IgA Nephropathy in the Triethnic Population of New Mexico

Aims: IgA nephropathy (IgAN) is the most frequent glomerulonephritis around the globe, but its incidence in the United States is unknown. The disease has a preponderance for certain racial/ethnic groups. Our goals were to retrospectively analyze a series of IgAN biopsies from the state of New Mexico and to calculate an estimated incidence. Then we compared the racial/ethnic composition of our patient cohort to the composition of the New Mexico population and examined the three main racial/ethnic groups for differences in clinical and pathologic parameters.

Materials And Methods: Renal biopsies and clinical data from IgAN cases newly diagnosed in New Mexico between 2000 and 2005 were reviewed. We compared the racial/ethnic composition of our patient cohort to the demographic composition of the New Mexico population. Demographic, clinical, and histopathologic variables were analyzed with respect to the patients' race/ethnicity.

Results: The incidence of IgAN in New Mexico was 10.2 cases per million persons per year (9.3 when Henoch-Schönlein purpura cases were excluded). American Indians were twice as frequent in our patient cohort when compared to their demographic representation, with the reverse finding for Non-Hispanic Whites. Hispanics more frequently had nephrotic range proteinuria than Non-Hispanic Whites and American Indians. On renal biopsy, endocapillary proliferative glomerulonephritis was the most common glomerular abnormality, followed by the focal segmental glomerulosclerosis (FSGS)-like pattern. The FSGS-like pattern was more frequent in American Indians and Hispanics than in Non-Hispanic Whites.

Conclusions: This is the first report of an incidence figure of IgAN for an entire state in the US. American Indian and Hispanic patients had a stronger representation in our cohort than Non-Hispanic Whites, when compared to the general New Mexico population.