Clinicopathological features for the prediction of immunosuppressive treatment responses in sarcoidosis-related kidney involvement: a single-center retrospective study

Background/aim: Sarcoidosis is a multisystem disorder that affects many organs, including the kidneys. This single-center retrospective study investigated the clinical, pathological, and laboratory findings of patients with kidney sarcoidosis who were treated with immunosuppressives.

Materials and methods: Twenty-three patients with biopsy-confirmed kidney sarcoidosis were included. Demographic, clinical, pathological, and laboratory findings, in addition to the treatments and outcomes of 20 patients with at least one month of follow-up were evaluated.

Results: The median age of the patients at the time of biopsy was 47 years (60.9% were female). The median baseline estimated glomerular filtration rate (eGFR) and proteinuria were 21.5 mL/min and 1 g/g or g/day, respectively. Nineteen of the 23 patients were diagnosed with nonglomerular disease (four had glomerular diseases). Extrarenal sarcoidosis was present in 86.7% of the patients. Granulomatous interstitial nephritis (56.5 %) and nephrosclerosis with intratubular calcific casts (17.4 %) were the two most common diagnoses. All the patients initially received 1 mg/kg/day steroids for kidney involvement. Although no statistical difference was observed in kidney function during the follow-up, steroids improved the eGFR in the first month compared with baseline in patients with nonglomerular diseases (p = 0.049). Eventually, 45% of the patients developed end-stage kidney disease, and 45% of cohort had a treatment response. Patients with higher baseline calcium levels (p = 0.03) and lower degrees of interstitial fibrosis/tubular atrophy (p = 0.043) had better kidney outcomes. Moreover, none of the patients with sarcoidosis-related secondary glomerular disease had a treatment response (p = 0.043).

Conclusions: Hypercalcemia and lower interstitial fibrosis and tubular atrophy rates might be associated with better outcomes in sarcoidosis-related kidney involvement under immunosuppressive treatment. Moreover, late diagnosis, irregular follow-up, and glomerular disorders could be poor prognostic factors.