MO137: Sarcoidosis in a Living Kidney Donor Candidate: Case Report and Review of the Literature
Authors: Mori Giacomo , Tei Lorenzo , Alfano Gaetano , Fontana Francesco , Magistroni Riccardo , Donati Gabriele 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Sarcoidosis (SCD) is a granulomatous disease that mostly affects young adults, presenting with hilar adenopathy, lung reticular opacities and skin/joint/eye lesions. Incidence varies in Europe between 0.3% and 1.5%, higher in southern countries. Up to one-third of patients have extrathoracic manifestations.
Renal involvement varies among different case series. Despite a prevalence of about 13% in autopsies on systemic SCD affected individuals, it is clinically evident in 0.7–4.3% of patients, with a reduced glomerular filtration rate associated with mild or absent urinary anomalies. It usually presents as a tubulointerstitial nephritis at kidney biopsy. Noncaseating granulomas are typical but not always present. Renal injury can also derive from hyperkalcaemia and hypercalciuria (secondary to vitaminD production in granulomas), which cause nephrocalcinosis or nephrolitiasis. A clinical presentation with hyperkalcaemia associates to a better response to therapy (prednisone 1 mg/kg/day for 6–12 weeks, tapered in 6–9 months). An Italian survey on SCD acute kidney injury (AKI) described female sex, hyperkalaemia and absence of granulomas at biopsy as positive prognostic factors, without any correlation between proteinuria and histological damage. SCD AKI evolved to CKD in over 60% of cases (37.5% without comorbidities at onset), with a mean GFR slope of 5 mL/min/year when granulomatous interstitial nephritis was present.

METHOD
We describe the case of a 55-year-old male, who proposed as a living kidney donor for his wife. His clinical history included a paranoid episode 20 years before, compensated and on psychiatric follow-up at the moment of the screening, dyslipidaemia and normal blood pressure.

RESULTS
Preoperative screening showed a renal function just above safety threshold for donation (cystatin C-creatinine CKD-EPI 80 mL/min/1.73 m2), a normal urinary sediment and no proteinuria. A thoracic and abdominal CT scan (Figure 1) described numerous aorto-caval adenopathies, stable at a second CT after 3 months. Lungs were unaffected, kidneys and the urinary tract were regular, without calcifications or stones.
No infection was detected (negative QuantiFERON, HIV, EBV &lt;1000 copies/mL), suggesting a differential diagnosis between lymphoma and SCD. Serum and urine electrophoresis, immunofixation, light chains, Bence Jones and peripheral blood lymphocyte typing were checked in parallel to ACE dosing; 24-h urine calcium, calcemia, vitamin D, dermatological and ocular examination all normal. An endobronchial ultrasound biopsy was performed, after a PET (Figure 2) to identify the targets with the highest SUV (3.9–6.7). Histology described normal lymphocytes, noncaseating granulomas with sarcoidosis epithelioid histiocytes.

CONCLUSION
Stage 1 pulmonary SCD without clinical renal involvement was confirmed. Although in a single case of living kidney donation from SCD affected subject was reported, data on GFR deterioration in the long term are lacking. Considering the baseline renal function of the potential donor and the not-quantifiable risk of future AKI, we decided to deem him unfit for donation, despite the absence of markers of disease activity at the moment of the screening. Kidney biopsy will be considered in the future in case of urinary abnormalities or GFR deterioration.