Cataract in a fetus at risk for oculo-cerebro-renal syndrome (Lowe)

Inherited metabolic diseases affecting the carrier

The objective of this review is to draw attention to those inherited metabolic traits which are potentially harmful also for the carrier, and to outline preventive measures, at least for obligate heterozygotes, i.e. parents of homozygous children. Concerning carriers of food-dependent abnormalities, early vascular disease in homocystinuria, hyperammonaemic episodes in ornithine transcarbamylase deficiency, presenile cataracts in galactosaemia as well as galactokinase deficiency, spastic paraparesis in X-linked adrenoleukodystrophy, and HELLP syndrome in mothers of babies with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency have to be mentioned. In the group of food-independent disorders, clinical features in carriers may be paraesthesias and corneal dystrophy in Fabry disease, lens clouding in Lowe syndrome, lung and/or liver diseases in alpha 1-antitrypsin deficiency, and renal stones in cystinuria type II and III. Finally, two monogenic carrier states are known which in pregnant individuals could possibly afflict the developing fetus, i.e. heterozygosity for galactosaemia and for phenylketonuria. Elevated levels of galactose-1-phosphate have been found in red blood cells of infants heterozygous for galactosaemia born to heterozygous mothers. Aspartame in very high doses is reported to increase blood phenylalanine levels in heterozygotes for phenylketonuria, thus being a risk for the fetus of a heterozygous mother. For some of these carrier states preventive measures can be recommended, e.g. restriction of lactose in parents and heterozygous grandparents of children with galactosaemia and galactokinase deficiency as well as transiently in infants heterozygous for galactosaemia, dietary supplementation with monounsaturated fatty acids in symptomatic carriers for X-linked adrenoleukodystrophy, avoidance of smoking and alcohol in heterozygotes for alpha 1-antitrypsin deficiency, avoidance of episodes of dehydration in heterozygotes for cystinuria, and restriction of aspartame in pregnant women.

Clinicopathologic and molecular-pathologic approaches to Lowe's syndrome

The oculocerebrorenal syndrome of Lowe (OCRL), an X-linked disorder involving several organ systems, including the eyes, nervous system, and kidneys, is often difficult to diagnose because few pathologic data of diagnostic features about OCRL are available, and its rarity has hampered comprehensive investigations into its clinical spectrum. Recently, the genetic and biochemical abnormalities responsible for this syndrome have been reported. We have synthesized a cDNA probe of the OCRL locus using a polymerase chain reaction, in which there is no homology of cDNA sequence with human inositol polyphosphate-5-phosphatase (HUMINP5P); we have taken a genetic approach to diagnose this disorder in a 10-year-old male by using Northern blotting and have demonstrated the expression of mRNA in human tissues of a 17-week fetus by in situ hybridization. This paper presents a new method that should be an easy and helpful tool for diagnosing OCRL and that contributes a new aspect of this syndrome through in situ hybridization histochemical staining of normal fetal tissues.

Cataract and metabolic disease

In addition to the already recognized metabolic diseases which have been associated with cataract formation, e.g. galactosaemia, galactokinase deficiency, Lowe's syndrome and diabetes, several other disorders can also lead to the development of cataracts. They are sorbitol dehydrogenase deficiency, uridine diphosphate galactose-4-epimerase deficiency, marginal maternal transferase and galactokinase deficiency, galactitol and sorbitol accumulation of unknown origin, heterozygosity for galactosaemia and galactokinase deficiency as well as the carrier state for Lowe's syndrome. In this review these metabolic disorders have been divided into five groups according to the age at the first appearance of lens clouding and the possible means of treatment have been discussed.

Pathogenesis of cataracts in patients with Lowe's syndrome

Based on our morphologic and ultrastructural studies, we suggest that the characteristic lens opacities in Lowe's syndrome result from a genetic defect in the lens cells. This defect manifests early in embryogenesis, and the progression of the lens opacities is related to both the inherent genetic abnormality and the prevailing extralenticular environment. The defective formation and subsequent degeneration of the primary posterior lens fibers account for their loss and for the flattened, discoid, or ring-shaped cataract. The other findings, such as anterior polar cataract, subcapsular fibrous plaque, capsular excrescences, bladder cells, and posterior lenticonus are not necessarily specific for Lowe's syndrome. We believe that the pathogenesis of Lowe's cataract can be explained by Lyon's hypothesis, which implies that, very early in embryogenesis (at the stage of the primitive streak), one of the two X chromosomes in females is deactivated. We consider the high incidence of lens opacities in female carriers to be due to this random deactivation. In male probands, however, all lens cells are affected, since there is no normal X chromosome to nullify the effect of the Lowe gene.

Pathological features of the eye in the oculocerebrorenal (Lowe) syndrome

We studied the eyes of a 13-year-old boy with Lowe syndrome and updated the microscopic ocular findings. These are interpreted as a mesoectodermal dysgenesis involving the anterior and posterior segment. The eye exhibits a greater variety of morphologic change than any other organ in Lowe syndrome. The microscopic findings, particularly in the lens, are highly suggestive of this disorder. The pathogenesis of the ocular and extraocular lesions in Lowe syndrome in unknown. Most of the ocular abnormalities are probably determined in the first two months of gestation and there is no apparent embryologic relation to extraocular abnormalities. Some manifestations of Lowe syndrome may be secondary to accumulation of polyamines, a class of compounds that includes cytotoxic byproducts of faulty dibasic amino acid metabolism.