Islet cell and other organ-specific antibodies in U.S. Caucasians and Blacks with insulin-dependent diabetes mellitus.

Islet cell antibodies (ICA) were detected in 168 (33%) of 504 patients with insulin-dependent diabetes mellitus (IDDM). Mean age of onset of IDDM was 8.6 +/- 0.2 yr and mean age at testing was 13.4 +/- 0.3 yr. None of 162 controls without diabetes (mean age 21.8 +/- 0.9 yr) had ICA. Caucasian patients (404) had a 74% frequency of ICA within 3 mo of diagnosis and an overall ICA frequency of 36%. These results were similar to those reported from Europe. Black patients (100) had lower frequencies of ICA (P < 0.01) and thyroid antibodies (P < 0.05). Caucasian patients with onset of IDDM before 5 yr of age (107) had a lower frequency (P < 0.01) of ICA (21%) than those (297) with a later age of onset (42%). Patients with persistent ICA beyond 5 yr of IDDM had increased frequencies of gastric parietal and adrenal cortex cell antibodies. Thyroid microsomal antibodies were less frequent (P < 0.05) in blacks (4%) than in Caucasians (20%). The former did not have adrenal antibodies. Similar ICA frequencies among Caucasians with IDDM in the U.S. and in Europe suggest that etiologic factors are similar in the two geographic regions. The lower frequencies of ICA in patients with IDDM onset before 5 yr of age suggest that some of these patients may have a different etiology and/or a more rapid disappearance of islet cell antigens than patients with a later onset.l The lower ICA frequencies in black patients can be explained by heterogeneity of IDDM in this group and by admixture of IDDM susceptibility genes from the Caucasian genome to the black genome.