A 46-year-old female nonsmoker with metastatic lung cancer, who was currently on targeted therapy with lorlatinib, presented with a four-week history of progressive dyspnea.
 
Physical examination revealed reduced breath sounds in the left lung and an SpO2 drop to 94%. Pulmonary function tests showed a restrictive ventilatory pattern. An FDG-PET/CT scan demonstrated increased FDG uptake in the right diaphragm, a finding that was absent on prior imaging. Given the manifest signs of cervical disease progression, a diagnosis was established of left phrenic nerve compression leading to left diaphragmatic elevation and a subsequent compensatory increase in the work of the functioning side and to increased FDG uptake in the right diaphragm (Figure 1).
 

 
Increased FDG uptake is generally attributable to muscle activity, surgical interventions, or inflammatory conditions.(1) In the context of pulmonary pathology, bilateral FDG uptake in the diaphragm is typically secondary to hyperventilation.(2) However, unilateral FDG uptake is predominantly indicative of contralateral diaphragmatic paralysis. Contralateral FDG uptake is a compensatory physiological response that should not be misdiagnosed as malignant, a condition that is notably rare.(1,3)
 
FINANCIAL SUPPORT
 
None.
 
AUTHOR CONTRIBUTIONS
 
FMC, MAFMF, and AKM: study conception, planning, and design; and data collection. FMC and MAFMF: writing of the preliminary drafts and final version of the manuscript. FMC, MAFMF, and AKM: revision of the manuscript. All authors read and approved the final version of the manuscript.
 
CONFLICTS OF INTEREST
 
None declared.
 
REFERENCES
 
1.  Joshi P, Lele V. Left is right and right is wrong: Fluorodeoxyglucose uptake in left hemi-diaphragm due to right phrenic nerve palsy. Indian J Nucl Med. 2013;28(1):32-33. 10.4103/0972-3919.116812
2.  Cook GJ, Wegner EA, Fogelman I. Pitfalls and artifacts in 18FDG PET and PET/CT oncologic imaging. Semin Nucl Med. 2004;34(2):122-133. 10.1053/j.semnuclmed.2003.12.003
3.  Benameur Y, Ait Sahel O, Nabih Oueriagli S, Doudouh A. Infection of implantable car-diac defibrillator [Article in French]. Rev Prat. 2020;70(3):235.