Renal disease patterns in aboriginal Australians. A family-based study in a high incidence community.

OBJECTIVES: To explore the apparent excess of renal disease in a coastal Aboriginal community in the Northern Territory and to explore its familial basis. DESIGN: Families were ascertained through probands with significant proteinuria. Controls were selected from unrelated subjects living with these families. PARTICIPANTS: All surviving grandparents, parents, siblings, children and grandchildren of 16 probands were studied; there were 219 participants in all, including 58 adult control subjects. MAIN OUTCOME MEASURES: Anthropometric data included the body mass index (BMI), and resting blood pressure. Urinary protein and creatinine levels were measured and urine was examined microscopically for glomerular haematuria (more than 10 red blood cells per microL, with at least 20% dysmorphic red cells). Two hours after a 75 g glucose drink, venous blood was taken and analysed for biochemical markers including urea, creatinine, glucose and gamma-glutamyltransferase. RESULTS: Significant proteinuria (protein to creatinine ratio greater than 50 mg/mmol), provided evidence of renal disease in 30% of both case relatives and control subjects. The prevalence of proteinuria was associated with increasing age, increasing diastolic blood pressure, increasing glucose level and female sex. However, two contrasting groups of subjects were identified in that relatives of probands had more glomerular haematuria than controls (27/112 v. 3/58, P = 0.005) and this was most marked in a family with multiple probands and in the parents of probands; in contrast, controls were more likely to have hypertension and obesity. Diabetes was highly prevalent in adult study subjects (12.4%) with no difference between controls and relatives of probands. CONCLUSIONS: The very high prevalence of renal disease in Australian Aborigines parallels the situation in American Indian communities undergoing rapid cultural change. In the island Aboriginal community studied, proteinuria and glomerular haematuria are familial, possibly due to genetically influenced glomerulonephritis evoked by (unknown) environmental factors. Proteinuria associated with obesity, hypertension and diabetes is less obviously familial, and plausibly related to poor nutrition and other lifestyle factors. The high prevalence of proteinuria and other risk factors in community-based studies and the high incidence of end-stage renal disease show that there is an urgent need for effective education and prevention programs, for more active treatment of hypertension, and for further work to clarify the aetiology and pathogenesis of renal disease in Aboriginal communities.

Streptococcal infection and renal disease markers in Australian aboriginal children.

OBJECTIVE: To demonstrate an association between markers of streptococcal infection and markers of glomerulonephritis in Aboriginal children. DESIGN: A cross-sectional study of Aboriginal children of school age. SETTING: Three Aboriginal communities in the Northern Territory--two, coastal and one, desert. PARTICIPANTS: Sixty children, randomly selected from the school roll, were studied in each community; thus there were 180 children in total, aged 5-17 years. Midstream urine and venous blood was collected and swabs were taken from the pharynx and from impetiginous skin lesions or axillary skin in the absence of impetigo. Clinical records were examined for evidence of past glomerulonephritis. MAIN OUTCOME MEASURES: Swabs were cultured for beta-haemolytic streptococci and isolates were grouped; serum was tested for titres of antistreptolysin O (ASO) and antideoxyribonuclease B (anti-DNaseB). Protein and creatinine levels were measured in urine, and a ratio of protein to creatinine (UPC) of more than 50 mg protein per mmol creatinine was taken as a measure of significant proteinuria. Urine was examined microscopically for glomerular haematuria (greater than 10 red blood cells per microL with at least 20% dysmorphic red cells). RESULTS: Group A beta-haemolytic streptococci were isolated from the throat swabs of two children and from skin swabs of 25 (13.9%) children; 20 of these were from impetiginous lesions and five from normal axillary skin. beta-Haemolytic streptococci of group C or G were grown from the throat swabs of 13 (8.1%) children. The median titre of ASO (256 IU) was raised compared with a reference level, and the median titre of anti-DNaseB (3172 IU) was particularly high; ASO titres were significantly higher in 31 children with impetigo than in 149 children without impetigo. Significant proteinuria was present in 7 (3.9%) children and glomerular haematuria in 16 (8.9%). Glomerular haematuria was present in 2/7 (28%) children with proteinuria, 4/21 (19%) children with a past history of post-streptococcal glomerulonephritis, in 5/31 (16%) of those with impetigo and in 4/25 (16%) of those with positive skin cultures. However, none of these prevalences was significantly greater than the prevalence of glomerular haematuria among the other children. The prevalence of proteinuria differed significantly between communities and increased significantly with age. Furthermore, the differences in childhood proteinuria observed between communities in this study were parallel with community differences in the prevalence of proteinuria in a related study of adults. CONCLUSIONS: Group A streptococci are important causes of impetigo in Aboriginal children. Streptococcal skin infection may contribute to glomerular haematuria, proteinuria and persistent glomerulonephritis in Aboriginal children, and possibly to chronic glomerulonephritis in adult life. Public health programs are needed to reduce the prevalence of impetigo and group A streptococcal infections in Aboriginal communities; longitudinal studies are needed to test the relationship between streptococcal skin infection in Aboriginal children and chronic renal disease in later life.