Unique morphology of intratubular light chain casts in multiple myeloma: the amyloid cast nephropathy

Cast nephropathy is the most frequent pattern of renal involvement in multiple myeloma characterized by presence of tubular casts with characteristic morphology that are composed of monotypic (either kappa or lambda) light chains as seen by immunofluorescence microscopy. Rarely these casts may show evidence of amyloidogenesis and assume a unique morphology, which needs to be appreciated for arriving at accurate diagnosis. We present the case of an elderly male presenting with features of acute kidney injury and detected with extensive inspissation of intratubular casts with lambda light chain restriction and a unique morphology with spiculated congophilic periphery. Further investigations confirmed the presence of systemic myeloma. Presence of intratubular amyloid casts is a rare occurrence which needs to be recognized by the pathologist and forms a vital element in timely diagnosis of the systemic disease which often presents with renal involvement.