The most common causes of fever of unknown
origin are infections, neoplasms, and non-infectious
inflammatory diseases. In this disease group, an
individualized diagnosis algorithm is applied after a
detailed patient history and physical examination. In
our case, comprehensive clinical, biochemical, and
microbiological examinations were performed initially
to determine the etiology of fever. Intensive antibiotic
therapy and aortic valve replacement were performed
due to the diagnosis of infective endocarditis as
evidenced by TE. Fever did not decrease after the
operation and new clinical findings emerged. The
18F-FDG PET/CT was performed which revealed
inflammatory aortitis and polychondritis findings.
In the literature, there are some data indicating
that immunological diseases are triggered, particularly
after heart valve replacement.[6,7] Of note, during
the operation, insertion of a rigid prosthesis to the
fragile position may cause latent inflammation and
stimulate immunological reactions.[7] Relapsing
polychondritis is a systemic autoimmune disease
characterized by progressive inflammation of hyaline
cartilages (ear, nose, peripheral joints, and larynx/
trachea/bronchial tree) and proteoglycan-rich
structures (eye, inner ear, heart, blood vessels, and
kidneys).[1,2] It affects most commonly the nose (90%),
ears (54 to 70%),[8] larynx and tracheobronchial tree
(11 to 69%), joints (18 to 81%), and cardiovascular
system (3 to 27%).[9] The disease usually follows a
relapsing-remitting course. However, the destruction
of the tracheobronchial cartilage may be complicated
by infections. It can cause serious illnesses and even
death. There may be an increase in the anti-collagen
type II and anti-Matrilin-1 antibody. Computed
tomography may be useful in diagnosis. In recent years,
the 18F-FDG PET/CT has been increasingly used for
diagnostic purposes[3,4,8] and follow-up[4] of RPC. This
tool is also useful to localize the biopsy site.[3] The FDG is a radiopharmaceutical that accumulates in cancer
tissues due to increased glucose utilization in neoplastic
cells. However, the increase in glucose metabolism is
not only specific for cancer, but also occurs in inflamed
tissues. Respiratory system is affected in approximately
50% of RPC patients. Mortality and morbidity are
usually associated with respiratory tree involvement.[10]
Cardiovascular complications are the second leading
cause of mortality and morbidity in RPC, accounting
for about one-third of patients. The rate of aortitis is
6.5%.[11] Relapsing polychondritis is rare and, therefore,
it is often overlooked in the differential diagnosis,
leading to unnecessary treatment and interventions.
Currently, there is no RPC-specific laboratory
method or histopathological finding. Relapsing
polychondritis is often diagnosed clinically. When
18F-FDG PET/CT findings are evaluated combined
with clinical findings, it is helpful to determine the
extent of disease and severity of inflammation. In
addition, evaluation of the response to treatment is
also possible using this method.
In conclusion, open heart operations may trigger
autoimmune diseases, such as RPC, or increase the
severity of the existing condition. Polychondritis
findings are typical on 18F-FDG PET/CT. The
Increased uptake of 18F-FDG in cartilages, with
clinical suspicion, should suggest RPC.
Declaration of conflicting interests
The authors declared no conflicts of interest with respect
to the authorship and/or publication of this article.
Funding
The authors received no financial support for the research
and/or authorship of this article.