Trichorrhexis may have a genetic basis but appears to be precipitated by environmental factors. Among African Americans, the hair may appear not to grow but microscopic examination shows that the hair shafts have nodes or swellings near the scalp which fracture easily. The hair actually grows but is broken before it can become long. Among whites the defect often appears at the ends of the hair shaft with splitting of the ends, thinning and whitish discoloration.
These conditions are directly related to environmental causes such as "perming", blow drying, aggressive brushing, and excessive chemical exposure.
In some cases, trichorrhexis nodosa may be caused be an underlying disorder such as argininosuccinicaciduria, Menkes' kinky hair syndrome, Netherton's syndrome, hypothyroidism, or trichothiodystrophy.
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