The Value of Studying Clinical and Serologic Phenotypes in North American Native Populations with Autoimmune Disease

Systemic sclerosis in Native Americans of the American Southwest

“…Previous reports of SSc in populations of African, Han Chinese, Mahgreb, Arab, and Thai descent have demonstrated a higher incidence of SSc, earlier age of onset, and greater severity compared with‐European descent populations 2–9 . Similarly, certain reports of Native Americans with SSc from different areas of North America also found an earlier SSc onset, more diffuse disease, a greater burden of gastrointestinal complications, and more frequent Raynaud phenomenon compared with non‐Native cohorts, findings between Native Americans and non‐Natives were not confirmed in the present study 8–20 . However, not all indigenous peoples have been reported to have more severe disease than Caucasian populations.…”

“…The present results in Native Americans with SSc from the American Southwest are also similar to certain previous reports regarding other Native American populations with SSc from the USA and Canada 8–11 . Studies of Native Americans in southeastern Oklahoma found 65% of patients had diffuse cutaneous SSc very similar to the present findings of 57.1% again supportive of similarities between Native Americans of different regions 8 .…”

“…Gastrointestinal involvement affects 90% of patients with SSc, making it the most frequent internal complication; it occurs in those with limited and with diffuse cutaneous SSc, and was also dominant in the present Native American cohort 8–20,30,34 . Studies have shown that severe gastrointestinal involvement, defined as malabsorption, multiple episodes of pseudo‐obstruction, and/or severe problems requiring hyperalimentation, occurs in 8% of patients with SSc, and is associated with high mortality (15% of patients survive after 9 years) 30,34,35 …”

“…However, certain end‐organ involvement was worse in the present Native American SSc cohort compared with the Canadian Native American cohort including severe GERD (US 100% [28/28] vs Canada 74.6% [47/71]; P < .001) and pulmonary arterial hypertension (estimated RVSP >45 mm Hg: US 35.7% [10/28] vs Canada 8.5% [5/71]; P = .001), indicating some differences between the Canadian and American Native American SSc cohorts, possibly due to genetics, environmental exposures, or altitude 1,23 . As these same characteristics and outcomes in Native Americans from the American Southwest were similar to those in non‐Natives from the same region, one could postulate a dominant effect of local environmental exposures and especially altitude between the different regional Native American SSc cohorts 8–20,23 . Indeed Dubroff et al have found that in New Mexico, there is a strong association between pulmonary arterial hypertension prevalence and residence at altitude above 1219 m (4000 ft) (OR 26.6, 95% CI 8.5‐83.5; P < .001), which is entirely consistent with increased prevalence of pulmonary arterial hypertension reported in the present report 23 …”

“…Native American communities in discrete areas have been reported to have the highest prevalence of SSc in any human population with a prevalence of 469 cases/100 000 population compared with 1.2‐25.6/100 000 in non‐Native Americans (henceforth, non‐Natives) 8 . The severity and mortality of Native Americans with SSc and other autoimmune diseases has also been reported to be higher, presumably from more severe disease and disparities in health care 8–18 . Beyond studies of Native American populations in Oklahoma, Alaska, the American Northwest, and Canada, the manifestations of SSc in Native Americans in other regions, in particular the American Southwest, are less well described but are equally important for healthcare planning in these communities and for understanding manifestations and variability of SSc in different human populations 8–18 .…”