IgA nephropathy in the triethnic population of New Mexico

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.

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.

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.

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.