Anti-NXP2-Positive Paraneoplastic Dermatomyositis With Histopathologic Changes Confined to the Acrosyringia.

Background: Paraneoplastic syndromes consist of a group of disorders that are not related to the extension of the primary tumor or its metastases and that might be the first manifestation of a hidden neoplasm. It is a well-known association between dermatomyositis (DM) and cancer, especially gynecological tumors in women and lung cancer in men.
Methods: We describe the case of a 67-year-old male who developed muscular weakness and pruritic skin lesions. Skin biopsies were performed and histologic findings were consistent with DM.
Results: Skin biopsy showed interface dermatitis with vacuolar degeneration of the basal layer, dermal mucin deposits, and necrotic keratinocytes in the acrosyringia, a finding that has been previously reported in lupus erythematous but not in DM. Autoimmunity tests showed positivity for antinuclear antibodies and anti-NXP2, a recently described antibody associated with juvenile DM and, more rarely, with paraneoplastic DM.
Conclusion: We present the first case in the literature with histopathologic changes of DM affecting the acrosyringia. Besides, our patient autoimmunity results support the utility of the new myositis-specific autoantibodies and its relation with a clinical phenotype.