Formation of immunoglobulin light chain amyloid oligomers in primary cutaneous nodular amyloidosis

Background Primary cutaneous nodular amyloidosis (PCNA) is thought to be a plasma cell dyscrasia. The amyloid deposits are found in the dermis and subcutis, and they contain clonal immunoglobulin light chains, produced by a local proliferation of plasma cells. New insights into amyloid diseases have revealed that the pathology is due more to the presence of small, misfolded protein species termed oligomers than to the deposition of fibrillar material. Objectives To demonstrate the presence of amyloid oligomers in PCNA and to provide evidence that cutaneous amyloid diseases share a common pathogenic pathway similar to other amyloid diseases. Methods Immunohistochemical staining with conformation‐specific and sequence‐specific antibodies was used to localize different amyloid species of light chain immunoglobulins in a case of PCNA. Additionally, in vitro characterization of immunoglobulin oligomers and fibrils was performed to determine, through toxicity studies in a human keratinocyte cell line, which amyloidogenic form of the immunoglobulin is toxic in PCNA. Results Amyloid oligomers were identified in PCNA. Oligomers were mainly formed by lambda light chain immunoglobulins, and kappa light chain oligomers were detected in lesser amounts. Amyloid species were detected intra‐ and extracellularly. In addition, amyloid oligomers and fibrils, derived from unknown protein sources, were detected. This finding suggests that immunoglobulin amyloids can act as seeds capable of inducing the aggregation of heterogeneous proteins in the skin. Furthermore, cytotoxicity studies demonstrated that immunoglobulin oligomers, but not monomers or fibrils, are toxic to human keratinocytes. Conclusions These data indicate that PCNA has common pathways with other amyloid diseases with respect to protein misfolding and pathogenesis. Immunoglobulin oligomers may prove to be targets for the treatment of PCNA.     

Partial amino acid sequence of an amyloid fibril protein from nodular primary cutaneous amyloidosis showing homology to lambda immunoglobulin light chain of variable subgroup III (a lambda III)

An amyloid fibril protein (MA) was purified as a 17,000-dalton protein from a case of nodular primary cutaneous amyloidosis, and its partial amino acid sequence (22 residues from N-terminal) was determined. A sequence closely homologous to that of the lambda III subgroup of the immunoglobulin light chain was detected. This is the third case of nodular primary cutaneous amyloidosis which has been studied at the level of sequence analysis of purified amyloid fibril proteins, and the first case of nodular primary cutaneous amyloidosis in which a lambda III amyloid protein has been shown to be present by sequence analysis.     

Cutaneous B cell lymphocytic lymphoma associated with paraproteinaemia

A 62-year-old lady with a well-differentiated B cell lymphoma demonstrates the typical clinical features of this unusual condition. In addition she had an associated paraproteinaemia. Histopathologically this condition may be difficult to differentiate from pseudolymphoma with conventional stains. Using an immunoperoxidase technique we were able to demonstrate the production of a monoclonal immunoglobulin by the infiltrating lymphocytes thus confirming the malignant nature of the lymphoma.     

Two cases of nodular cutaneous amyloid with positive organ-specific antibodies, treated by shave excision

Two cases with nodular cutaneous amyloid on the face were treated by shave excision with excellent cosmetic results. Both showed positive thyroid microsomal and gastric parietal cell autoantibodies but no evidence of systemic amyloidosis. The presence of autoantibodies raises the possibility that primary cutaneous nodular amyloid may be associated with autoimmune disorders. Primary nodular cutaneous amyloid is an uncommon disorder. A recent view of the literature has identified 47 reported cases to date.¹ The nodules are usually confined to the skin so the prognosis tends to be good, although systemic amyloidosis² and associated monoclonal gammopathy³ have been recorded. Of 12 cases in the Japanese literature, four have been associated with Sjogren's syndrome,⁴ which itself is associated with the presence of specific and non-organ specific autoantibodies.     

Primary localized cutaneous nodular amyloidosis: case report and biochemical analysis of amyloid.

We report a patient with scalp lesions of primary localized cutaneous nodular amyloidosis. The extensive examination revealed no systemic involvement. Analysis of glycosaminoglycans (GAGs) in amyloid deposits showed a twofold increase as compared with normal skin, which was due to the increase in dermatan sulfate. Local disorders of GAG metabolism may be related to the amyloid fibril formation. Amyloid fibrils were purified and identified electron-microscopically, which consisted of two major 12,000- and 13,000-dalton and minor 29,000- and 48,000-dalton peptides. Western blotting analysis showed a minor 29,000-dalton peptide reactive with antibodies against both kappa and lambda light chains of immunoglobulin. There is a possibility that some components of amyloid in some cases of primary localized cutaneous nodular amyloidosis may consist of both kappa and lambda immunoglobulin light chains.     

Salivary gland hyalinizing clear‐cell carcinoma with cutaneous metastasis: A rare and deceptive tumor

Clear‐cell carcinoma (CCC) is an uncommon malignant tumor of minor salivary glands. It characteristically has a low‐grade morphology and a favorable outcome by most reports. An EWSR1‐ATF1 fusion can be detected in the majority of cases. We present a rare case of CCC, which had an aggressive course with the development of cutaneous metastases. Practicing dermatopathologists should be aware of this tumor given its low‐grade appearance and histopathologic resemblance to other primary cutaneous adnexal and metastatic neoplasms.     

Primary cutaneous nodular amyloidosis associated with psoriasis

Primary cutaneous nodular amyloidosis (PCNA) presents as solitary or multiple firm, waxy nodules with a predilection for acral areas. Histologically, PCNA can be identical to myeloma‐associated systemic amyloidosis with monoclonal immunoglobulin light chain deposits. We describe a patient in whom PCNA developed in a scar in an area affected by chronic plaque psoriasis. PCNA has previously been associated with other autoimmune diseases, but to our knowledge, this is the first association with psoriasis. Interestingly, T helper (Th)17 cells, which are crucial in psoriasis pathogenesis, have recently been implicated in promotion of myeloma and plasma cell dyscrasias. The association of psoriasis and plasma‐cell light chain production in the skin, as in this case, suggests a possible role for Th17 cells in PCNA formation. The dermatopathological literature of this rare but important disease is discussed.     

Primary localized cutaneous nodular amyloidosis successfully treated with cyclophosphamide

Primary localized cutaneous nodular amyloidosis (PLCNA) is a rare subtype of localized cutaneous amyloidosis and can be associated with various connective tissue disorders. It can be difficult to treat and past therapies include surgical excision, dermabrasion, electrodessication and curettage, cryotherapy and laser therapy. We present a case of a middle‐aged woman with PLCNA associated with CREST (calcinosis, Raynaud phenomenon, oesophageal motility disorders, sclerodactyly and telangiectasia) syndrome and Sjögren's syndrome responding to cyclophosphamide with no new amyloid deposits and resolution of skin ulceration after many years of resistance to drug therapy. It is important to monitor these patients for progression into systemic amyloidosis.     

Primary cutaneous marginal zone lymphoma with subclinical cutaneous involvement and biclonality

Primary cutaneous extranodal marginal zone lymphoma (MZL) of mucosa-associated lymphoid tissue (MALT) represents a monoclonal B-cell neoplasm that typically presents with papules, plaques or nodules. We describe a patient with a primary cutaneous MALT lymphoma with unusual clinical features and an unusual immunophenotype. Conventional microscopy together with immunohistochemistry and in-situ hybridization showed the presence of lymphoma in normal-appearing and minimally erythematous skin as well as in clinically involved skin. Furthermore, at least two distinct clones were shown, one of which had κ-light chain restriction, and the other of which had λ-light chain restriction. This case represents a newly described clinical appearance of primary cutaneous MZL and shows that some patients may have more than one neoplastic clone.     

Treatment of cutaneous lymphoma with etretinate

Twelve patients with various types of lymphoma were treated with etretinate. The diagnosis included parapsoriasis en plaque, epidermotropic lymphoma (diffuse chronic erythroderma with atypical mononuclear cells, Sézary syndrome or MF tumours) and non-epidermotropic lymphoma. The patients received etretinate in a dose of 0.8 to 1.0 mg/kg/day for 2 to 14 months. No additional therapy was given. Patients with epidermotropic lymphomas stage I and II had a favourable clinical and histological response whereas those with deeply infiltrating tumours remained unresponsive. Patients with parapsoriasis en plaque and poikiloderma showed little response. Of the four patients who discontinued the treatment, three had recurrences after 3 to 4 months but one remained clear. The results obtained with etretinate may equal those obtained with more aggressive treatments.