Cystinosis in the Federal Republic of Germany. Coordination and analysis of the data

In our survey, 101 infants and children with cystinosis were registered in the Federal Republic of Germany. Ninety-five patients showed the infantile type of cystinosis, five the adolescent type and one possibly the adult type. The minimum incidence rate of infantile and adolescent cystinosis in the FRG was 1 patient per 179 000 live-births. In contrast to other countries, cystinotic patients were evenly distributed in the FRG. Patients with cystinosis originated more frequently from rural communities than from large cities. Before 1968 most patients died before reaching terminal renal failure, usually due to uncontrolled disturbances of water and electrolyte metabolism. Since 1976 the causes of death other than uraemia have been rare and most patients with terminal renal failure have entered a renal replacement program.

Biochemical phenotyping of a single sibship with both cystinosis and Fabry disease

Two lysosomal storage diseases, cystinosis and Fabry disease, were diagnosed clinically in different members of a single sibship. The possibility that the affected sister and brother might have related disorders with disparate manifestations was pursued. The four principal family members were tested for heterozygote status with respect to serum and leukocyte alpha-galactosidase A activity, urinary trihexosylceramide excretion, and the capacity to engage in cystine counter-transport across leukocyte lysosome membranes. Results were consistent with classical autosomal recessive inheritance in the case of cystinosis and X-linked inheritance for Fabry disease, confirming that this family represents an example of two rare disorders occurring in the same sibship.

Lysosomal cystine counter-transport in heterozygotes for cystinosis

Heterozygotes for cystinosis exhibited approximately half the normal rate of cystine counter-transport into isolated leukocyte lysosomes. This gene-dosage effect strongly supports previous findings demonstrating that the basic defect in cystinosis is impaired cystine transport across the lysosomal membrane. The method was used to determine the cystinosis carrier status for siblings of affected children in two families with cystinosis.

Cystine accumulation and loss in normal, heterozygous, and cystinotic fibroblasts

Cystinotic fibroblasts contain approximately 100 times more cystine than do normal control fibroblasts. When cystinotic fibroblasts were placed in the presence of 30 mM cysteine-glutathione mixed disulfide (CSSG) for 24 hr, their cystine content increased about 3-fold. Similar treatment of normal fibroblasts and fibroblasts from patients heterozygous for cystinosis resulted in a 6- to 7-fold increase in cystine content. In all three cell types, the intracellular free cystine is located within lysosomes. When placed in cystine-free medium after 24 hr in CSSG-containing medium, the normal and heterozygous fibroblasts rapidly lost their lysosomal cystine (t 1/2 = 20 min), but the cystine content of the cystinotic cells remained stable for over 90 min. In contrast to the findings in intact fibroblasts, cystine loss could not be demonstrated from isolated, cystine-loaded lysosomes from any of the three cell types.

Adolescent cystinosis: a clinical and specular microscopic study of an unusual sibship

Six members of a sibship originally consisting of 8 offspring lived to teenage. Five of these developed the adolescent form of cystinosis. Since adolescent cystinosis is autosomal recessive, such a high incidence of affected members is of uncommon occurrence. Depending on whether the sibship size (n) is known as 6 to 8, it should occur only in approximately 1.5% or 5.8% of sibships of corresponding size. Specular microscopy was used to study the corneal stroma of all 3 of the living, affected members of this sibship and the conjunctiva of one of the siblings. Vivid, needle-shaped crystals were observed in the corneal stroma. Smaller, variably shaped crystals were observed in the conjunctiva. The crystals seen with specular microscopy fit the description of those studied with light and electron microscopy.

[Phaenotypic aspects of hereditary aminoacidopathies (author's transl)]

Despite considerable diagnostic progress from mass screening tests in all newborns or from sophisticated analytical efforts some patients with inborn errors of amino acid metabolism are detected only after some more or less specific clinical signs have appeared. Those may include a peculiar odor of the sweat or urine, disturbances or normal growth, and skeletal, eye, hair and skin alterations. While some of these features appear early in the course of disease and may be of diagnostic and therapeutic significance (e.g. defects in the oxidation of the branched-chain amino acids) others are noticed only in a later stage with further progress of the disease (e.g. cystathionine synthetase deficient homocystinuria tryosinemia type II, or ornithine aminotransferase deficient hyperornithinemia), when the disease may have more advanced. Therefore the physician who is engaged in the care of the newborn or takes part in any investigation program for the developing child should be aware of these signs in order to initiate further diagnostic, therapeutic, or preventive measure for the patient and his family.

Prenatal diagnosis of nephropathic cystinosis. Pregnancy at risk ascertained through heterozygote diagnosis of parents

The biochemical diagnosis of cystinosis in a deceased girl was made indirectly through the demonstration of heterozygote values of free-cystine contents in leukocytes from both parents. Amniocentesis was performed on the mother in the 16th week of two subsequent pregnancies. Amniotic fluid cell lysate from the first fetus had 6-8 times normal levels of radioactivity in the cystine band determined by a 35S-cystine pulse labeling method followed by high voltage electrophoresis on paper. Values for the cystine contents in various organs of the affected fetus are given. The second fetus was found to be not affected, and this was subsequently confirmed by the birth of a healthy child. The results of the laboratory analyses in these two cases were available to the parents 21 and 23 days following amniocentesis, respectively. The interruption of the first pregnancy was performed in the 19th week. This was 4 and 6 weeks earlier, respectively, than in the two previously reported induced abortions of affected fetuses, and should increase the acceptability of the present method for prenatal diagnosis of nephrophatic cystinosis.

[Nephropathic and benign cystinosis (author's transl)]

Cystinosis is a rare, autosomally and recessively inherited disorder of amino-acid metabolism with ocular involvement. Four patients with this disease are reported on. The clinical signs of the first patient, who had nephropathic cystinosis, are compared with the signs and symptoms of the benign phenotype (benign cystinosis). In both nephropathic and benign cystinosis, multiple crystals were found in the cornea and conjunctiva. In the second case a large number of crystals were demonstrated in bone-marrow smears and conjunctival sections; a chromatogram of the conjunctiva indicated the presence of cystine. Although the results of an analysis of cultured fibroblasts from this case were contradictory, an elevated cystine level appeared likely. Crystals were also found in conjunctival sections from the third case. In the fourth case it proved impossible to demonstrate crystals clearly in either the bone marrow or in conjunctival sections. There was no evidence of any other cause of the corneal or conjunctival crystals.

Glomerular lesions in patients with late-onset cystinosis with massive proteinuria

3 siblings--2 brothers aged 18 and 13 years, and 1 sister, aged 11 years--with adolescent or late-onset cystinosis presented with massive proteinuria. At the time their glomerular filtration rate was normal or only modestly diminished. Though glomerular injury was evident, renal tubular functional abnormalities were also present. Renal biopsy revealed histopathologic features typical of the nephropathic form of cystinosis with the Fanconi syndrome: polykaryocytosis, varying degrees of glomerular sclerosis, thickening and reduplication of basement membrane, fused foot processes, dilated tubules with altered epithelial cell features, and interstitial fibrosis. Fine granular deposits of C3 and IgM are irregularly distributed in the glomeruli, findings which have not been described in cystinosis. These deposits are possibly immune complexes being deposited in the glomeruli unrelated to the cystine-storage disease or they may represent a localized activation of the complement system induced by the glomerular injury of cystinosis.

[Adolescent cystinosis. Review of the literature and case report (author's transl)]

A case of adolescent cystinosis in a 17 1/2 year-old boy is reported. The metabolic disorder was diagnosed at the age of 13 years. Cystine was demonstrated in cornea and bone marrow and was increased in fibroblasts (3.64 nMol 1/2-cystine/mg protein). The renal lesions were characteristic of mesangioproliferative glomerulonephritis. The rate of detoriation in renal function increased from 1.5 to 6.6 mg/100 ml serum creatinine during the time of follow up. As well as the parents one brother (0.51 nMol 1/2-cystine/mg protein) appears to be a heterozygote carrier of the cystinosis gene. The striking features in adolescent cystinosis were shown by a review of the literature and the present case report.

[Late diagnosis of cystinosis in 2 brothers: histological and ultrastructural renal study]

Cystinosis was discovered by chance in two adolescent boys who had proteinuria with minor tubular abnormalities. Renal biopsies were examined by light microscopy, electron microscopy and immunofluorescence. There were few histological changes but crystals were present in the epithelial cells of the glomerulus and occasionally in the tubules. A further unusual feature was the detection of IgA deposits in the mesangium.

Inbreeding in recessive diseases

The consanguinity of parents (born in France) of individuals who have a recessive disease has been studied. The frequency of first cousin marriages is less than 0.2% in the general French population. Among the parents of affected individuals the following frequencies of first cousin matings were observed: cystic fibrosis: 1.4% cystinosis: 7.1% nephronophtisis: 5.6% spinal muscular atrophy: 4.5% albinism: 5.0% achromatopsia: 12.5% (Albinism and spinal muscular atrophy are heterogeneous conditions). The increase in the frequency of first cousin marriage relative to that of the general population is much greater, as expected, in cystinosis, which is a rare disease, than in cystic fibrosis, which is the most frequent recessive disorder in France. Inbreeding in cystinosis and cystic fibrosis was also studied by computing the distance between parental birth places. This distance is smaller in cystinosis than in cystic fibrosis.

Infantile cystinosis in France: genetics, incidence, geographic distribution

A national distribution of 66 French patients, from 49 sibships, has been studied. Segregation analysis, using the maximum likelihood method, was found to agree with the theoretical values expected in recessive autosomal inheritance. The birthplaces of these patients show an unequal geographic distribution of cystinosis, the incidence being higher in Western France. Compared with the total number of live births during the period 1959 to 1972, the minimum incidence of the condition in the province of Brittany is 1 per 25 909, and the gene frequency 0.0062. In the rest of France, the minimum incidence is 1 per 326,440 and the gene frequency 0.0018. Application of Dahlberg's formula gives a similar result. The mean inbreeding coefficient is 530 X 10(-5), a figure 23 times higher than the mean coefficient of France. An indirect test of inbreeding, the distance between parental birthplaces, was studied, first using the French administrative boundaries, second by using kilometers. This distance was constantly smaller for the parents of patients than for the parents of controls. Analysis of two erythrocyte polymorphisms (ABO and Rh) showed a large excess of group A patients when compared with overall French data. These findings are difficult to interpret on genetic grounds. The genetic reasons for the unequal geographic distribution of cystinosis in France are discussed.

[Retinopathy and maculopathy in cystinosis (author's transl)]

Retinopathy and maculopathy combined with pseudoneuritis were observed in cystinosis. The disease was classified as a nephropathic process.