Crystalline κ light-chain proximal tubulopathy and Auer rod-like inclusions presenting as Fanconi syndrome: A case report.
Yu Wang, Li Zhang, Chang-Jiu Liang et al.
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Case in brief
A 53-year-old man presented with Fanconi syndrome, with hypokalemia, hypophosphatemia, mild metabolic acidosis, and renal glucosuria. Kidney biopsy showed crystalline light-chain proximal tubulopathy, with κ-restricted light chains in proximal tubular epithelial cells. Bone marrow examination identified multiple myeloma; the plasma cells contained Auer rod-like intracytoplasmic inclusions. The report links the renal crystals and plasma-cell inclusions to monoclonal κ light chains, while noting that their shared physicochemical basis remains a suggestion rather than an established mechanism.
What made this case unusual
The coexistence of crystalline κ-restricted proximal tubulopathy and Auer rod-like inclusions in myeloma plasma cells is exceedingly rare and poorly characterized.
Diagnostic / clinical pearl
In unexplained Fanconi syndrome, kidney biopsy can identify crystalline light-chain proximal tubulopathy and help reveal an underlying monoclonal plasma-cell disorder.