Anderson-Fabry disease--family linkage studies using two polymorphic X-linked DNA probes.

Anderson-Fabry disease is an X-linked lysosomal storage disorder due to alpha-galactosidase A deficiency. In affected males there is a high mortality in early adult life due to renal failure and cardiovascular complications. We describe our preliminary results from genetic linkage studies in five families using two polymorphic DNA probes, DXS17 and DXYS1, mapping to an area on the long arm of the X chromosome between Xq13-22. DXS17 identified a Taql polymorphism closely linked to the disease locus in three families (lodmax Z = 4.23. at a recombination fraction decreases theta = 0.0). Restriction fragment length polymorphisms detected by DXYS1 were not linked.

Review: genetics of steroid sulphatase deficiency and X-linked ichthyosis.

Steroid sulphatase deficiency which started out as a curious placental microsomal enzyme deficiency associated with low maternal urinary oestrogen excretion and difficulties in delivery, first described only twelve years ago, has now become a generalized enzyme deficiency associated also with a common skin disease. It turns out not only to be inherited in an X-linked recessive manner, but to be part of a gene cluster which includes the Xg blood group gene and which has been precisely assigned to the distal tip of the short arm of the X-chromosome. This cluster is unique for genes on the X-chromosome in escaping X-inactivation. It remains to be unequivocally demonstrated whether steroid sulphatase is identical to arylsulphatase C or whether these are two enzymes sharing a common polypeptide chain determined by a single gene. However, Rose (1982) presents evidence that one steroid sulphatase is probably identical with arylsulphatase C. It also remains to be conclusively demonstrated whether the gene for the enzyme deficiency is also that for ichthyosis or whether they are two very closely linked genes. If the former is true the role of steroid sulphatase in the abnormal keratinization of ichthyosis is still to be elucidated. Above all the special nature of the DNA in this unique region awaits description.

Congenital haemolytic anaemia resulting from glucose phosphate isomerase deficiency: genetics, clinical picture, and prenatal diagnosis.

Glucose phosphate isomerase (GPI) deficiency with severe haemolysis and hydrops fetalis was found in the first child of unrelated, healthy Caucasian parents. The child died at 3 hours. Both parents were found to have 50% of normal red cell GPI activity and qualitative tests on their red cells and white cells showed that each was heterozygous for a different GPI variant allele associated with enzyme deficiency. Tests on the placenta showed that the propositus was a 'compound' heterozygote. Examination of amniotic cells obtained by amniocentesis on the mother at 28 weeks in her second pregnancy led to the prenatal diagnosis of GPI deficiency. This second child, a 'compound' heterozygote at the GPI locus indistinguishable from the first, was successfully treated by immediate exchange transfusion and subsequent blood transfusions.