Trichothiodystrophy leading to generalized trichorrhexis nodosa-like hair changes with abnormal hair breakage is described in a 4-year-old girl. A marked deficiency of sulphur and the sulphur-containing amino acid, cystine, was detected in the biochemical analysis of the hair. Further investigation of the hair showed the morphological criteria of trichothiodystrophy. Commonly related symptoms, such as mental retardation, ichthyosis and increased sensitivity to sunlight, were not present in our patient.