Renal involvement in sarcoidosis: Prognostic and predictive factors

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IntroductionSarcoidosis is a systemic granulomatous disease that primarily affects the respiratory system and lymphatic vessels. Renal involvement is rare, poorly studied, and found in less than 10% of cases. The objective of our study was to identify factors of poor renal prognosis and predictive factors of renal involvement in sarcoidosis.MethodsThis was a retrospective study that included patients hospitalized in our department for sarcoidosis with renal involvement over a period of 40 years. To study renal survival, we identified two groups of patients with renal manifestations of sarcoidosis based on their disease course: group A (n=26) represented those with renal remission or deterioration of renal function but no progression to end-stage kidney disease, and group B (n=8) those who progressed to end-stage kidney disease. To identify the predictive factors of end-stage kidney disease in patients with sarcoidosis, we compared the clinical and paraclinical characteristics of our patients (group 1) to those of 44 patients with sarcoidosis without renal involvement who were followed up in our department during the same period (group 2).ResultsRenal involvement was observed in 34 patients hospitalized for sarcoidosis (43.6%). There were 28 women and 6 men, with a male/female ratio of 0.21. The mean age at diagnosis of sarcoidosis was 47.1 years. The median time from sarcoidosis diagnosis to renal involvement was 2 months (range 1–72). Tubulointerstitial nephropathy was the most frequent renal manifestation, observed in 24 patients (70.6%). Hypercalcemia and hypercalciuria were found in 52.9% and 46.4% respectively. Renal failure was observed in 25 patients (73.5%). Corticosteroid therapy was initiated in 33 patients (97%), combined in 3 cases with immunosuppressive therapy. The predictive factors of end-stage kidney disease were advanced age at time of nephropathy diagnosis (p=0.007), comorbidities (p=0.002), multi-organ involvement (p=0.041), renal failure at the time of sarcoidosis diagnosis (p=0.013), interstitial fibrosis (p=0.006), and renal granulomas (P=0.007). The predictive factors of renal involvement in sarcoidosis were multi-organ involvement, raised inflammatory markers, and hypercalcemia.ConclusionAlthough rare, renal involvement in sarcoidosis, can influence the prognosis. It is therefore important to detect it early in order to prevent progression to end-stage kidney disease.