Dual-Energy Computed Tomography (DECT) Resolves the Diagnostic Dilemma in an Atypically Presenting Case of Gout

Gout is a common inflammatory arthropathy that presents as acute monoarthritis, most commonly of the first metatarsophalangeal (MTP) joint. Chronic polyarticular involvement may lead to confusion with other inflammatory arthropathies, including rheumatoid arthritis (RA). A thorough history, physical examination, synovial fluid analysis, and imaging are keys to establishing a correct diagnosis. Although a synovial fluid analysis remains the gold standard, the affected joints may be difficult to access by arthrocentesis. In cases where a large monosodium urate (MSU) crystal deposition is in the soft tissues - the ligaments, bursae, and tendons, it becomes a clinical impossibility. In such cases, dual-energy computed tomography (DECT) can assist in differentiating gout from other inflammatory arthropathies, including RA. Additionally, DECT can perform quantitative analysis of tophaceous deposits and, therefore, assess response to treatment.

A Rare Case of Destruction of the First Metatarsophalangeal Joint in a Patient With Gout

Gout is a crystal deposition disorder caused due to the deposition of monosodium urate crystals in joints and other tissues secondary to hyperuricemia. Podagra is the term for gout of the first metatarsophalangeal joint. In our case report, a 30-year-old male patient came to our OPD with complaints of swelling over the first metatarsophalangeal joint for one year, which was insidious in onset, localized, and had a sudden increase in size over the past three months. The patient also complained of an inability to properly wear his shoe. A plain radiograph was done, which was suggestive of an expansile lesion with the destruction of the first metatarsophalangeal joint and the erosion of the joint surface extending to the head of the first metatarsal and the proximal phalanx of the great toe. Lab investigations revealed a serum uric acid level of 10.2 mg/dl and an acid phosphatase level of 8.92 U/L. Excision of the lesion was done and a frozen section biopsy was sent intra-operatively which confirmed the presence of monosodium urate crystals. A fibular strut graft was taken to fill the defect using a square nail passing through the first metatarsophalangeal joint and a Kirschner wire was added to the interphalangeal joint to maintain the stability of the reduction. The foot was immobilized for six weeks following which the Kirschner wire was removed and range-of-motion exercises started. There was no residual deformity, and the patient responded well to the treatment.

Dual-energy CT assessment of rapid monosodium urate depletion and bone erosion remodelling during pegloticase plus methotrexate co-therapy

OBJECTIVES

Pegloticase rapidly lowers serum urate in uncontrolled/refractory gout patients, with ≥1 tophus resolution in 70% of pegloticase responders and 28% of non-responders. Dual-energy computed tomography (DECT) non-invasively detects MSU deposition, including subclinical deposition, quantifies MSU volumes and depicts bone erosions. This report presents DECT findings in MIRROR open-label trial participants receiving pegloticase+MTX co-therapy.

METHODS

Serial DECT scans were obtained during pegloticase (8 mg biweekly infusions)+oral MTX (15 mg/week) co-therapy. Bilateral hand/wrist, elbow, foot/ankle and knee images were analysed with default post-processing settings. MSU volumes were quantified and bone erosions were identified and evaluated for remodelling (decreased size, sclerosis, new bone formation). DECT and physical examination findings were compared.

RESULTS

2 patients underwent serial DECT. Patient 1 (44-year-old male) completed 52 weeks of pegloticase+MTX co-therapy (26 infusions). Baseline examination detected 4 tophus-affected joints while DECT identified 73 MSU-affected joints (total MSU volume: 128.76 cm3). At end-of-treatment, there were no clinically-affected joints and 4 joints with DECT-detected MSU deposition. MSU volume decreased by 99% and bone erosion remodelling was evident. Patient 2 (51-year-old male) had 10 weeks of therapy (5 infusions), discontinuing because of urate-lowering response loss. Baseline examination detected 7 tophus-affected joints while DECT identified 55 MSU-affected joints (total MSU volume: 59.20 cm3). At end-of-treatment, there were 5 clinically affected joints and 42 joints with DECT-detected MSU deposition. MSU volume decreased by 58% and bone erosion remodelling was evident.

CONCLUSION

DECT detected subclinical MSU deposition and quantified changes over time. Rapid tophus resolution and bone erosion remodelling occurred during pegloticase+MTX co-therapy.

TRIAL REGISTRATION

ClinicalTrials.gov, https://clinicaltrials.gov, NCT03635957.

Role of Dual-Energy Computed Tomography in the Identification of Monosodium Urate Deposition in Gout Patients: A Comprehensive Analysis of 828 Joints According to Structural Joint Damage

Background

Dual-energy computed tomography (DECT) has become a promising, non-invasive procedure for the visualization, characterization, and quantification of monosodium urate (MSU) crystals, which aids clinicians in the diagnosis of gout. In this study, we aimed to examine the diagnostic accuracy of DECT in the evaluation of gout.

Methodology

This cross-sectional retrospective study included patients who were clinically diagnosed with gout and underwent a DECT scan.

Results

A majority (80.4%) of the MSU deposits were found in the ankle joints. The presence of MSU deposits on DECT scan was highly correlated with bone erosion in the upper limb (odds ratio [OR] = 132; 95% confidence interval [CI] = 17.3-1004.3), bone sclerosis in the lower limb (OR = 36.4; 95% CI = 15.4-86.1), bone erosion in metacarpophalangeal joints (OR = 160; 95% CI = 42.7-600.2), and bone sclerosis in metatarsophalangeal joints (OR = 35.6; 95% CI = 15.5-81.9). Using linear regression analysis on patient-level data, correlations were found between DECT MSU crystal deposition and damage on all categories of structural joint damage showing significant association with erosion (r = 0.91, p < 0.001) and space narrowing (r = 0.75, p < 0.001) but not with joints having periarticular calcification (r = 0.52, p < 0.041).

Conclusions

Our study established DECT as a valid method for detecting MSU deposits and their association with structural joint deterioration in a Vietnamese population.