Association of knee atypical lesions with foot ulcers and a peak of kappa IgM monoclonal immunoglobulin

the Department of Dermatology, Brest University Hospital, est, France; Department of Hematology, Brest University ospital, Brest, France; Department of Pathology, Henriondor Hospital, AP-HP, Cr eteil, France; Department of thology, Brest University Hospital, Brest, France; and epartment of Neurology, Brest University Hospital, Brest, ance. ing sources: None. pproval status: Not applicable. nt consent: Consent for the publication of all patient otographs and medical information was provided by the thors at the time of article submission to the journal stating that the patient gave consent for his photographs and medical information to be published in print and online and with the understanding that this information may be publicly available. Correspondence to: Laurent Misery, MD, PhD, Departement of Dermatology, University Hospital of Brest, 2 Ave Marechal Foch, 29200, Brest, France. E-mail: laurent.misery@chu-brest.fr. JAAD Case Reports 2023;33:17-9. 2352-5126 a 2023 by the American Academy of Dermatology, Inc. Published by Elsevier, Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1016/j.jdcr.2022.12.016


PRESENTATION
An 84-year-old man presented with small erythematous, necrotic papules on the knees (Fig 1) and the dorsal side of hands, associated with 2 plantar ulcers and paraesthesias. Pancytopenia and a peak of kappa IgM monoclonal immunoglobulin (28.3 g/L), with free kappa light chains, were noted. A Bence-Jones kappa-like proteinuria was present. Bone marrow aspirate analysis revealed a B-cell infiltration (45% of CD191 cells) with intermediate kappa immunoglubulins (92%). Immunohistochemical analysis of knee lesion revealed large deposits of amyloid-like substance that was immunoreactive for anti-kappa antibody (Fig 2). Computed tomography scan showed osteoarthritis of the left fifth metatarsophalangeal joint. Electroneuromyography revealed axonal sensorimotor polyneuropathy.

Answers:
A. Purpura secondary to thrombocytopenia e Incorrect. These lesions are rather necrotic and no other purpuric lesions were observed. Thrombocytopenia was not severe (platelet count: 78 3 10 9 /L).
B. Wounds secondary to trauma e Incorrect. No trauma was reported.
C. Skin infection e Incorrect. There was no erythematous border or pus.

D.
Cutaneous amyloidosis e Incorrect. No applegreen birefringence with Congo red staining on polarized light microscopy was observed. Cutaneous symptoms of amyloidosis are a peculiar form of purpura in a periorbital distribution (''raccoon eyes''), waxy thickening of the skin, easy bruising, and subcutaneous nodules or plaques, which are very different lesions from those of this patient. Hence, the diagnosis of cutaneous amyloidosis can be excluded clinically.
E. Cutaneous macroglobulinosis (CM) e Correct. CM is characterized by the deposition of eosinophilic, immunoglobulin-derived material in the dermis. It typically presents as pink or skincolored papules favoring the extensor surfaces of the extremities. 1 It is rare and only some small case series have been reported.

Answers:
A. An equivalent of amyloidosis in Waldenstr€ om's disease e Incorrect. Amyloidosis refers to the deposition of fibrils within extracellular tissues of light chains in a ß-pleated sheet configuration. 1 B. An indirect consequence of the deposition of immunoglobulins e Incorrect. IgM is a polymer characterized by multiple immunoglobulins linked together by strong covalent bonds, giving rise to pentamers. The combination of increased vascular permeability, high serum concentration, and presence of specific antigens in the skin may result in its deposition within the dermis. 1 Hence CM is a direct consequence of the deposition of immunoglobulins.

C.
A specific manifestation of Waldenstr€ om's disease e Correct. Non-specific findings are attributed to hyperviscosity or cryoglobulinemia, whereas specific manifestations are related to neoplastic B-cell infiltrates and monoclonal IgM deposition in the skin. 4,5 This case is notable because Waldenstr€ om's disease was revealed by both non-specific (neuropathic ulcers) and specific (CM) skin manifestations. The occurrence of the neuropathy is thought to be related to the accumulation of IgM in myelin sheaths. 3 D. A frequent condition e Incorrect. It is very rare and there are only some case reports in the literature. 1,4,5 E. A predictive factor in all cases e Incorrect. Patients can develop CM before, concurrent with, or e as in our reported case e after diagnosis of the underlying lymphoplasmacytic lymphoma. Hence, CM can predict a latent plasma cell dyscrasia before any other clinical or pathologic evidence 5 but not in all cases.
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Conflicts of interest
None disclosed.