Purpuric Bullous Skin Eruption as an Early Sign of Inconspicuous Multiple Myeloma: A Case of Amyloidosis

Purpuric bullous amyloidosis is rare skin manifestation of primary systemic amyloidosis. We present a case of 59-year-old female with multiple myeloma who only presented with symptoms of amyloidosis. The patient presented with ill-defined, yellowish, flaccid bullous patches with multiple purpuric macules in intertriginous areas for 5 years. Necrobiotic xanthogranulomas and xanthoma disseminatimi were considered based on their appearance, but histopathological examination ruled them out. The examination revealed loose dermal collagen bundles and elastic fiber fragmentation. Amyloidosis could not be definitively excluded due to presence of amorphous eosinophilic material around the vessels. Electron microscopy confirmed presence of amyloid deposits by demonstrating non-branching, randomly ordered fibrils within 10 nm in diameter. Although systemic symptoms were insufficient to raise suspicion for multiple myeloma, bone marrow biopsy and whole skeletal computed tomography scan revealed early-stage multiple myeloma. This case highlights how uncovering amyloidosis can be the first clue leading to diagnosing inconspicuous multiple myeloma.