400g). He was normal in the neonatal period, but at two years he could hardly walk and had a mild cerebellar ata_,da. Later, involuntary movements increased and at nine years of age presented as choreiform, fast-repeated, shifting hyperkinetic movements. His speech was moderately dysarthric, but he was mentally normal and was doing well at school.

De novo KAT6B Mutation Identified with Whole-Exome Sequencing in a Girl with Say-Barber/Biesecker/Young-Simpson Syndrome

Say-Barber/Biesecker/Young-Simpson syndrome (SBBYSS; OMIM 603736) is a rare syndrome with multiple congenital anomalies/malformations. The clinical diagnosis is usually based on a phenotype with a mask-like face and severe blepharophimosis and ptosis as well as other distinctive facial traits. We present a girl with dysmorphic features, an atrial septal defect, and developmental delay. Previous genetic testing (array-CGH, 22q11 deletion, PTPN11 and MLL2 mutation analysis) gave normal results. We performed whole-exome sequencing (WES) and identified a heterozygous nonsense mutation in the KAT6B gene, NM_001256468.1: c.4943C>G (p.S1648*). The mutation led to a premature stop codon and occurred de novo. KAT6B sequence variants have previously been identified in patients with SBBYSS, and the phenotype of the girl is similar to other patients diagnosed with SBBYSS. This case report provides additional evidence for the correlation between the KAT6B mutation and SBBYSS. If a patient is suspected of having a blepharophimosis syndrome or SBBYSS, we recommend sequencing the KAT6B gene. This is a further example showing that WES can assist diagnosis.