Dysproteinemia-related nephropathy associated with crystal-storing histiocytosis

Abstract

CASE PRESENTATION A 41-year-old white man presented with a 6-month history of worsening neck pain accompanied by 20Ib weight loss. He was initially referred to an orthopedic surgeon and work-up including magnetic resonance imaging revealed shoulder bursitis for which he received a steroid injection. However, neck pain continued and laboratory tests revealed anemia and renal insufficiency, leading to his referral to an internist. The patient had no significant past medical history or family history of renal disease and he was not taking any medications. Physical examination revealed temporal wasting but was otherwise unremarkable. Laboratory investigations revealed the following: blood urea nitrogen 32 mg/dl (normal 7-25 mg/dl), serum creatinine 4.2 mg/dl (normal 0.5-1.4 mg/dl), serum calcium 9.8 mg/dl (normal 8.5-10.4 mg/dl), phosphorous 4.3 mg/dl (normal 2.5-4.5 mg/dl), sodium 143mmol/l (normal 135-146 mmol/l), potassium 3.6mmol/l (normal 3.5-5.3 mmol/l), chloride 109 mmol/l (normal 98-110 mmol/l), bicarbonate 17 mmol/l (normal 21-33 mmol/l), glucose 95 (normal 65-139 mg/dl), lactate dehydrogenase 505 (normal 105-333 IU/I), white blood cell count 9800/μl, hemoglobin 9.7 g/dl, hematocrit 28.3%, and platelet count 316000/μl. Erythrocyte sedimentation rate was markedly elevated (>100mm/h). Total serum protein was 8.8 g/dl (normal 6.0-8.3 g/dl), serum albumin was 4.2 g/dl (normal 3.5-4.9 g/dl), and β2-microglobulin was elevated (10.7 mg/l, normal < 1.85 mg/l). Quantitative serum immunoglobulins (Ig) revealed elevated IgD (842 mg/dl, normal 0-14 mg/dl) and decreased levels of IgG (450 mg/dl, normal 694-1618 mg/dl), IgA (32 mg/dl, normal 81-463 mg/dl), and IgM (9.9 mg/dl, normal 48-271 mg/ dl). Serum protein electrophoresis revealed a monoclonal spike (0.82 g/dl) with IgD kappa (κ) specificity, elevated free K light chains (81 200 mg/l, normal range 3.3-19.4 mg/l), and normal level of lambda (λ) light chains (10.6 mg/l, normal range 5.7-26.3 mg/l). Urinalysis revealed 100mg/dl glucose; these findings, together with the normal serum glucose, normal serum phosphate, and low serum bicarbonate levels, suggested partial Fanconi's syndrome. Urinalysis also revealed 1 + protein; however, 24-h urine collection contained 20.2 g protein of which 13.975 g (69.2%) consisted of free K light chains. Bone marrow examination revealed diffuse infiltration by IgD K-positive plasma cells, accounting for 50% of overall cellularity, consistent with multiple myeloma. Based on the finding of significant urinary light chain excretion, the patient's multiple myeloma was stage III-B. A skeletal survey revealed no bony lesions, and magnetic resonance imaging of the axial skeleton revealed marrow abnormalities consistent with myeloma but no osseous lesions. Given the new onset of renal insufficiency and partial Fanconi's syndrome with massive urinary light chain excretion, a renal biopsy was performed to determine the pattern of dysproteinemia-related renal disease.