Adrenoleukodystrophy: diagnosis and carrier detection by determination of long-chain fatty acids in cultured fibroblasts

Linkage analysis in X-linked adrenoleukodystrophy and application in post- and prenatal diagnosis

We have performed linkage analysis with the DNA markers DXS52 and the clotting factor VIII gene (F8C), in several large families with X-linked adrenoleukodystrophy (ALD). The tight linkage to DXS52 could be extended giving a maximal LOD score of 22.5 at 1 cM. F8C was also tightly linked to ALD with a maximal LOD score of 7.8 without recombination. Multipoint linkage analysis with the markers DXS304, DXS52, and F8C indicated that both the gene for ALD and for F8C are distal to DXS52. In four patients with ALD, no major structural rearrangement in the Xqter region was observed; in particular, there were no abnormalities in the vision blindness genes. DNA analysis appeared to be of use in determination of the carrier status of females at risk, for the determination of the origin of the mutation in a particular family, and for prenatal diagnosis.

Prenatal and perinatal diagnosis of peroxisomal disorders

Peroxisomes play an essential role in human cellular metabolism. Peroxisomal disorders, a group of genetic diseases caused by peroxisomal dysfunction, can be classified into three groups: (1) disorders of peroxisome biogenesis with a generalized loss of peroxisomal functions (Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum disease, hyperpipecolic acidaemia); (2) disorders with a loss of multiple peroxisomal functions (rhizomelic chondrodysplasia punctata and Zellweger-like syndrome; (3) disorders with loss of a single peroxisomal function (X-linked adrenoleukodystrophy, peroxisomal thiolase deficiency, bifunctional protein deficiency, acyl-CoA oxidase deficiency, classic Refsum disease, hyperoxaluria type I and acatalasaemia). Prenatal diagnosis is indicated in all these genetic disorders with the exception of classic Refsum disease, most types of hyperoxaluria type I and acatalasaemia. A variety of techniques is available now for the prenatal diagnosis of peroxisomal disorders in the first or second trimester of gestation. Prenatal diagnosis was performed by us in 70 pregnancies at risk for a disorder of peroxisome biogenesis, three for rhizomelic chondrodysplasia punctata, four for X-linked adrenoleukodystrophy and two for a defect in peroxisomal beta-oxidation. Fourteen affected fetuses were identified; no false negative cases were obtained.

Carrier detection for adrenoleukodystrophy by high-performance liquid chromatography

With a newly devised method of high-performance liquid chromatography (HPLC), we scrutinized lipid extraction of very-long-chain fatty acids of cultured skin fibroblasts from obligate (n = 4) and possible (n = 3) carriers for adrenoleukodystrophy (ALD) in order to establish the best method to detect a carrier for the ALD gene. All four methods (total esterified fatty acids, total fatty acids with acetonitrile-HCl, total fatty acids with methanolic-HCl, and triacylglycerol fraction) were applicable to carrier detection, but from the standpoint of simplicity and sensitivity, the method using total fatty acids with acetonitrile-HCl seemed to be the best. This is the first study of ALD carrier detection in which cultured skin fibroblasts are investigated using HPLC as an analytical method.

Adrenoleukodystrophy in an adult female. A clinical, morphological, and neurochemical study

A 43-year-old female with adrenoleukodystrophy (ALD) is described, who developed spastic tetraparesis, suffered grand mal seizures, and became stuporous and demented during the last 5 years of her life. Computed tomography revealed symmetrical hypodense lesions in the peritrigonal regions. Adrenal insufficiency was not evident except for skin pigmentation. The ultrastructure of a rectal biopsy specimen showed inclusions with lamellae and interspersed clefts in macrophages of the submucosal layer. At autopsy, the adrenals were found to contain large foam cells filled with similar inclusions. The brain cortex and the spinal cord were histologically normal. However, cerebral white matter exhibited widespread demyelination which spared only the arcuate fibres. In regions of less severe demyelination scattered inflammatory cells were seen. On electron microscopy, aggregates of typical paired leaflets with distinct intermediate lines were demonstrated in perivascular macrophages. Histochemical study showed these cells to contain free as well as esterified cholesterol. Gas chromatographic analysis of very long chain fatty acids (VLFA) from the demyelinated cerebral white matter showed a marked increase of C26:0 fatty acid in cholesterol esters and above-normal values for C24:0 and C24:1 in gangliosides. It is suggested that the condition was a heterozygote form of X-linked ALD. Patients with neurodegenerative symptoms with or without adrenal insufficiency can easily be screened for X-linked ALD by VLFA analysis in blood or cultured fibroblasts.

Disturbed very long chain (C24-C26) fatty acid pattern in fibroblasts of patients with Zellweger's syndrome

The very long chain fatty acids in cultured fibroblasts from six patients with the cerebro-hepato-renal syndrome of Zellweger, from six of their parents, from three controls, and also in three amniotic fluid control cell lines were analysed by gas chromatography. Increased concentrations of hexacosanoic acid (C26:O) were consistently found in the Zellweger syndrome. Also the ratios C26:O/C22:O, C25:O/C22:O, and C24:O/C22:O were elevated. The very long chain fatty acid levels and ratios in fibroblasts from the patients' parents were within the normal range. Findings in amniotic fluid cell lines indicate the possibility of antenatal diagnosis for Zellweger's syndrome. The similarities between neonatal adrenoleukodystrophy and Zellweger's syndrome suggest the applicability of this technique also in neonatal adrenoleukodystrophy.