Background Acute
tubulointerstitial nephritis (ATIN) is a very rare paraneoplastic manifestation in
patients with
multiple myeloma (MM). It is an uncommon pattern of renal
disease in such
patients. Case presentation We
report a case of an 82-year-old
male who was admitted with
acute kidney injury. Renal
biopsy showed typical findings of
light chain-associated ATIN with scattered inflammatory
cells in the interstitium and associated active tubulitis. No other common manifestations of MM were present at the
time of presentation, including
hypercalcemia,
hyperuricemia,
proteinuria,
bone pain or lytic
bone lesions. Subsequent
immunoassays revealed significant
serum lambda
light chain burden and Bence Jones
protein in
urine.
Immunofluorescence demonstrated linear tubular
basement membranes with positive
staining for lambda
light chain (3+).
Electron microscopy (EM) further showed interstitial
edema and
inflammation. All the aforementioned findings are consistent with ATIN and supported the
diagnosis of MM. Conclusions In conclusion,
light chain-associated ATIN should be considered in the
differential diagnosis of acute
interstitial nephritis. Henceforth,
serum free
light chains as well as
serum and
urine protein electrophoresis should be included in the workup of such
patients.