The goal of this research is to study the associations of genetic variants of gout and kidney failure, which are very common in the Melanesian population in New Caledonia

Gout is a chronic pathology linked to the deposition in the tissues of monosodium urate (MSU) crystals, secondary to hyperuricemia (high blood levels of urate). Gout causes very painful joint attacks that are first acute and then lead to chronic pain, and disabling deforming manifestations called tophus. The disease is strongly associated with cardiovascular comorbidities and chronic renal failure.

In New Caledonia, the prevalence of chronic kidney disease (CKD) (according to the glomerular filtration rate (GFR) < 60 ml/min) was of 7.4% in 2015 (according to the epidemiological study "Barometer Health 2015"). In the Loyalty Islands, which has overall significantly more Melanesian population, a local database showed that in 2018 the prevalence of patients having at least one blood test reporting kidney disease (GFR CKD< 60 ml/min) and seen at least once in the previous two years was as follows:

• 7.7% in Lifou (9,200 inhabitants)
• 8.4% in Maré (5,700 inhabitants)
• 9.1% in Ouvéa (3,400 inhabitants) In summary, inflammatory diseases such as CKD and gout have high prevalence in New Caledonia and the Loyalty Islands, and constitute a major health issue. Although the high prevalence of these diseases is probably due in part to non-genetic factors (environment, diet, etc.), it is likely, given the demographic history of this region, that undetected genetic risk alleles among the Melanesian population contribute to the appearance and progression of diseases. Performing genetic and epidemiological studies in an as yet understudied region is essential to identify these variants, which could lead to improved diagnoses and health outcomes.

Inclusion Criteria:

Criteria common to the 3 cohorts :

- Consenting to participate in the study and having signed the informed consent

- Claiming to be of Melanesian ethnicity

1. Patients with gout :

   • Age: 18 - 70 years old

   • To be included in the study, a patient with a diagnosis of gout in his medical file or declaring to have gout will have to satisfy to the ACR/EULAR (ref) classification criteria :

     1. have had at least one episode of swelling, pain spontaneous, or triggered by pressure, of a joint peripheral or a bursa AND evidence of sodium urate crystals in a joint or bursitis symptomatic or by puncture of a tophus reported in his medical file.
     2. Or Score > or =8 according to ACR/EULAR clinical criteria

2. Patients with CKD

   • Age: 18 - 70 years old

   • Patients on dialysis or CKD clinically diagnosed on the basis of:

     1. Markers of kidney damage (one or more) : Albuminuria (ACR ≥ 30 mg/g), Urinary sediment abnormalities (e.g., casts urinary), Electrolyte abnormalities and other, abnormalities due to tubular disorders (eg, hyperkalemia), abnormalities detected by histology, structural abnormalities detected by imaging (e.g.,USG), history of kidney transplantation
     2. Decreased kidney function: GFR < 60 ml/min/1.73 m² (calculated according to the Chronic Kidney Disease - EPIdemiology formula: CKD-EPI)

3. Controls cohort

   • Absence of gout or CKD
   • Age: 30 - 80 years old

Exclusion Criteria:

• Pregnant women
• Individuals under guardianship / curatorship / judicially incapacitated