Trichothiodystrophy: Current Concepts
Vera H. Price
Background: Trichodystrophy
(TTD) is a rare, autosomal recessive disorder in which the hair
identifies a group of genetic disorders with deficient
high-sulfur matrix proteins, and a defect in excision repair of
ultraviolet damage in fibroblasts of most patients. TTD patients
may be grouped as follows: (1) the major group with defects in
the excision repair cross-complementing gene ERCC2, the gene for
xerderma pigmentosum group D (XP-D); (2) those with a repair
defects distinct from those in XP patients, TTD patients have no
increased frequency of skin cancers.
Objective: The article explains
the relationship of TTD and XP and helps clarify why TTD patients
with defects in the same gene(s) as those with XP do not have
increased skin cancers.
Methods: Methods includes
biochemical studies, mutational analysis, and genomic sequence
analysis of cell lines from skin biopsies of TTD and XP patients.
Results: The ERCC2 gene is a
component of the TFIIH complex which controls two distinct
DNA-meabolizing processes, transcription initiation and
nucleotide excision repair.
Conclusion: In TTD, the major
defect is in transcription initiation, whereas in XP-D, DNA
repair is primarily altered.
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