P-ANCA IN MONOZYGOTIC TWINS WITH INFLAMMATORY BOWEL-DISEASE

Perinuclear antineutrophil cytoplasmic antibodies (P-ANCA) have been d emonstrated in patients with ulcerative colitis and in a higher freque ncy than expected in their first degree relatives. A hypothesis was pr oposed that P-ANCA is genetically determined and may represent a subcl inical marker of genetic susceptibility to ulcerative colitis. This st udy analysed P-ANCA in monozygotic twins with inflammatory bowel disea se to evaluate this hypothesis further. P-ANCA was analysed with indir ect immunofluorescence technique in 12 monozygotic twin pairs with ulc erative colitis and 14 twin pairs with Crohn's disease. Furthermore, t he study included 21 non-twin patients with ulcerative colitis, 18 non -twin patients with Crohn's disease, and 52 healthy controls matched f or sex and age. In ulcerative colitis P-ANCA occurred in nine of 14 (6 4.3%) monozygotic twins and in 13 of 21 (61.9%) non-twin cases, which was significantly different compared with healthy controls who were po sitive in three of 52 (5.8%) cases (p<0.0001). P-ANCA was found in two of 10 (20%) healthy twin siblings to twins with ulcerative colitis, w hich was not significantly different from healthy controls (p=0.18). T he results in Crohn's disease did not differ fi om healthy controls. P revious findings of P-ANCA occurring in ulcerative colitis but not in Crohn's disease are supported. This study does not support the hypothe sis that P-ANCA is a subclinical marker of genetic susceptibility to u lcerative colitis.