Kidney Involvement in Rosai-Dorfman Disease: A Rare Case of Acute Tubulointerstitial Nephritis

Introduction: Rosai-Dorfman-Destombes disease (RDD) is a rare non-Langerhans cell histiocytosis with lymphadenopathy, and has an unknown etiology. In extra-nodal manifestations, kidney involvement is rare, only observed in 4% of cases, and is associated with a poor prognosis. Kidney manifestation usually is a hilar mass, while parenchymal involvement without mass is extremely uncommon. Case Description: A 50-year-old male with a previous diagnosis of RDD, was referred to the emergency department after a routine follow-up revealed an elevated creatinine. He reported intermittent right-sided flank pain for two weeks and occasional nausea over the previous three days. Past medical history included hypertension, type 2 diabetes mellitus, and alcohol use disorder. On physical examination, he was hemodynamically stable but was noted to have right costovertebral angle tenderness. Labs showed creatinine 3.8 mg/dL (baseline of 1.2 mg/dL, 3 months prior), blood urea nitrogen (BUN) 44 mg/dL, estimated glomerular filtration rate (eGFR)18 mL/min/1.73m2, and low C3 and C4 levels. Kidney ultrasound demonstrated bilaterally enlarged kidneys with mild parenchymal heterogeneity. Kidney biopsy results revealed severe, nearly diffuse tubulointerstitial nephritis (TIN) composed of predominantly histiocytes. Immunohistochemistry showed histiocytes strongly positive for S100, CD68, and CD163, and negative for CD1a, consistent with kidney involvement by RDD (Figure 1). Treatment with prednisone 60 mg daily was initiated for the patient, and after one month, creatinine decreased to 1.56 mg/dL, and eGFR increased to 53 mL/min/1.73m2, followed by a gradual taper of prednisone. Discussion: Acute TIN associated with RDD is a very rare but serious condition. Monitoring kidney function, early recognition, and histopathologic confirmation of S100/CD68-positive and CD1a-negative histiocytes are essential for timely diagnosis and initiation of therapy to preserve kidney function.