A point mutation at codon 210 (GTT to ATT) of the prion protein gene on chromosome 20 was found in a 48-year-old CJD-affected woman of a Chinese family. This affected woman had an early onset and long-duration form of CJD. Serial magnetic resonance image (MRI) analysis of this woman showed severe brain atrophy, prominent diffuse white matter degeneration, and subsequent mineralization of basal ganglia and thalamus. MR spectroscopy (1H) analysis elucidated the absence of peaks of choline, creatine and N-acetylaspartate. Using polymerase chain reaction and single-strand conformational polymorphism (PCR-SSCP) techniques, presymptomatic diagnosis of the second son of this woman showed that he has a similar codon mutation of prion gene as his mother.