A 3 1/2-year-old haemophilic child, repeatedly transfused with blood products, developed pemphigus foliaceus with presence in serum of both intercellular and anti-cytomegalovirus antibodies at high titre. The locus A26, which seems to be a genetic marker of pemphigus, was detected in his haplotype. Cytomegalovirus infection of transfusional origin is suspected to have triggered the outbreak of pemphigus.