Trichothiodystrophy
Below is a MRR and PLR article in category Health Fitness -> subcategory Other.
Trichothiodystrophy (TTD)
Understanding Trichothiodystrophy
Trichothiodystrophy (TTD) is a diverse group of rare, autosomal recessive disorders primarily known for causing sulfur-deficient, brittle hair, often accompanied by ichthyosis and other symptoms.
Key Characteristics
Hair Abnormalities
Patients with TTD typically have dry, short, and sparse hair. The hair often splits into small fibers due to compromised viscoelastic properties compared to those without the condition.Genetic and Cellular Insights
TTD encompasses several neuroectodermal disorders, all linked by defective synthesis of high-sulfur matrix proteins. Approximately half of TTD cases involve issues with nucleotide excision repair (NER) of UV-damaged DNA.There are three main categories of TTD based on cellular responses to UV damage and the affected genes. Most individuals have mutations in both alleles of the XPD gene. In UV-sensitive TTD patients, the TFIIH transcription factor?"needed for transcription initiation and DNA repair?"is impaired. This results in disrupted NER and decreased transcription of specific genes.
Physical and Neurological Features
Typically, TTD patients exhibit unique facial features, such as protruding ears and a receding chin, along with overall growth retardation. These symptoms, alongside neurological issues and brittle hair and nails, are linked to decreased RNA synthesis.Diagnosis and Examination
Microscopic Analysis
Under light microscopy, TTD hair might show irregular surfaces and diameters, mimicking conditions like trichorrhexis nodosa. When observed under polarized light, the hair displays a tiger-tail pattern, a feature recently noted in healthy infants as well.Reliable Testing
For accurate diagnosis, amino acid analysis measuring sulfur levels in hair remains a definitive test.In summary, Trichothiodystrophy is a complex condition with distinctive hair abnormalities and genetic markers, requiring specific tests for accurate diagnosis and study.
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