What deficiency causes brittle hair
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Causes of Brittle Hair: Sulfur and Methionine Deficiency
Sulfur Deficiency in Trichothiodystrophy (TTD)
Trichothiodystrophy (TTD) is a primary condition associated with brittle hair due to sulfur deficiency. TTD is a group of autosomal recessive disorders characterized by short, brittle hair with low sulfur content 135. The hair abnormalities in TTD are due to defective synthesis of high-sulfur matrix proteins, which are crucial for hair strength and integrity 13. This deficiency in sulfur-rich proteins leads to the distinctive brittle hair seen in TTD patients 35.
Methionine Deficiency and Hair Brittleness
Another potential cause of brittle hair is methionine deficiency. Methionine is an essential sulfur-containing amino acid. A case study of an 8-year-old girl with brittle, short, and sparse hair revealed that her hair was completely devoid of methionine, although it had a normal cystine content . This suggests that methionine deficiency could play a role in hair brittleness, although this specific cause has not been widely documented or studied .
Structural and Molecular Abnormalities
The structural integrity of hair in TTD patients is compromised at multiple levels. Microscopic examinations reveal alternating light and dark bands, known as the "tiger tail" pattern, and numerous surface irregularities 39. These structural abnormalities make the hair excessively prone to breakage and weathering . Additionally, scanning electron microscopy has shown severe cuticular defects in the hair of TTD patients 29.
Genetic and Molecular Mechanisms
The genetic basis of TTD involves mutations in genes responsible for DNA repair and basal transcription, such as the XPB and XPD genes 14. These mutations lead to defects in the nucleotide excision repair (NER) pathway and basal transcription, contributing to the clinical features of TTD, including brittle hair 14. The TTD mouse model has been instrumental in understanding these genetic and molecular mechanisms, reflecting many of the human disorder's features, including brittle hair and developmental abnormalities .
Conclusion
Brittle hair can be caused by deficiencies in sulfur and methionine. In conditions like Trichothiodystrophy, the deficiency in sulfur-rich proteins due to genetic mutations leads to brittle hair. Methionine deficiency, although less documented, also appears to contribute to hair brittleness. Understanding these deficiencies and their underlying mechanisms is crucial for diagnosing and managing hair disorders effectively.
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