Multimodality Molecular Imaging in Arthropathy Associated with Multiple Myeloma

Abstract

We report a patient with multiple myeloma (MM) and polyarthritis of large joints. During the staging of the disease, bone marrow diffusely involved by MM was clearly demonstrated by 99mTc-2-methoxy-isobutyl-isonitrile (MIBI) single-photon emission computed tomography/computed tomography (SPECT/CT) but not by 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/CT images. On the other hand, a very intense uptake of 18F-FDG was detected in periarticular tissues of multiple joints, with nonabnormal 99mTc-MIBI accumulation. Rheumatology tests were negative. A subsequent bone scintigraphy demonstrated radiolabeled bisphosphonate accumulation in periarticular tissues, suggesting amyloid arthropathy.

A female patient, 46-year-old, presented nausea, vomiting, lower limb pain, weakness, and weight loss. Laboratory tests revealed renal failure, anemia, hypercalcemia, and monoclonal peak. Multiple lytic lesions in several ribs and vertebral bodies were identified on chest computed tomography (CT). Myelogram found 44% of clonal plasma cells, consistent with multiple myeloma (MM). The patient also exhibited polyarthritis of large joints, especially in the shoulders and hips. Rheumatology tests were negative. The patient was referred to the nuclear medicine unit for staging.

Marked 99mTc-2-methoxy-isobutyl-isonitrile (MIBI) uptake throughout the skeleton, consistent with diffuse bone marrow (BM) involvement by MM, was evidenced by planar images (arrows on posterior view in [Figure 1a] and single-photon emission computed tomography (SPECT)/CT (arrows on axial plane in Figure 1b). 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT did not detect BM disease [Figure 1c]. This divergence was previously described between the two methods, which were reported as complementary.[1,2,3,4,5] In fact, MIBI is more sensitive than FDG to identify diffuse BM involvement by MM.[1,2,3,4,5]

Figure 1.

46-year-old female patient diagnosed with multiple myeloma. Posterior planar view (a) and SPECT/CT axial slice (b) of 99mTc-MIBI images showed tracer uptake throughout the skeleton, consistent with diffuse bone marrow involvement (arrows). Maximum intensity projection (c) and axial slice of FDG-PET/CT images (d) detected multiple hypermetabolic areas symmetrically involving large joints, especially the pelvic girdle, suggestive of active arthropathy (arrows). Posterior planar view (e) and SPECT/CT axial slice (f) of 99mTc-MDP images showed high periarticular and articular MDP uptake in the same joints with FDG uptake, more intense in the pelvic girdle, suggesting extraosseous periarticular amyloid deposits (arrows)

On the other hand, FDG PET/CT revealed multiple hypermetabolic areas symmetrically involving large joints, especially the pelvic girdle, suggestive of active arthropathy (arrows in [Figure 1d]). MIBI images, which are not sensitive for inflammatory processes, presented normal tracer uptake in these areas [Figure 1a and b]. Periarticular FDG uptake in arthropathy associated with MM has been previously reported[6] and related to light-chain amyloid arthropathy. FDG uptake in rheumatoid arthritis and other rheumatic diseases has also been reported.[7,8] Biopsy of periarticular lesions was indicated for the confirmation of amyloid deposition, which could not be performed owing to the severity of the clinical condition of the patient.

Planar and SPECT/CT 99mTc-methylene diphosphonate (MDP) images were then carried out. These images showed high periarticular and articular MDP uptake in the same joints with FDG uptake, including periarticular soft tissues, more intense in the pelvic girdle (arrows Figure 1e), suggesting extraosseous periarticular amyloid deposits clearly demonstrated by SPECT/CT images (arrows in Figure 1f). There was no CT evidence of calcification in these areas (Figure 1f).

Bone scintigraphy has long been reported to have no place in the routine staging of MM because of its very low sensitivity for bone and extraosseous lesions.[9] However, MDP and other bisphosphonates have been reported to accumulate in MM-associated light-chain amyloidosis, affecting different organs and tissues, with relatively high specificity,[10,11,12] including periarticular tissues.[10] On the other hand, MDP is not expected to accumulate in the periarticular tissue in rheumatoid arthritis or osteoarthritis.[13]

Molecular imaging can access several aspects of disease activity in MM-associated arthropathy, including neoplastic activity, inflammation, and amyloid deposition.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.