title: Coexistence of macular corneal dystrophy types I and II in a single sibship.
abstract: BACKGROUND
  Macular corneal dystrophy (MCD) is an inherited autosomal recessive disorder that has been subdivided into two primary immunophenotypes, MCD types I and II. The MCD type I gene has been localised previously to chromosome 16q22 and suggestive evidence provided that MCD type II gene is also linked to this region. Here an unusual family is reported where both MCD types I and II are found in a single sibship.
  
  
  METHODS
  Immunoreactivity to an anti-keratan sulphate monoclonal antibody (5-D-4) was evaluated in patients' serum and in corneal tissue obtained at keratoplasty. Chromosomal haplotypes were constructed using microsatellite repeat markers spanning the region of the MCD type I locus.
  
  
  RESULTS
  Immunological studies demonstrated that two of the affected siblings have MCD type II while one has MCD type I. Haplotype analysis suggests that all three affected sibs inherited one identical parental haplotype. However, the two MCD types differ in their alternative chromosome with both MCD type II children sharing an identical haplotype, different from their MCD type I sibling.
  
  
  CONCLUSIONS
  The findings in this study support the hypothesis that the genes for MCD types I and II co-localise to the same region of chromosome 16 and are likely to be due to allelic manifestations of the same abnormal gene.
authors.affiliation: Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: N P
authors.initials: NP
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Baldwin
authors.forename: F
authors.initials: F
authors.lastname: Lennon
authors.forename: J M
authors.initials: JM
authors.lastname: Stajich
authors.forename: E J
authors.initials: EJ
authors.lastname: Thonar
authors.forename: M A
authors.initials: MA
authors.lastname: Pericak-Vance
authors.forename: G K
authors.initials: GK
authors.lastname: Klintworth
authors.forename: J M
authors.initials: JM
authors.lastname: Vance
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003317:Corneal Dystrophies, Hereditary / Q000145:classification / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005819:Genetic Markers; D006239:Haplotypes; D006801:Humans; D016130:Immunophenotyping; D007632:Keratan Sulfate / Q000097:blood; D008297:Male; D018895:Microsatellite Repeats; D010375:Pedigree; D016133:Polymerase Chain Reaction
chemical_list: D005819:Genetic Markers; D007632:Keratan Sulfate