NORMAL GENOMIC

• Heil SG, Levtchenko E, Monnens LA, Trijbels FJ, Van Der Put NM, Blom HJ
• The molecular basis of dutch infantile nephropathic cystinosis.
• Nephron. 2001; 89: 50-5
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• Infantile nephropathic cystinosis, an inborn error of metabolism with an autosomal recessive inheritance pattern, is characterized by lysosomal storage of the amino acid cystine due to an impaired transport of cystine out of the lysosomes. Initial clinical features consist of the renal Fanconi syndrome and crystals in the cornea. Oral therapy with cysteamine lowers the intracellular cystine content. Recently, the gene coding for the integral membrane protein cystinosin, which is responsible for membrane transport of cystine (CTNS), was cloned. Mutation analysis of the CTNS gene of Caucasian patients revealed a common 57-kb deletion, and several other mutations spread throughout the entire gene. In the present study, we developed an improved screening method for the detection of the common 57-kb deletion. By use of this method we detected the 57-kb deletion in 59% of the examined Dutch alleles. The remaining alleles were screened for other mutations by genomic sequencing of the different exons, revealing three previously described mutations. Furthermore, we studied a possible genotype-phenotype relation of the homozygous deleted patients, which could not be demonstrated in our study population. Next to biochemical determination of cystine in leukocytes or fibroblasts, molecular genetic analysis enables prenatal diagnosis and facilitates identification of carriers. Copyright 2001 S. Karger AG, Basel

• Kalatzis V et al.
• Characterization of a putative founder mutation that accounts for the high incidence of cystinosis in Brittany.
• J Am Soc Nephrol. 2001; 12: 2170-4
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• Cystinosis is an autosomal recessive disorder, characterized by an accumulation of intralysosomal cystine, with an incidence of 1 in 100,000 to 200,000 live births. A higher incidence of cystinosis, 1 in 26,000 live births, has been reported in the western French province of Brittany. PCR amplification and sequencing has identified a 27-bp deletion starting 3 bp before the end of exon 8 and continuing into intron 8, 898-900+24del27, which has only been detected in families from this region. Reverse transcription-PCR amplification of RNA from an affected individual has shown that this mutation is indeed a splice-site mutation and results in the production of aberrant transcripts. These transcripts are predicted to either severely truncate cystinosin or alter its topology, thus accounting for the severe phenotype of these individuals. The mutation 898-900+24del27 has been identified in 7 of 18 alleles studied. This mutation is likely to be a founder mutation and would account for the higher incidence of cystinosis in Brittany.(1)

• Rupar CA, Matsell D, Surry S, Siu V
• A G339R mutation in the CTNS gene is a common cause of nephropathic cystinosis in the south western Ontario Amish Mennonite population.
• J Med Genet. 2001; 38: 615-6

• Kohl S et al.
• Mutations in the CNGB3 gene encoding the beta-subunit of the cone photoreceptor cGMP-gated channel are responsible for achromatopsia (ACHM3) linked to chromosome 8q21.
• Hum Mol Genet. 2000; 9: 2107-16
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• Achromatopsia is an autosomal recessive disorder featuring total colour blindness, photophobia, reduced visual acuity and nystagmus. While mutations in the CNGA3 gene on chromosome 2q11 are responsible for achromatopsia in a subset of patients, previous linkage studies have localized another achromatopsia locus, ACHM3, on chromosome 8q21. Using achromatopsia families in which CNGA3 mutations have been excluded, we refined the ACHM3 locus to a 3.7 cM region enclosed by markers D8S1838 and D8S273. Two yeast artificial chromosome (YAC) contigs covering nearly the entire ACHM3 interval were constructed. Database searches with YAC content sequences identified two overlapping high throughput genomic sequencing phase (HTGS) entries which contained sequences homologous to the murine cng6 gene encoding the putative beta-subunit of the cone photoreceptor cGMP-gated channel. Using RT-PCR and RACE, we identified and cloned the human cDNA homologue, designated CNGB3, which encodes an 809 amino acid polypeptide. Northern blot analysis revealed a major transcript of approximately 4.4 kb specifically expressed in the retina. The human CNGB3 gene consists of 18 exons distributed over approximately 200 kb of genomic sequence. Analysis of the CNGB3 gene in achromats revealed six different mutations including a missense mutation (S435F), two stop codon mutations (R203X and E336X), a 1 bp and an 8 bp deletion (1148delC and 819-826del) and a putative splice site mutation of intron 13. The 1148delC mutation was identified recurrently in several families, and in total was present on 11 of 22 disease chromosomes segregating in our families.

• Touchman JW et al.
• The genomic region encompassing the nephropathic cystinosis gene (CTNS): complete sequencing of a 200-kb segment and discovery of a novel gene within the common cystinosis-causing deletion.
• Genome Res. 2000; 10: 165-73
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• Nephropathic cystinosis is an autosomal recessive disorder caused by the defective transport of cystine out of lysosomes. Recently, the causative gene (CTNS) was identified and presumed to encode an integral membrane protein called cystinosin. Many of the disease-associated mutations in CTNS are deletions, including one >55 kb in size that represents the most common cystinosis allele encountered to date. In an effort to determine the precise genomic organization of CTNS and to gain sequence-based insight about the DNA within and flanking cystinosis-associated deletions, we mapped and sequenced the region of human chromosome 17p13 encompassing CTNS. Specifically, a bacterial artificial chromosome (BAC)-based physical map spanning CTNS was constructed by sequence-tagged site (STS)-content mapping. The resulting BAC contig provided the relative order of 43 STSs. Two overlapping BACs, which together contain all of the CTNS exons as well as extensive amounts of flanking DNA, were selected and subjected to shotgun sequencing. A total of 200,237 bp of contiguous, high-accuracy sequence was generated. Analysis of the resulting data revealed a number of interesting features about this genomic region, including the long-range organization of CTNS, insight about the breakpoints and intervening DNA associated with the common cystinosis-causing deletion, and structural information about five genes neighboring CTNS (human ortholog of rat vanilloid receptor subtype 1 gene, CARKL, TIP-1, P2X5, and HUMINAE). In particular, sequence analysis detected the presence of a novel gene (CARKL) residing within the most common cystinosis-causing deletion. This gene encodes a previously unknown protein that is predicted to function as a carbohydrate kinase. Interestingly, both CTNS and CARKL are absent in nearly half of all cystinosis patients (i.e., those homozygous for the common deletion). [The sequence data described in this paper have been submitted to the GenBank data library under accession nos. AF168787 and AF163573.]

• Cherqui S, Kalatzis V V, Forestier L, Poras I I, Antignac C
• Identification and Characterisation of the Murine Homologue of the Gene Responsible for Cystinosis, Ctns.
• BMC Genomics. 2000; 1: 2-2
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• BACKGROUND: Cystinosis is an autosomal recessive disorder characterised by an intralysosomal accumulation of cystine, and affected individuals progress to end-stage renal failure before the age of ten. The causative gene, CTNS, was cloned in 1998 and the encoded protein, cystinosin, was predicted to be a lysosomal membrane protein. RESULTS: We have cloned the murine homologue of CTNS, Ctns, and the encoded amino acid sequence is 92.6% similar to cystinosin. We localised Ctns to mouse chromosome 11 in a region syntenic to human chromosome 17 containing CTNS. Ctns is widely expressed in all tissues tested with the exception of skeletal muscle, in contrast to CTNS. CONCLUSIONS: We have isolated, characterised and localised Ctns, the murine homologue of CTNS underlying cystinosis. Furthermore, our work has brought to light the existence of a differential pattern of expression between the human and murine homologues, providing critical information for the generation of a mouse model for cystinosis.

• Moller LB, Petersen C, Lund C, Horn N
• Characterization of the hCTR1 gene: genomic organization, functional expression, and identification of a highly homologous processed gene.
• Gene. 2000; 257: 13-22
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• The human hCTR1 gene was originally identified by its ability to complement a yeast mutant deficient in high-affinity copper uptake (Zhou, B., Gitschier, J., 1997. A human gene for copper uptake identified by complementation in yeast. Proc. Natl. Acad. Sci. USA 94, 7481-7486). Here, we have determined the DNA sequence of the exon-intron borders of the hCTR1 structural gene and report that the coding sequence is disrupted by three introns, all of which comply with the GT/AG rule. Furthermore, human fibroblasts, transfected with hCTR1 cDNA, were shown to have a dramatically increased capacity for (64)Cu uptake, indicating that the hCtr1 protein is functional in copper uptake in human cells. In contrast, no evidence was found for involvement of the hCTR2 gene product in copper uptake. Finally, we have identified a highly homologous processed pseudogene, hCTR1psi, which was localized to chromosome 3q25/26. The processed gene was found to be transcribed, but due to a frame shift mutation, it only had the potential to encode a truncated protein of 95 amino acid residues, and cells transfected with hCTR1psi DNA showed no increase of (64)Cu uptake.

• Anikster Y et al.
• Ocular nonnephropathic cystinosis: clinical, biochemical, and molecular correlations.
• Pediatr Res. 2000; 47: 17-23
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• Ocular nonnephropathic cystinosis, a variant of the classic nephropathic type of cystinosis, is an autosomal recessive lysosomal storage disorder characterized by photophobia due to corneal cystine crystals but absence of renal disease. We determined the molecular basis for ocular cystinosis in four individuals. All had mutations in the cystinosis gene CTNS, indicating that ocular cystinosis is allelic with classic nephropathic cystinosis. The ocular cystinosis patients each had one severe mutation and one mild mutation, the latter consisting of either a 928 G-->A (G197R) mutation or an IVS10-3 C-->G splicing mutation resulting in the insertion of 182 bp of IVS10 into the CTNS mRNA. The mild mutations appear to allow for residual CTNS mRNA production, significant amounts of lysosomal cystine transport, and lower levels of cellular cystine compared with those in nephropathic cystinosis. The lack of kidney involvement in ocular cystinosis may be explained by two different mechanisms. On the one hand (e.g. the G197R mutation), significant residual cystinosin activity may be present in every tissue. On the other hand (e.g. the IVS 10-3 C-->G mutation), substantial cystinosin activity may exist in the kidney because of that tissue's specific expression of factors that promote splicing of a normal CTNS transcript. Each of these mechanisms could result in minimally reduced lysosomal cystine transport in the kidneys.

• Bassi MT, Manzoni M, Monti E, Pizzo MT, Ballabio A, Borsani G
• Cloning of the gene encoding a novel integral membrane protein, mucolipidin-and identification of the two major founder mutations causing mucolipidosis type IV.
• Am J Hum Genet. 2000; 67: 1110-20
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• Mucolipidosis type IV (MLIV) is an autosomal recessive lysosomal storage disorder characterized by severe psychomotor retardation and ophthalmologic abnormalities, including corneal opacity, retinal degeneration, and strabismus. Unlike the situation in other lysosomal disorders, the accumulation of heterogeneous storage material observed in MLIV does not result from a block in the catabolic pathways but is due to an ill-defined transport defect in the late steps of endocytosis. With the aim of cloning the MLIV gene, we searched in the 19p13.2-13.3 region, where the locus previously had been assigned by linkage mapping. In this region, we have identified a novel gene that is mutated in all patients with MLIV who were enrolled in our study. One patient was homozygous for the splice-acceptor mutation, and another was homozygous for a deletion removing the first six exons of the gene. In addition, four compound heterozygotes for these two mutations were identified. Haplotype analysis indicates that we have identified the two major founder mutations, which account for >95% of MLIV chromosomes in Ashkenazi Jewish patients. The gene, ML4, encodes a protein named "mucolipidin, " which localizes on the plasma membrane and, in the carboxy-terminal region, shows homologies to polycystin-2, the product of the polycystic kidney disease 2 gene (PKD2) and to the family of transient receptor potential Ca(2+) channels. Mucolipidin is likely to play an important role in endocytosis.

• Thoene J et al.
• Mutations of CTNS causing intermediate cystinosis.
• Mol Genet Metab. 1999; 67: 283-93
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• Six patients with the intermediate form of cystinosis are described. Two have new mutations not previously described. The disease occurs due either to the combination of one mild mutation and one which is known to cause nephropathic cystinosis or to homozygosity for a predicted mild mutation. Partial phenotypic correction of cystinotic fibroblasts by transfection with normal cDNA or a cDNA derived from a mutation causing intermediate cystinosis is demonstrated.

• McGowan-Jordan J et al.
• Molecular analysis of cystinosis: probable Irish origin of the most common French Canadian mutation.
• Eur J Hum Genet. 1999; 7: 671-8
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• Infantile nephropathic cystinosis, an autosomal recessive disease characterized by a lysosomal accumulation of cystine, presents as failure to thrive, rickets and proximal renal tubular acidosis. The cystinosis gene, CTNS, which maps to chromosome 17p13, encodes a predicted 55 kDa protein with characteristics of a lysosomal membrane protein. We have conducted extensive linkage analysis in a French Canadian cystinosis cohort identifying a founding haplotype present in approximately half (21/40) of the chromosomes studied. Subsequent mutational analysis, in addition to identifying two novel mutations, has unexpectedly revealed a mutation which has been previously found in Irish (but not French) cystinotic families on these 21 French Canadian chromosomes. Haplotype analysis of two Irish families with this mutation supports the hypothesis that Celtic chromosomes represent an extensive portion of cystinosis chromosomes in French Canada. Our analysis underlines the genetic heterogeneity of the French Canadian population, reflecting a frequently unrecognized contribution from non-Gallic sources including the Irish.

• Anikster Y, Shotelersuk V, Gahl WA
• CTNS mutations in patients with cystinosis.
• Hum Mutat. 1999; 14: 454-8
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• Cystinosis is an autosomal recessive lysosomal storage disease caused by mutations in the gene CTNS. The CTNS gene product, cystinosin, has 367 amino acids and seven transmembrane domains and is thought to transport cystine out of lysosomes. The most common form of cystinosis, the nephropathic or infantile type, is characterized by renal failure at 10 years of age and other systemic complications. To date, 32 different CTNS mutations have been described in nephropathic cystinosis patients. Intermediate cystinosis, with later onset of renal disease, has been associated with three different CTNS mutations. Benign or nonnephropathic cystinosis, with symptoms related only to corneal crystals and photophobia, has been associated with two other CTNS mutations. In general, only certain splicing or missense mutations are associated with milder cystinosis phenotypes. Hum Mutat 14:454-458, 1999. Published 1999 Wiley-Liss, Inc.

• Forestier L et al.
• Molecular characterization of CTNS deletions in nephropathic cystinosis: development of a PCR-based detection assay.
• Am J Hum Genet. 1999; 65: 353-9
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• Nephropathic cystinosis is an autosomal recessive disorder that is characterized by accumulation of intralysosomal cystine and is caused by a defect in the transport of cystine across the lysosomal membrane. Using a positional cloning strategy, we recently cloned the causative gene, CTNS, and identified pathogenic mutations, including deletions, that span the cystinosis locus. Two types of deletions were detected-one of 9.5-16 kb, which was seen in a single family, and one of approximately 65 kb, which is the most frequent mutation found in the homozygous state in nearly one-third of cystinotic individuals. We present here characterization of the deletion breakpoints and demonstrate that, although both deletions occur in regions of repetitive sequences, they are the result of nonhomologous recombination. This type of mechanism suggests that the approximately 65-kb deletion is not a recurrent mutation, and our results confirm that it is identical in all patients. Haplotype analysis shows that this large deletion is due to a founder effect that occurred in a white individual and that probably arose in the middle of the first millenium. We also describe a rapid PCR-based assay that will accurately detect both homozygous and heterozygous deletions, and we use it to show that the approximately 65-kb deletion is present in either the homozygous or the heterozygous state in 76% of cystinotic patients of European origin.

• Anikster Y et al.
• Identification and detection of the common 65-kb deletion breakpoint in the nephropathic cystinosis gene (CTNS).
• Mol Genet Metab. 1999; 66: 111-6
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• The most common mutation in the cystinosis gene, CTNS, is a 65-kb deletion thought to have originated in Germany. Although homozygotes for this deletion are detectable by the absence of the D17S829 polymorphic marker, no method exists to identify heterozygotes. We identified the 65-kb deletion breakpoints and used flanking PCR primers to amplify a 423-bp fragment present only in the deletion alleles. Using this method, we determined that 121 of 216 (56%) cystinosis alleles examined bore the 65-kb deletion. We found no non-Europeans with the deletion, and the deletion size and breakpoints appeared identical in all patients studied, supporting the concept of a founder effect. The addition of D17S829 primers (266 bp apart) to the PCR created a multiplex PCR system useful for diagnosing cystinosis patients homozygous and heterozygous for the 65-kb deletion.

• Shotelersuk V et al.
• CTNS mutations in an American-based population of cystinosis patients.
• Am J Hum Genet. 1998; 63: 1352-62
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• Nephropathic cystinosis is an autosomal recessive lysosomal storage disease characterized by renal failure at 10 years of age and other systemic complications. The gene for cystinosis, CTNS, has 12 exons. Its 2.6-kb mRNA codes for a 367-amino-acid putative cystine transporter with seven transmembrane domains. Previously reported mutations include a 65-kb "European" deletion involving marker D17S829 and 11 small mutations. Mutation analysis of 108 American-based nephropathic cystinosis patients revealed that 48 patients (44%) were homozygous for the 65-kb deletion, 2 had a smaller major deletion, 11 were homozygous and 3 were heterozygous for 753G-->A (W138X), and 24 had 21 other mutations. In 20 patients (19%), no mutations were found. Of 82 alleles bearing the 65-kb deletion, 38 derived from Germany, 28 from the British Isles, and 4 from Iceland. Eighteen new mutations were identified, including the first reported missense mutations, two in-frame deletions, and mutations in patients of African American, Mexican, and Indian ancestry. CTNS mutations are spread throughout the leader sequence, transmembrane, and nontransmembrane regions. According to a cystinosis clinical severity score, homozygotes for the 65-kb deletion and for W138X have average disease, whereas mutations involving the first amino acids prior to transmembrane domains are associated with mild disease. By northern blot analysis, CTNS was not expressed in patients homozygous for the 65-kb deletion but was expressed in all 15 other patients tested. These data demonstrate the origins of CTNS mutations in America and provide a basis for possible molecular diagnosis in this population.

• McDowell GA, Town MM, van't Hoff W, Gahl WA
• Clinical and molecular aspects of nephropathic cystinosis.
• J Mol Med. 1998; 76: 295-302
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• Nephropathic cystinosis, an autosomal recessively inherited lysosomal storage disease, results from impaired transport of the disulfide amino acid cystine out of cellular lysosomes. The consequent accumulation and crystallization of cystine destroys tissues, causing growth retardation in infancy, renal failure at 10 years of age, and a variety of other complications. Early oral therapy with the cystine-depleting agent cysteamine prevents renal deterioration and enhances growth. Although the lysosomal cystine carrier has been extensively studied, its molecular structure remains unknown. The lysosomal cystine transporter gene has been mapped by linkage analysis to human chromosome 17p between polymorphic microsatellite markers D17S1583 and D17S1584. Pertinent recombination events and homozygosity by descent has verified that the cystinosis gene lies in the 3.6 cM genetic interval between these two markers. The cystinosis region has been substantially reduced in size by the observation of recombination events in cystinosis patients between markers D17S1828 and D17S2167. According to radiation hybrid analysis, these two markers are separated by 10.2 cR8000 (centirad using 8000 rad radiation hybrids). Estimates of the physical size of this interval range from 187 to 510 kb. Four yeast artificial chromosomes have been identified which form a contig covering the original cystinosis region. Two P1 clones together may span the new, smaller interval, meaning that the cystinosis gene would lie on one of them. Current efforts are being directed toward using these P1 clones to isolate candidate cDNAs by a variety of methods. The ultimate cloning of the cystinosis gene will reveal how functional lysosomal porters are synthesized, targeted, processed, and integrated into the lysosomal membrane.

• Broyer M
• [Infantile cystinosis]
• Rev Prat. 1997; 47: 1550-3
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• Infantile cystinosis is a metabolic lysosomal storage disease of cystine affecting most of the body cells. The first symptoms appear after 5-6 months of life: anorexia, vomiting, polyuria, polydipsia and failure to thrive, associated with the signs of tubular Fanconi syndrome including glycosuria, proteinuria, loss of bicarbonate, phosphate, potassium, sodium, etc. Treatment with cysteamine is effective if started as early as possible. This treatment delays or prevents the spontaneous evolution toward end-stage renal failure, usually between 6 and 12 years of age, and also prevents growth stunting. In the long term, other organs may be involved like eye, thyroid, endocrine pancreas, muscle and central nervous system. The diagnosis is ascertained by leucocytes cystine assay, also useful for the follow up and the adjustment of the treatment. Prenatal diagnosis is available on chorionic sample. The gene of the disease is not yet identified but is known to map to chromosome 17.

• Ballantyne AO, Scarvie KM, Trauner DA
• Academic achievement in individuals with infantile nephropathic cystinosis.
• Am J Med Genet. 1997; 74: 157-61
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• The present study examined academic skills in children and young adults with infantile nephropathic cystinosis. Cystinosis is a genetic metabolic disorder in which the amino acid cystine accumulates in various tissues and organs, including the kidney, cornea, thyroid, and brain. Individuals with cystinosis have normal intelligence but subtle visual processing impairments. Subjects were 19 children and young adults with cystinosis and 19 age-, sex-, and IQ-matched controls. All subjects had IQs within the normal range. On a test of academic achievement, mean standard scores for cystinosis and control subjects, respectively, were as follows: arithmetic 89.95 +/- 13.77 vs. 102.16 +/- 9.62; spelling 90.68 +/- 18.81 vs. 98.00 +/- 10.96; reading 97.47 +/- 15.59 vs. 98.58 +/- 12.41. Multivariate analysis of variance revealed a significant main effect for Group (P = .009); there was no main effect for Sex, nor was there a Group x Sex interaction. Univariate follow-up tests indicated that the cystinosis group performed significantly more poorly than did controls on the arithmetic subtest (P = .001) and that there was a trend (P = .085) toward poorer performance by the cystinosis group on the spelling subtest. Regression analyses revealed no evidence of a developmental lag or deterioration of function with age. The visual processing deficits previously identified in these individuals may underlie the academic difficulties observed here. It is possible that both visual processing and academic difficulties may reflect a common mechanism of selective cortical damage by this genetic defect.

• Jean G et al.
• High-resolution mapping of the gene for cystinosis, using combined biochemical and linkage analysis.
• Am J Hum Genet. 1996; 58: 535-43
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• Infantile nephropathic cystinosis is an autosomal recessive disorder characterized biochemically by an abnormally high intracellular content of free cystine in different organs and tissues due to a transport defect of cystine through the lysosomal membrane. Affected children present with the Fanconi syndrome and usually develop progressive renal failure within the 1st decade of life. Measurement of free cystine in purified polymorphonuclear leukocytes provides an accurate method for diagnosis and detection of heterozygous carriers. In order to localize the gene locus for cystinosis we performed linkage analysis in 18 cystinosis families. However, since 17 of these were simplex families, we decided to include the phenotypes of the heterozygous carriers previously determined by their leukocyte cystine content in the linkage analysis. This approach allowed us to obtain highly significant results, confirming the localization of the cystinosis gene locus recently mapped to the short arm of chromosome 17 by the Cystinosis Collaborative Research Group. Crucial recombination events allowed us to refine the interval of the cystinosis gene to a genetic distance of 1 cM. No evidence of genetic heterogeneity was found. Our results demonstrate that the use of the previously determined phenotypes of heterozygous carriers in linkage analysis provides a reliable method for the investigation of simplex families in autosomal recessive traits.

• Thoene JG
• Cystinosis.
• J Inherit Metab Dis. 1995; 18: 380-6
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• Nephropathic cystinosis is an autosomal recessive inborn error of metabolism characterized by the lysosomal storage of the disulphide amino acid cystine. It produces a variety of clinical manifestations including failure to thrive, the renal Fanconi syndrome, eye findings, and end-stage renal disease. A variety of phenotypes are known; however, the molecular defect underlying any of the forms has not yet been identified. Therapy of cystinosis with cysteamine averts the otherwise inevitable renal failure, but systemic therapy does not improve the corneal keratopathy. A number of presentations in this review detail approaches to gene identification, systemic therapy with cysteamine, measurement of cystine, and pathophysiological effects at the cellular and clinical level.

• Gahl WA, Bashan N, Tietze F, Schulman JD
• Lysosomal cystine counter-transport in heterozygotes for cystinosis.
• Am J Hum Genet. 1984; 36: 277-82
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• 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.

• Yudkoff M, Foreman JW, Segal S
• Effects of cysteamine therapy in nephropathic cystinosis.
• N Engl J Med. 1981; 304: 141-5
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• We studied the effects of cysteamine in five children with nephropathic cystinosis who were treated for up to 30 months. Cysteamine caused a decline in leukocyte cystine levels to the range seen in clinically unaffected heterozygotes; both plasma and urinary cystine diminished by more than half. Therapy had no effect on progressively declining creatinine clearance in three patients, but improvement occurred in the other two. Phosphaturia, glycosuria, aminociduria, and organic aciduria did not improve in any of the patients. Both blood lactate and the lactate pyruvate ratio were diminished. Growth velocity, which was abnormal in four of the five children, did not improve. No major side effects were noted. Therapy with cysteamine caused a consistent, dose-related decline in levels of cystine in leukocytes and in extracellular fluid, caused no improvement so far in renal tubular function or growth velocity, and improved creatinine clearance in some patients.

• Thiel HJ, Voigt GJ, Dorner K, Hake H, von Denffer H
• [Nephropathic and benign cystinosis (author's transl)]
• Klin Monatsbl Augenheilkd. 1980; 177: 324-35
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• 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.