FDG PET-CT as a powerful tool for diagnosing and monitoring treatment outcomes of relapsing polychondritis

Relapsing polychondritis with isolated tracheobronchial involvement complicated with Sjogren's syndrome: A case report

BACKGROUND

Relapsing polychondritis (RP) is a rare, long-term, and potentially life-threatening disease characterised by recurrent paroxysmal inflammation that can involve and destroy the cartilage of the external ear, nose, larynx, and trachea.

CASE SUMMARY

We here report a case of RP involving solely the tracheobronchial cartilage ring (and not the auricular. nasal or articular cartilage) complicated by Sjögren's syndrome in a 47-year-old female whose delayed diagnosis caused a sharp decline in pulmonary function. After corticosteroid treatment, her pulmonary function improved.

CONCLUSION

In such cases, our experience suggested that 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and fiberoptic bronchoscopy should be used to diagnose airway chondritis as relapsing polychondritis in the early phase of disease.

Giant cell arteritis manifested by chronic dry cough

A 77-year-old man visited the hospital with a chronic cough persisting for 2.5 months accompanied with night sweats, weight loss (3.5 kg) and elevated C-reactive protein level. Chest CT of the lung field was normal, but aortic wall thickening accompanied by a contrast effect was noted. Positron emission tomography-CT (PET-CT) showed that the aorta and subclavian artery were inflamed, suggesting large-vessel vasculitis. Ultrasonography showed thickening of the superficial temporal artery wall (macaroni sign). Biopsy revealed lymphocytic infiltration in the tunica media and foreign-body giant cell reaction with the elastic lamina, resulting in a diagnosis of giant cell arteritis (GCA). The cough was considered a symptom of GCA as it resolved following prednisolone administration. Cough may rarely be an initial GCA symptom. However, for chronic cough accompanied with elevated inflammatory findings but with a normal lung field, imaging studies such as PET-CT are useful for the differential diagnosis.

Is 18F-FDG PET/CT useful for diagnosing relapsing polychondritis with airway involvement and monitoring response to steroid-based therapy?

Background

¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is a promising tool for diagnosing relapsing polychondritis (RP). However, its usefulness in assessing RP with airway involvement is unknown.

Objective

This study aimed to further evaluate and confirm the potency of ¹⁸F-FDG PET/CT in diagnosing RP with airway involvement and monitoring response to steroid-based therapy.

Methods

A total of 30 patients from a dedicated respiratory centre, diagnosed with RP in accordance with McAdam, Damiani or Levine criteria, were included in this study. All patients underwent baseline ¹⁸F-FDG PET/CT, and 10 patients underwent second scans after 2.5–15 months of steroid-based therapy. Visual scores (VS) and maximal standard uptake values (SUV_max) were analysed.

Results

In the initial scan, 83.3% (25/30) of patients were found to have FDG uptake in more than one cartilage. The median VS and SUV_max in the cartilages were 3 (range, 1–3) and 3.8 (range, 1.9–17.9), respectively. Positive rates for PET/CT-guided biopsy in nasal, auricular, and tracheal/bronchial cartilages were 100% (5/5), 88.9% (8/9), and 10.5% (2/19), respectively, but the positive biopsy rate in the auricular cartilage was 92.3% (12/13) even without PET/CT assessment. Based on biopsy-proven sites, the sensitivity of PET/CT was 55.6%, and the specificity was 5.3%. Compared with the baseline scan, the second scan showed much lower median VS (2 vs 3, respectively; p < 0.0001) and SUV_max (2.9 vs 3.8, respectively; p < 0.001). Of 10 patients who underwent second PET/CT, 8 had complete therapeutic response, while 2 had partial response.

Conclusion

¹⁸F-FDG PET/CT assists in identifying multiple cartilage involvement in RP, but it seems neither a sensitive nor specific modality in diagnosing RP with airway involvement. Moreover, PET/CT has limited utility in locating biopsy sites and monitoring therapeutic response to corticosteroids.