[Renal involvement in sarcoidosis: Prognostic and predictive factors]

Sarcoidosis 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 during sarcoidosis.

It's a retrospective study including 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 by following their evolution: group A (n=26) represents those with renal remission or deterioration of renal function but without progression to end-stage renal disease and group B (n=8) those with progression to end-stage renal disease. To detect the predictive factors of end-stage renal 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 impairment followed in our department during the same period (group 2).

Renal involvement was observed in 34 patients hospitalized for sarcoidosis (43.6%). There were 28 women and 6 men with a sex ratio of 0,21. The mean age at diagnosis of sarcoidosis was 47.1 years. The median time from sarcoidosis diagnosis to renal disease 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 noted in 25 patients (73.5%). Corticosteroid therapy was initiated in 33 patients (97%) associated with immunosuppressive therapy in 3 cases. Predictive factors of end-stage renal disease were advanced age at diagnosis of nephropathy (P=0.007), comorbidities (P=0.002), multi-organ involvement (P=0.041), initial renal failure (P=0.013), interstitial fibrosis (P=0.006) and renal granulomas (P=0.007). Predictive factors of renal impairment during sarcoidosis were multi-organ involvement, inflammatory syndrome and hypercalcemia.

Renal envolvement, although rare during sarcoidosis, can influence the prognosis hence the great interest of its early detection to prevent progression to end-stage renal failure.