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hair:
| • | from Greek tricho, hair _+ thio, sulfur + dys, faulty + trophe, nourishment |
| • | important clinical marker = hair with markedly reduced sulfur (amino acid = cysteine)content |
| • | under microscope – trichoschisis (clean fractures) |
| • | under polarized light – “tiger tail hair” |
| • | grossly – short sparse brittle hair |
clinical:
| • | = a group of disorders; autosomal recessive |
| • | (P)IBIDS – (Photosensitivity), Ichthyosis, Brittle hair, Intellectual impairment, Decreased fertility, Short stature |
| • | (the subgroup that overlaps with XP has a mutation in the basal transcription factor TFIIH – this factor plays a role in nucleotide excision repair) |
| • | ddx: CIE, lamellar ichthyosis, Netherton’s syndrome |
Trichothiodystrophy = “tiger tail hair” under polarized light
vs.
Pili annulati = alternating areas of light (normal) and dark (gas-filled) hair under normal light microscope
mnemonic:
| • | at the trichothiodystrophy zoo: they tried to give sulfur to the tigers and the polar bears, but it caused decreased fertility, and the children they finally had (named PIBIDS and IBIDS) had short stature and intellectual impairment |
see Ichthyoses, Hair Shaft Abnormalities
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