A Unique Case of Renal Infiltration by Lymphoplasmacytic Lymphoma with Cast Nephropathy.

A 65-year-old male presented with dull pain abdomen, anorexia and weakness for 3 months. Cervical lymphadenopathy and moderate hepatosplenomegaly was present. Total leucocyte count were raised (49,440 cells/cmm) with marked lymphocytosis and atypical lymphocytes. Serum Creatinine was 2.74 mg/dl. Serum protein and albumin were 9.53 and 3.54 g/dl. Urine protein was 2.5 gm/day with inactive sediments. β2 microglobulin was 13,800 mcg/L. Serum free light chain assay showed Kappa/Lambda ratio of 77.56. No skeletal lesions were identified.

Among the differentials considered for the renal disease was lymphoma infiltration of kidney, favoured by presence of hepatosplenomegaly. However, non-nephrotic illness and lack of renal mass on radiology countered it. Myeloma cast nephropathy was considered due to renal dysfunction, anemia, reversed Albumin: Globulin ratio, non-albumin proteinuria and elevated β2 Microglobulin. However, it did not explain hepatosplenomegaly, lymphadenopathy, atypical lymphocytosis and non-existent bone lesions. Organomegaly and paraproteinemia suggested primary amyloidosis; but non-nephrotic presentation and elevated creatinine were against it.

Renal biopsy showed intense interstitial infiltrate of medium-sized atypical lymphoid cells, positive for CD-20 and negative for CD-3. CD-138 highlighted numerous plasma cells with Kappa restriction. Amyloid stains were negative. Bone marrow biopsy showed similar infiltration. Few renal tubular fractured hyaline casts were noted [Figure 1]. Lymphoplasmacytic lymphoma (LPL) with Kappa light chain cast nephropathy was diagnosed. The patient was treated with Bortezomib, dexamethasone and plasmapheresis. On one-month follow-up, significant reduction of serum creatinine (to 1.6 mg/dl), serum IgM and Kappa light chains was recorded.

Figure 1

Sections from renal biopsy showing (a) intense interstitial infiltrate of atypical lymphocytes (Periodic Acid Schiff, ×100); (b) CD20 positivity in atypical lymphocytes (Diaminobenzidine, ×200); (c) CD138 positivity highlighting plasma cells (Diaminobenzidine, ×200) and (d) Fractured renal tubular casts (arrows) (Periodic Acid Schiff, ×200)

LPL is a lymphoproliferative disorder characterized by lymphomatous infiltration of lymph nodes, hepatosplenomegaly and serum immunoglobulin M paraprotein. Renal infiltration is rarely seen.[1] Cast nephropathy though common in Multiple Myeloma is exceptional in LPL. Paraproteins are nephrotoxic and can cause acute kidney injury.[2] We report a unique case with renal infiltration by LPL with concomitant renal failure attributable to cast nephropathy. A single similar case was identified in Mayo Clinic archives over twenty years.[2] Renal biopsy is of utility in LPL in revealing cellular infiltration, tubulo-interstitial lesions, amyloid and non-amyloid glomerulopathy. Tubulointerstitial lesions herald the worst prognosis in LPL and could limit the renal response to haematological treatment.[2]

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Conflicts of interest

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