Primary Localized Cutaneous Nodular Amyloidosis of the Thighs
Primary localized cutaneous nodular amyloidosis (PLCNA) is a rare form of cutaneous amyloidosis. We report the case of a 65-year-old woman with multiple asymptomatic discrete nodules and atrophic plaques on the thighs of 4 years’ duration that had increased in number and size. Results of extensive clinical, histologic, and laboratory evaluation showed no evidence of systemic amyloidosis or myeloma. A diagnosis of PLCNA was made. The patient refused treatment due to the asymptomatic nature of the lesions, and follow-up examination 2.5 years later showed minimal progression of the disease.
Practice Points
- The cutaneous lesions of primary localized cutaneous nodular amyloidosis (PLCNA) may present as single or multiple nodules, occasionally with overlying atrophic plaques and some with surface telangiectasia.
- Primary localized cutaneous nodular amyloidosis may represent a localized plasma cell dyscrasia that can be associated with a monoclonal gammopathy or multiple myeloma.
- Although PLCNA often is a benign cutaneous disorder, some patients can develop underlying systemic amyloidosis or even paraproteinemia.
The histopathologic examination of PLCNA is characterized by large deposits of amorphous, sometimes fissured, pale, eosinophilic material in the papillary dermis, reticular dermis, and subcutaneous fat. The overlying epidermis may exhibit flattened rete ridges. Amyloid may occur within vessel walls and adnexal structures, sometimes in a ring surrounding individual fat cells. Clinically, the lesions of PLCNA may be indistinguishable from nodular deposits of amyloid occurring in primary systemic amyloidosis or myeloma-associated amyloidosis. Histopathologically, PLCNA usually has a variable infiltrate of plasma cells and lymphocytes at the periphery or within the amyloid deposits,6 but no single stain is highly sensitive and specific. Congo red–stained deposits showed salmon pink amorphous material or apple green birefringence with polarizing microscopy.8 Amyloid derived from immunoglobulin light chains, including cutaneous nodular amyloid, also stain positive for anti-human λ light chain antibody on immunohistochemistry. Additionally, amyloid can stain positively with methyl violet and crystal violet Gram stains, Picrosirius red, thioflavin T, Dylon, and periodic acid–Schiff stains.
Clinically, some PLCNA lesions can be removed via surgical excision or laser if they are cosmetically disfiguring or symptomatic. Other methods have been attempted to improve the appearance of the lesions, such as intralesional corticosteroids, cryotherapy, and dermabrasion,9 but they usually are not helpful and have a high rate of recurrence. Although PLCNA often is a benign cutaneous disorder and some cases of PLCNA could be reactive diseases rather than neoplastic ones, some patients may develop underlying systemic amyloidosis or even paraproteinemia.10 Northcutt and Vanover11 indicated that systemic amyloidosis may be expected in less than 15% of 47 patients with localized cutaneous amyloidosis during follow-up by reviewing most of the related literature. Some cases may be associated with Sjögren syndrome (SJS), CREST (calcinosis, Raynaud phenomenon, esophageal motility disorders, sclerodactyly, and telangiectasia) syndrome, dermatomyositis, and diabetes mellitus.12-14 Polyclonal immunoglobulin amyloid has been reported only in PLCNA with SJS, which may be due to the fact that a certain population of SJS develops polyclonal B-cell proliferation and hyperglobulinemia.12 Woollons and Black15 estimated the rate of progression of PLCNA to systemic amyloidosis to be only 7%, which is much lower than the rate in the literature by a large clinical follow-up study on PLCNA.16 However, all patients with PLCNA should have a systemic evaluation and should be advised to undergo long-term clinical follow-up to help prevent progression to systemic amyloidosis or plasma cell dyscrasia.
