Is lupus a different disease in Indigenous Australians?

Lupus in Aboriginal and Torres Strait Islander Australians has a ‘distinct phenotype’ from that in non-Indigenous Australians, according to research from the Northern Territory.

A retrospective of 33 consecutive patients with biopsy-proven lupus nephritis between 2010 and 2019 comprised 26 Indigenous and seven non-Indigenous patients.

“Utilising the 2016 census data, the estimated incidence of lupus nephritis in Indigenous and non-Indigenous Australians of the Top End was 5.08 and 0.47 per 100,000 patient years respectively,” the study said.

Demographics and comorbidities were similar in both groups.

Indigenous patients were significantly less likely to present with cutaneous manifestations than other patients (23% v 71%; p=0.02) and had a trend to higher rates of haematological and neurological manifestations.

Laboratory tests showed the severity of proteinuria was greater, though not statistically significant, in Indigenous patients compared to the non-Indigenous patients.

“The presence of anaemia (77% vs 57%) and thrombocytopenia (35% vs 0%) were also more common among indigenous LN patients.”

In addition, the Indigenous Australian cohort also had a significantly lower platelet count (299 v 180 x 109/L; p<0.01) compared to non-Indigenous patients at the time of LN diagnosis.

A non-statistically significant lower mean serum C3 and C4 level were also observed in Indigenous Australians compared to non-Indigenous Australians.

Indigenous patients also had a higher incidence of positive anti-ribosomal P antibodies than non-Indigenous patients (57.69% v 14.29%; p=0.04).

“The reasons for the observed differences are not clearly understood. It may be multifactorial, involve a complex interplay between genetic factors and environmental triggers, occurring in a population with reduced nephron endowment and elevated renal disease vulnerability,” the investigators from Royal Darwin Hospital said.

“Geographical isolation and lack of culturally appropriate healthcare services, causing a delay in presentation and diagnosis, could also have contributed to the observed differences seen in disease severity.”

The study, published in the Internal Medicine Journal, said future research should be aimed at delineating the reasons for the observed differences.

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