{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T11:21:20Z","timestamp":1785410480309,"version":"3.56.0"},"reference-count":12,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T00:00:00Z","timestamp":1779840000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Chonnam National University Hospital Biomedical Research Institute","award":["BCRI-26057"],"award-info":[{"award-number":["BCRI-26057"]}]},{"award":["BCRI-26057"],"award-info":[{"award-number":["BCRI-26057"]}],"id":[{"id":"https:\/\/ror.org\/00f200z37","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Relapsing polychondritis (RP) is a rare autoimmune disease of cartilaginous structures, often diagnosed late due to nonspecific presentations. Both RP and granulomatosis with polyangiitis (GPA) can cause diffuse tracheobronchial wall thickening on computed tomography (CT) and may be seronegative for anti-neutrophil cytoplasmic antibody (ANCA), creating a diagnostic impasse. We report a 46-year-old man with two months of fever, productive cough, and sternal pain. A saddle nose deformity was the only cartilaginous sign; serum ANCA was repeatedly negative. Neck CT showed diffuse tracheal and bilateral main bronchial wall thickening; the report listed amyloidosis and GPA as differential diagnoses, omitting RP. Despite laboratory, microbiological, and imaging workup, the fever fulfilled criteria for fever of unknown origin (FUO), prompting 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)\/CT. PET\/CT demonstrated intense FDG uptake in the cartilaginous wall of the tracheobronchial tree, forming the classic inverted-Y sign, with bilateral costal cartilage hypermetabolism (a site not involved in GPA) and no uptake in the kidneys, sinuses, or orbits, collectively establishing a diagnosis of RP. Corticosteroid therapy elicited prompt clinical and biochemical response. This case demonstrates that 18F-FDG PET\/CT can differentiate RP from GPA when CT and serology are uninformative.<\/jats:p>","DOI":"10.3390\/diagnostics16111634","type":"journal-article","created":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T11:03:27Z","timestamp":1779879807000},"page":"1634","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Relapsing Polychondritis Mimicking ANCA-Negative Granulomatosis with Polyangiitis: Diagnostic Value of 18F-FDG PET\/CT"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3610-1957","authenticated-orcid":false,"given":"Ki-Seong","family":"Park","sequence":"first","affiliation":[{"name":"Department of Nuclear Medicine, Chonnam National University Hospital, Gwangju 61469, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5931-5726","authenticated-orcid":false,"given":"Sung Un","family":"Shin","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Chonnam National University Hospital, Gwangju 61469, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1373-1887","authenticated-orcid":false,"given":"Sang-Geon","family":"Cho","sequence":"additional","affiliation":[{"name":"Department of Nuclear Medicine, Chonnam National University Hospital, Gwangju 61469, Republic of Korea"},{"name":"Department of Nuclear Medicine, Chonnam National University Medical School, Gwangju 58128, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4077-7722","authenticated-orcid":false,"given":"Jahae","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Nuclear Medicine, Chonnam National University Hospital, Gwangju 61469, Republic of Korea"},{"name":"Department of Nuclear Medicine, Chonnam National University Medical School, Gwangju 58128, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ho-Chun","family":"Song","sequence":"additional","affiliation":[{"name":"Department of Nuclear Medicine, Chonnam National University Hospital, Gwangju 61469, Republic of Korea"},{"name":"Department of Nuclear Medicine, Chonnam National University Medical School, Gwangju 58128, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"241","DOI":"10.1186\/s13075-022-02935-2","article-title":"Differentiating Tracheobronchial Involvement in Granulomatosis with Polyangiitis and Relapsing Polychondritis on Chest CT: A Cohort Study","volume":"24","author":"Jalaber","year":"2022","journal-title":"Arthritis Res. Ther."},{"key":"ref_2","first-page":"000625","article-title":"ANCA-Negative Granulomatosis with Polyangiitis: A Difficult Diagnosis","volume":"4","author":"McCarthy","year":"2017","journal-title":"Eur. J. Case Rep. Intern. Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1007\/s13139-024-00894-x","article-title":"18F-FDG PET\/CT in Inflammation and Infection: Procedural Guideline by the Korean Society of Nuclear Medicine","volume":"59","author":"Choi","year":"2025","journal-title":"Nucl. Med. Mol. Imaging"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1482","DOI":"10.1093\/rheumatology\/keu147","article-title":"Utility of Fluorodeoxyglucose Positron Emission Tomography\/Computed Tomography for Early Diagnosis and Evaluation of Disease Activity of Relapsing Polychondritis: A Case Series and Literature Review","volume":"53","author":"Yamashita","year":"2014","journal-title":"Rheumatology"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1093\/rheumatology\/kez243","article-title":"Fluorodeoxyglucose Positron Emission Tomography\/Computed Tomography in the Diagnosis, Assessment of Disease Activity and Therapeutic Response in Relapsing Polychondritis","volume":"59","author":"Sharma","year":"2020","journal-title":"Rheumatology"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"153","DOI":"10.4103\/ijnm.IJNM_151_18","article-title":"18F-Fluorodeoxyglucose Positron Emission Tomography\/Computed Tomography in the Assessment of Occult Involvement in Widespread Granulomatosis with Polyangiitis (Wegener\u2019s Granulomatosis)","volume":"34","author":"Alqarni","year":"2019","journal-title":"Indian J. Nucl. Med."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"198","DOI":"10.1186\/s13075-023-03156-x","article-title":"Imaging Features and Clinical Value of 18F-FDG PET\/CT for Predicting Airway Involvement in Patients with Relapsing Polychondritis","volume":"25","author":"Yi","year":"2023","journal-title":"Arthritis Res. Ther."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Borgia, F., Giuffrida, R., Guarneri, F., and Cannav\u00f2, S.P. (2018). Relapsing Polychondritis: An Updated Review. Biomedicines, 6.","DOI":"10.3390\/biomedicines6030084"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"74","DOI":"10.7326\/0003-4819-104-1-74","article-title":"Relapsing Polychondritis: Survival and Predictive Role of Early Disease Manifestations","volume":"104","author":"Michet","year":"1986","journal-title":"Ann. Intern. Med."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"929","DOI":"10.1288\/00005537-197906000-00009","article-title":"Relapsing Polychondritis\u2014Report of Ten Cases","volume":"89","author":"Damiani","year":"1979","journal-title":"Laryngoscope"},{"key":"ref_11","first-page":"2181","article-title":"Incidence and mortality of relapsing polychondritis in the UK: A population-based cohort study","volume":"54","author":"Hazra","year":"2015","journal-title":"Rheumatology"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"20150695","DOI":"10.1259\/bjr.20150695","article-title":"18F-FDG PET-CT: A Powerful Tool for the Diagnosis and Treatment of Relapsing Polychondritis","volume":"89","author":"Lei","year":"2016","journal-title":"Br. J. Radiol."}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/11\/1634\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T11:25:03Z","timestamp":1779881103000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/11\/1634"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,27]]},"references-count":12,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2026,6]]}},"alternative-id":["diagnostics16111634"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics16111634","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,27]]}}}