IgG subclasses in pemphigus in Indian and UK populations.

The autoimmune blistering disease pemphigus is more common in the Indian subcontinent than in the UK. This study of 19 patients from Oxford, UK and 39 patients from New Delhi, India demonstrates that the incidence of the disease subtypes is different in the two countries. In the UK the commonest subtypes are pemphigus vulgaris and foliaceus with equal prevalence (both eight of 19), but in India pemphigus vulgaris is the most frequent (31 of 39), while pemphigus foliaceus is uncommon (three of 39) and with equal prevalence to the other subtypes. These populations also differ with a younger age at onset in the Indian patients (36.9 India; 52.7 UK) though the sex distribution is the same. Study of the immunopathology shows that the antibodies produced by patients in the two countries do not differ significantly, and are predominantly of the IgG4 subclass. The antibody produced does not vary with the subtype of pemphigus or the age or sex of the patient. Although there are considerable differences between the two groups of patients this difference is not reflected by the subclass of auto-antibody response.