Gouty tophus of the patella evaluated by PET imaging

Tophaceous Gout of the Lumbar Spine Mimicking Malignancy on FDG PET/CT

A 46-year-old man with over a 10-year history of gout complained of progressive bilateral buttock pain with numbness of legs for 4 months. Serum uric acid level was elevated. Lumbar radiographs showed decreased density of the bilateral L4-L5 facet joints. CT showed lytic lesions of the facet joints with hyperdense periarticular lesions. Enhanced MRI showed marked enhancement of these lesions. FDG PET/CT showed avid FDG uptake of the bony and periarticular lesions with SUVmax of 16.8. A decompressive posterior lumbar laminectomy with periarticular lesion resection was performed. Histopathologic findings of the periarticular lesions were consistent with tophaceous gout.

Solitary subcutaneous gouty nodule mimicking metastatic melanoma on FDG PET/CT

A 68-year-old man with a history of malignant melanoma in the right axilla underwent FDG PET/CT. The images demonstrated a focally increased activity in the subcutaneous tissue anterior to the distal left tibia, suggestive of metastasis. However, a gouty tophus was diagnosed pathologically after biopsy.

Spinal and sacroiliac gouty arthritis: report of a case and review of the literature

In this case report, we describe an "uncommon" case of axial gouty arthropathy in a 69-year-old woman with bilateral sciatica that was thoroughly evaluated with conventional radiography, CT scan, magnetic resonance imaging, bone scintigraphy, and PET-CT. Axial gouty arthropathy should be included in the differential diagnosis of chronic low back pain, mainly when several risk factors for gout are present.

Cutaneous and subcutaneous imaging on FDG-PET: benign and malignant findings

F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) has been shown to be useful in the evaluation of many tumors due to its high sensitivity and specificity. However, false-positive interpretations may occur from benign subcutaneous and cutaneous etiologies. At our institution we have encountered FDG-PET scans which demonstrated a variety of cutaneous and subcutaneous lesions including stomas, hernias, rhinophyma, dose infiltrations, physiologic muscle uptake, and tophaceous gout. Additionally, malignant cutaneous and subcutaneous malignant lesions may also demonstrate substantial F-18 FDG uptake on PET scans, including lymphoma, skin metastases, and melanoma. The purpose of this atlas article is to demonstrate and review key features of various cutaneous and subcutaneous lesions, both benign and malignant, which can result in hypermetabolism on FDG-PET or PET-CT scans.

Musculoskeletal pitfalls in 18F-FDG PET/CT: pictorial review

OBJECTIVE

Thorough evaluation of the musculoskeletal system on PET/CT requires a fund of specialized knowledge and the use of musculoskeletal-oriented viewing techniques. The study of musculoskeletal pitfalls introduces many subspecialty-specific topics and provides instruction in the methods necessary for optimal evaluation of the musculoskeletal system when interpreting PET/CT.

CONCLUSION

This article reviews musculoskeletal pitfalls in PET/CT. On completion, reviewers should have an improved ability to evaluate the musculoskeletal system on PET/CT.

Pseudotumor of gout in the patella of a kidney transplant recipient

BACKGROUND

A 33-year-old renal transplant recipient presented with painless swelling of the right knee. Physical examination revealed an impressive knee joint effusion with no signs of inflammation. The patient did not remember a recent trauma, but he mentioned a strain 3 years earlier; radiographic findings had been normal at that time. The patient had suffered from end-stage renal disease due to chronic glomerulonephritis and had previously undergone two transplantations. At presentation, his kidney function was stable under treatment with ciclosporin, azathioprine and steroids.

INVESTIGATIONS

Conventional radiography revealed a tumor at the superolateral pole of the right patella. Extensive soft tissue invasion and bone destruction was seen on MRI. A knee arthroscopy with biopsy, performed to aid diagnosis, showed extensive chondrocalcinosis macroscopically; histologically, gouty tophi were found.

DIAGNOSIS

Pseudotumor of gout in the patella.

MANAGEMENT

Uric-acid-lowering therapy with benzbromarone was started immediately after diagnosis. A local arthroscopic debridement of the right knee joint was performed 4 months later, and the patient remained asymptomatic for the next 3 years.

The advanced imaging of gouty tophi

Gout is a metabolic disorder in which there is hyperuricemia caused by an increase in production or a decrease in excretion of uric acid. Long-lasting hyperuricemia causes the deposition of monosodium urate crystals in the joints and soft tissues, triggering gouty arthritis and, if not properly treated, the formation of gouty tophi. The diagnosis of gout is usually based on clinical presentation and laboratory examinations, long before any abnormality can be demonstrated with imaging. Radiography is the primary imaging modality used in the initial evaluation of gouty arthritis. Ultrasonography, CT, MRI, and nuclear medicine are seldom necessary. Occasionally a tophus has an unusual presentation and simulates neoplasm or infection prompting the utilization of cross-sectional imaging for further evaluation and surgical planning. Cross-sectional imaging is also used in areas that are difficult to visualize on radiographs such as spine, sacroiliac joints, and soft tissues.

Calcific Tendinosis: A Potential Mimicker of Malignancy on PET

We report a case of a 53 year old female with breast cancer and elevated glucose activity at the left greater trochanter on PET imaging. Further imaging with CT and MRI showed that this focus of increased FDG activity on PET was calcific tendinosis of the gluteus medius tendon, which mimicked metastatic disease in this patient.

Tophaceous gout in the bipartite patella with intra-osseous and intra-articular lesions: a case report

We report a case of a 34-year-old man who had an acute gouty attack with tophi around the accessory bone of the bipartite patella with intra-osseous lesions. As the symptoms did not respond to conservative treatments, the patient was treated surgically. Arthroscopy revealed urate crystals surrounded by inflammatory synovitis on the surface of the bipartite patella. Arthrotomy exposed the abundant crystals around the accessory bone and in the intra-osseous lesion. These findings made us speculate that some pre-existing inflammatory conditions around the accessory bone induced deposition of urate crystals, and the destruction of the barrier between the deposits and the joint led to an acute arthritis. Curettage of the tophi resulted in immediate improvement of knee function. There had been no recurrence of symptoms at the 2-year follow-up.