An 83-year-old woman experienced 4 months of generalized muscle pain. She had also recently undergone an operation for right carpal tunnel syndrome. On exam, she had a bodybuilder-like appearance (Fig. 1) without macroglossia. Lab results showed anemia (hemoglobin level, 7.0 g/dL), hypercalcemia (11.5 mg/dL; corrected with albumin), and hyperimmunoglobulinemia D with other globulin suppression. Serum creatinine level was 0.80 mg/dL, and creatine kinase (CK) was 126 U/L. An IgD-lambda monoclonal component was detected in serum immunofixation electrophoresis, and bone marrow biopsy revealed atypical plasma cells (69.6 %). She was subsequently diagnosed with IgD myeloma. Computed tomography revealed muscle hypertrophy and infiltrated subcutaneous fat (Fig. 2), consistent with amyloidosis.1,2 IgD myeloma accounts for only 1–2 % of all myeloma.3 Clinical manifestations in IgD myeloma can differ from non-IgD myeloma, including a higher incidence of amyloidosis (44 %) than in other myelomas (15 %).4 Differential diagnoses of diffuse skeletal muscle hypertrophy include hypothyroidism and a few neuromuscular disorders such as muscular dystrophies and non-dystrophic myotonic disorders.5 Unlike these diseases, serum CK is often normal in patients with amyloidosis.6 It is important to consider amyloidosis, in particular when serum CK is not elevated, for the patients whose muscles are hypertrophic without exercise.

Fig. 1
figure 1

View of the back showing hypertrophic muscles.

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Fig. 2
figure 2

Contrast-enhanced computed tomographic image showing hypertrophy of the erector spinae muscles (arrow) and soft tissue infiltration in subcutaneous fat (arrowhead).

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