Hair shaft disorders

Key takeaways

• Hair shaft disorders are structural defects in the strand, either congenital or acquired. They fall into two large groups: those with fragility, where hair breaks easily, and those without (Giacaman 2022).
• If hair will not grow past a certain length, think breakage before shedding. Breakage-prone defects such as trichorrhexis nodosa look like thinning, but the follicle is fine (Rudnicka 2018).
• A gentle pull test and scalp microscopy (trichoscopy) are the key diagnostic steps, and trichoscopy has largely replaced light microscopy of plucked hairs (Bhat 2023; Rudnicka 2018).
• Curly and coily hair gets particular acquired problems, including acquired trichorrhexis nodosa, which is driven by hairstyling practices, alongside central centrifugal scarring alopecia and traction alopecia (Geisler 2024).
• Children with abnormal hair texture, or sparse or brittle hair, deserve evaluation. Shaft anomalies can be the first clue to a genetic syndrome, and any change in texture or growth should prompt assessment, including nails and teeth (Bhat 2023; Giacaman 2022).
• Treatment is mainly prevention and gentle handling. Congenital types need specialist assessment. Evidence quality is low, with reviews and case series and no randomized trials of cosmetic strategies.

What the strand looks like

Scalp microscopy findings summarized in a 2018 review (Rudnicka 2018):

Congenital types often present in infancy and may be tied to syndromes. Acquired types usually arise from repeated physical or chemical stress on the shaft. The curve of a tightly coiled strand creates mechanical stress points, and hairstyling practices likely contribute to acquired trichorrhexis nodosa and traction alopecia in curly hair, while the evidence for relaxers and heat in CCCA is mixed (Geisler 2024).

Hair type notes

• Curl 3A to 4C is most at risk of acquired trichorrhexis nodosa from dry combing, tight styling and relaxers combined with heat. Detangle when wet with conditioner using fingers or a wide-tooth tool (see brushing and detangling and traction and hairstyles).
• Fine strands break at lower force, and high-porosity strands show lifted cuticles (see hair porosity).
• Straight or wavy thick hair usually shows cosmetic split ends and fraying from heat or bleach, not congenital disease.
• Split ends cannot be repaired, only temporarily bonded or cut (see bond builders).

Bottom line

Do a gentle pull test on a small section; many broken short hairs of varied lengths suggest breakage rather than shedding. Lower the mechanical and thermal load: less tension, less heat, no combing when dry, and no overlapping chemical treatments. Persistent brittle hair since childhood that gentle care does not fix, or any child with sudden brittle or sparse hair, warrants a dermatologist; bring a hair sample if possible. See when to see a dermatologist. Discuss with a doctor.