[Pseudo-hypertrophic pelvi-crural amyloid myopathy in lambda light-chain myeloma. Clinical, morphological and...

The case of 65 year old woman with progressive enlargement and "wooden" induration of the pelvic girdle and thigh muscles due to an amyloid infiltration is reported. Muscle changes appeared two years after a diagnosis of myeloma with free lambda light chains. The patient complained of muscle pain, lassitude and weakness. Macroglossia was present. Skeletal muscle (vastus lateralis) contained large amounts of amyloid substance and showed type 2B atrophy. There was no fiber type grouping. Some amyloid deposits abutted on the muscle fiber, destroyed the basal lamina and sarcolemma, but never infiltrated it. Besides the amyloid phagocytosis by macrophages, a relationship between amyloid filaments and fibroblasts was present. Another non-congophilic substance was revealed using the Avidin-Biotin peroxidase complex to localize lambda light chains by light microscopy and corresponded to a granular substance in electron microscopy. Clinicopathological results are discussed with a review of thirteen similar cases previously reported.