Table 1.
COMPARISON OF FEATURES OF XERODERMA PIGMENTOSUM, TRICHOTHIODYSTROPHY AND COCKAYNE SYNDROME
| FEATURE | XERODERMA PIGMENTOSUM (XP) |
XP WITH NEUROLGIC ABNORMALITIES |
TRICHOTHIO- DYSTROPHY (TTD) |
COCKAYNE SYNDROME (CS) |
XP/CS COMPLEX |
|---|---|---|---|---|---|
| SKIN | |||||
| Skin sun sensitivity | yes | severe | yes / no | yes | yes |
| Lentiginous skin pigmentation | yes | yes | no | no | yes |
| Sunlight - induced skin cancer | yes | yes | no | no | yes |
| EYES | |||||
| Photophobia | yes | yes | yes/ no | yes | yes |
| Conjunctival growths | yes | yes | no | no | yes |
| Cancer (anterior eye / lids) | yes | yes | no | no | not reported |
| Congenital cataracts | no | no | yes | yes | no |
| Pigmentary retinal degeneration | no | no | no | yes | yes |
| SOMATIC | |||||
| Short stature | no | no / yes | yes | yes | yes |
| Immature sexual development | no | no | no / yes | yes | yes |
| NERVOUS SYSTEM | |||||
| Progressive sensorineural deafness | no | yes | no | yes | yes |
| Developmental delay | no | yes | yes | yes | yes |
| Progressive neurological degeneration | no | yes | unknown | yes | yes |
| Primary neuronal degeneration | no | yes | no | no | no |
| Dysmyelination of brain | no | no | yes | yes | yes |
| Cerebral atrophy | no | yes | no/ yes | yes | yes |
| Cerebellar atrophy | no | yes | no | yes | yes |
| Calcifiation (basal ganglia) | no | no | no/ yes | yes | yes |
| DISEASE MECHANISM | |||||
| Reaction to exogenous or endogenous DNA damaging agents | yes - severe | yes - severe | no | yes | yes |
| Developmental defect | no | yes | yes - severe | yes - severe | yes - severe |
| Nucleotide excision repair defect | yes | yes | yes | yes | yes |
| Molecular defects | XPA, XPC, XPD, XPE, XPF, XPG, XP VARIANT (POLH) | XPA, XPB, XPD, XPF, XPG | XPB, XPD, TTDA, TTDN1 | CSA, CSB | XPB, XPD, XPG |