Primary Localized Cutaneous Nodular Amyloidosis in a Patient with Sjögren's Syndrome: A Review of the Literature

We report a 53‐year‐old Japanese woman with multiple, red, and elastic soft nodules on the left waist, left thigh, and right lower leg. She had had polyclonal hyperglobulinemia for one year, rheumatoid arthritis for 13 years, and Sjögren's syndrome (SjS) for 18 years. Histochemical examination of the nodule on the left thigh revealed a deposition of amyloid by Congo red staining. It was also positively stained with both anti‐κ and ‐λ light chain antibodies. Moreover, the cytoplasm of the infiltrating plasma cells also positively reacted to both antibodies. The major amyloid proteins of primary localized cutaneous nodular amyloidosis (PLCNA) generally consist of monoclonal immunoglobulin light chains. A review of literature demonstrates 13 cases of PLCNA with SjS, in which immunoglobulin light chains were demonstrated in the amyloid in 5 cases. Amyloid in the 3 cases was composed of a single class immunoglobulin light chain and that in the 2 cases was composed of both κ and λ light chains. Polyclonal immunoglobulin amyloid has been reported only in PLCNA with SjS, which may be related to the fact that a certain population of SjS develops polyclonal B cell proliferation and hyperglobulinemia.