Fluorodeoxyglucose PET in Relapsing Polychondritis

Abstract

We report on a case of fever of unknown origin in which 18F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) was instrumental in depicting cartilage inflammation, which eventually led to a histologically confirmed diagnosis of relapsing polychondritis. Relapsing polychondritis is a rare inflammatory disease that may affect cartilage throughout the body, but the diagnosis may be challenging in the absence of typical auricular or nasal involvement, as in the patient described here.1 A 67-year-old man presented with a 1.5-year history of persistent cough with clear secretions, progressive shortness of breath, sore throat, bloated stomach, low-grade fever, malaise, and weight loss. Physical examination revealed tenderness on all sternocostal junctions and in the laryngeal region. Vesicular breath sounds were decreased. The erythrocyte sedimentation rate was 130 mm per hour, and the C-reactive protein level was 20.0 mg per deciliter (normal level, <0.5). The white-cell count was 15,000 per cubic millimeter, with 86% neutrophils. The lactate dehydrogenase level was 516 U per liter (normal range, 240 to 480). All cultures and serologic tests were negative. The antinuclear factor level was normal, and the level of c-antineutrophilic cytoplasmic antibodies was slightly increased. The patient's condition improved with the administration of corticosteroids for the treatment of asthma, but he did not have a complete recovery. As part of a diagnostic workup, the patient underwent whole-body PET with FDG (FDG-PET). The imaging study revealed marked tracer uptake in all rib cartilages, as well as in the larynx, trachea, and major bronchi (Figure 1AFIGURE 1 Positron-Emission Tomographic (PET) Studies with 18F-fluorodeoxyglucose in a Patient with Relapsing Polychondritis. ). Surgical biopsy of the 12th rib cartilage, shown to be involved on PET, provided histologic confirmation of the diagnosis. Treatment with methylprednisolone and dapsone induced disease remission. After 5 months, while receiving a daily dose of 8 mg of methylprednisolone, the patient had a relapse. The dose of methylprednisolone was increased to 32 mg, and cyclophosphamide (at a daily dose of 100 mg) was administered. At that time, severe retro-obstructive bilateral pneumonia developed. Antibiotics were temporarily added to the regimen, and endobronchial stents were inserted. Nine months after his condition had been diagnosed, the patient again had a clinical and biochemical remission, and cartilaginous tracer accumulation had largely disappeared on a new PET study (Figure 1B). Evidence supporting the pivotal role of FDG-PET in the diagnosis of fever of unknown origin is increasing steadily.2,3 The case we describe illustrates the role of FDG-PET in the diagnosis of relapsing polychondritis, especially in patients who do not have typical manifestations. By localizing sites of active inflammation, FDG-PET may guide the selection of a biopsy site.2 Like other reported cases, this case shows the correlation between the findings on FDG-PET and disease activity, as assessed by clinical and laboratory measures.4