Interstitial deletions without phenotypic effect: prenatal diagnosis of a new family and brief review.

A 39-year-old woman (G4P1SAB2) was referred for amniocentesis for advanced maternal age. An interstitial deletion of the G-dark band 11p12 was found in the fetus. Blood from the mother and her previous son was cultured and the same deletion was found in both. The absence of phenotypic effect in this family further confirms that G-dark euchromatic deletions are compatible with a normal phenotype, and underlines the importance of checking familial karyotypes even when apparently unbalanced structural rearrangements are found at prenatal diagnosis.

Investigation of three patients with the "ring syndrome", including familial transmission of ring 5, and estimation of reproductive risks.

We report three cases of ring chromosome 5 [r(5)], two familial (mother and daughter) and one sporadic. The phenotype resembled that of the "ring syndrome" with prenatal onset of short stature, growth retardation, mild facial dysmorphism and normal psychomotor development. Extended metaphase and prometaphase chromosome preparations using G-, R- and Q-banding and scanning electron microscopy (SEM) failed to demonstrate deletion in the ring 5. Flow karyotype using the FACS cell sorter and peak area analysis showed the r(5) to be in the same position as the normal chromosome 5. The deletion that is presumably associated with ring formation appears to involve less that one megabase of DNA. In the "complex" rings, high resolution SEM showed fragile sites at the 5q34 and 5q35 region with frequent deletions at that site. A literature survey suggests that when a parent carries a ring chromosome about 80% of recognised pregnancies result in live birth. Of these, about half have a normal phenotype and karyotype, and half inherit the parental ring; about half of those acquiring the ring (20%) show significant mental retardation.

A further family with congenital renal proximal tubular dysgenesis.

A new syndrome of oligohydramnios, Potter's syndrome, and anuric renal failure leading to stillbirth or neonatal death from respiratory failure has recently been described. Histologically, there is renal tubular dysgenesis, especially of the proximal tubules, and apparent glomerular crowding. To date, five families have been reported, in four of which there have been affected sibs and in two parental consanguinity. The disorder is, therefore, thought to be inherited in an autosomal recessive manner.

The neurological complications of Anderson-Fabry disease (alpha-galactosidase A deficiency)--investigation of symptomatic and presymptomatic patients.

Anderson-Fabry disease is an X-linked inborn error of metabolism characterized by subnormal activity of the lysosomal hydrolase, alpha-galactosidase A. We have assessed the incidence and nature of neuropathy in 12 patients (seven affected men and five carrier females). Abnormalities of cutaneous thermal sensation were common, even in asymptomatic carriers, with a unique predilection for cold sensitivity which suggests involvement of small myelinated nerve fibres. Intracranial abnormalities were frequently detected by magnetic resonance imaging (MRI) in males, both with and without overt cerebrovascular disease, and were more extensive in older patients. Such abnormalities were not detected in carriers. Auditory and vestibular abnormalities were present in six patients, only one of whom was symptomatic. Cranial MRI and assessment of cutaneous thermal thresholds are sensitive techniques which can identify neurological involvement in asymptomatic patients. They may be of benefit in monitoring the effectiveness of enzyme replacement therapy and excluding the carrier state for the defective gene.

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.

Ethical guidelines in fetal medicine.

The ethical guidelines in the clinical practice of fetal medicine are discussed, largely from the point of view of early prenatal diagnosis. The discussion concentrates on several specific aspects including counselling, good procedure, prenatal screening, disclosure of results including fetal sex, experimentation and assessment of new technologies and health education. The emphasis is placed on the importance of informed consent, choice and understanding on the part of the patient, and the professional competence of the doctor and other professionals she may meet.

First-trimester diagnosis of Lesch-Nyhan syndrome.

Chorionic villi were sampled at 8-9 weeks' gestation in four women whose fetuses were at risk for Lesch-Nyhan syndrome. Radiochemical assay of hypoxanthine phosphoribosyl transferase activity and fetal sexing (in two fetuses by means of a Y chromosome specific cDNA probe) showed that three fetuses were affected. The biochemical findings were confirmed after therapeutic abortion in two cases and spontaneous abortion in the third. Chorion biopsy and ultramicroscale enzymology may be a suitable alternative to recombinant-DNA-based methods for first-trimester diagnosis in selected diseases where the abnormal gene product is an enzyme expressed in the chorion by the 8th week of pregnancy.

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.

Studies on human phenylalanine Mono-oxygenase. I. Restricted expression.

Enzyme assays for phenylalanine mono-oxygenase have been performed on a variety of non-hepatic human cell types under varying conditions. The cell types studied were cultured fibroblasts, short-term lymphocyte cultures, long-term lymphoblastoid cultures, cultured amniotic fluid cells, hair roots and placental extracts. The cultured cells were assayed after growth under standard conditions and in the presence of a high concentration of substrate, a low concentration of end-product, added hydrocortisone or dexamethasone and under combinations of these conditions. In no instance was a significant enzyme activity obtained.

Partial monosomy 7 with interstitial deletions in two infants with differing congenital abnormalities.

Two cases of interstitial deletion of chromosome 7 are presented, one involving the short arm and the other the long arm. The cytogenetic, dermatoglyphic, and clinical findings are compared with previously reported cases of chromosome 7 deletion. The patient with a short arm deletion differs clinically from the previously reported cases but, in common with a least one previous case, has a low total finger ridge count. His interstitial deletion involving the 7p13 leads to 7p21 region also differs from 7p deletions reported in earlier cases. The patient with a long arm deletion has an interstitial loss of the region between 7q11 and 7q21, corresponding to one of three groups of 7q deletion that have been recognised. The phenotypic changes in this group are less well defined than in the other two and the patient presented here differs clinically from the previously reported cases, apart from one phenotypically normal mosaic case, in lacking morphological abnormalities. He shares with one previous case both epilepsy and a high intensity of dermal ridge patterns.