Clinical features and course of type A and type B vitiligo.

Four hundred and eighty one cases of vitiligo (acquired idiopathic depigmentation) were studied clinically. They were divided into two types, type B, in which depigmented patches are confined to a definite dermatome in the same manner as herpes zoster, and type A, which included all cases of vitiligo not classified as type B. The ratio of type A:type B was approximately 3:I. Onset of type A vitiligo could occur at any age, whereas type B generally affected the young. The activity of type B vitiligo usually ceased after one year, following rapid spread over the particular dermatomal area. However, in type A vitiligo new depigmented patches continued to appear throughout the patients' lives. Association with halo naevus and Köbner's phenomenon were observed exclusively in type A. Association with diseases with a proven or suggested allergic or immunological aetiology was more often found in type A. These findings support our hypothesis that type A and type B vitiligo have a different pathogenesis and that autoimmune mechanisms play a role only in type A.