VISIBILITY OF ANTERIOR BORDER-RING OF SCHWALBE IN CONGENITAL CORNEAL ANOMALIES, TUMOURS OF THE LIMBUS AND DENTAL ANOMALIES

Toward the complete genomic map and molecular pathology of human chromosome 4

The identification of disease genes via molecular DNA cloning has revolutionized human genetics and medicine. Both the candidate gene approach and positional cloning have been used successfully. The defects causing Huntington's disease, facioscapulohumeral muscular dystrophy, piebaldism, Hurler/Scheie syndrome, one form of autosomal recessive retinitis pigmentosa, and a second locus for autosomal dominant polycystic kidney disease have recently been localized to chromosome 4. In addition to the rapid progress in the cloning of the 203-megabase chromosome, the presence of more than 60 closely spaced microsatellites on this chromosome will undoubtedly lead to the localization of additional disease genes. In order to consider cloned genes as potential candidates for disorders assigned to chromosome 4, it is important to collect and order all genes with respect to their chromosomal localization. Analysis of cytogenetically visible interstitial and terminal deletions should also be helpful in defining new disease gene loci and in mapping novel genes. These data represent the status quo of the integrated molecular map for chromosome 4.

The Rieger syndrome and a chromosome 13 deletion

The Rieger syndrome, characterized by a prominent Schwalbe line, iris strands to the cornea, iris hypoplasia, dental abnormalities, facial malformations, and umbilical defects, is inherited in an autosomal dominant pattern. We studied a boy with the ocular features of the Rieger syndrome, micrognathia, and redundancy of the periumbilical skin. Chromosome analysis revealed an interstitial deletion of the long arm of chromosome 13 involving the distal region of band q14 through band q31. As there was a previous report of the Rieger syndrome in a child with an interstitial deletion of chromosome 13 (q12,q22), we suggest that a gene for this disorder may be located in the segment q14 to q22.

Crystalline stromal dystrophy: histochemistry and ultrastructure of the cornea

A report of a woman in her fifties with Schnyder's crystalline stromal dystrophy is presented. There is no personal or family history of hypercholesterolaemia. A full thickness corneal disc was removed before grafting and examined by polarised light, histochemistry, and electron microscopy. Specific lipid histochemical methods showed deposits of cholesterol and cholesterol ester in the superficial stroma and in Bowman's membrane, but no triglyceride or free fatty acids were detected. Electron microscopy showed disruption of the superficial corneal stroma and Bowman's zone by cholesterol crystals and the presence of extracellular lamellated lipid droplets with a 4-4.5 nm periodicity. The epithelium, endothelium, and Descemet's membrane were virtually unaffected. The role of corneal grafting in crystalline stromal dystrophy is evaluated and the possible mechanisms of lipid accumulation in this disease are discussed.

The Axenfeld syndrome and the Rieger syndrome

A family is reported in which both the syndrome of Axenfeld and the eye malformations of the syndrome of Rieger occur, indicating that both may be expressions of the same gene. We also review the associated anomalies already reported, emphasise their high incidence, suggest that these are not accidental associations, and propose some possible explanations for the high incidence.

The Rieger syndrome

Fourteen patients with hypodontia and the ocular features of the Rieger syndrome were examined for the presence of systemic anomalies. A periumbilical defect that consisted of failure of the periumbilical skin to involute was seen in ten of the thirteen evaluated for the defect. Three others had scars over the umbilical area and had a history of surgery for herniation. In addition, four males in one family and one male from another family had hypospadias. None of several other anomalies reported to be components of the Rieger syndrome by other authors was detected in the fourteen patients. The mode of inheritance in the familial cases studied was compatible with autosomal dominance. The results of this study indicate that the Rieger syndrome is an autosomal dominant syndrome whose cardinal features are hypodontia, goniodysgenesis, and failure of the periumbilical skin to involute properly.

Inherited variation in Rieger's malformation

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