1. AbstractPulmonary involvement is a common manifestation of Dermatomyositis (DM), the most frequent histologic pattern being Interstitial Lung Disease (ILD) which is a major contributor to morbidity and mortality in these patients. Therefore, this disease should be investigated and it is essential to perform pulmonary function tests (PFTs) and High-Resolution ComputedTomography (HRCT) early in the course of the disease to make a definitive diagnosis.Nowadays,2-deoxy-2-[18F]fluoro-D-glucosepositron emission tomography/computed tomography (2-[18F]FDG PET/ CT) can be a useful tool for patients diagnosed with DM since,in addition to observing the state of inflammatory myopathy and detecting possible associated malignant tumors, it allows early identificationofILD,beforestructuralchangesoccur.Wepresent the case of a 45-year-old patient with a diagnosis of DM, who requested 2-[18F]FDG PET/CT to rule out possible occult neolasia, showing pathological uptake of moderate intensity and peripheral predominance in the posterior segments of both lower lobes that coincides with a very discrete increase in pulmonary interstitial density, which translates as an active inflammatory pathology, to rule out ILD.Given the findings on 2-[18F]FDG PET/CT, it was decided to perform a HRCT showing pulmonary interstitial involvement with reticular pattern and ground glass, predominantly peripheral and basal, suggest ILD. PFTs showed a progressivedropinKCO(71%),so,inviewofthesefindings,ILD wasdiagnosedandimmunosuppressivetreatmentwasprescribed. AcontrolCTwasperformedshowingimprovementoftheinterstitialinvolvement.Currentlythepatientisclinicallyasymptomatic, withoutPFRalteration(KCO75%)andILDradiologystability.In conclusion 2-[18F]FDG PET/CT can help in the early diagnosis, clinical course and treatment of ILD in patients with DM.
2. IntroductionDermatomyositis (DM) is included within the idiopathic inflammatorymyopathiesoridiopathicmyositiswhicharecharacterized asaheterogeneousgroupofmusclediseasesofunknownetiology that cause progressive onset of muscle weakness, inflammation and may cause systemic involvement. Pulmonary involvement appears to be a common manifestation, the most frequent histological pattern being Interstitial Lung Disease (ILD).About 35-40% of patients will develop ILD throughout the course of their disease [1]. ILD is known to be an important contributor to morbidity and mortality in these patients, with a 5-year survival rate of 50% 2 Therefore, due to the important effect that ILD has on mortality in patients with DM, this disease should be investigated, and it is essential to perform Pulmonary FunctionTests(PFTs)atthebeginningofthecourseofthedisease, sincetheyusuallyshowreducedlungvolumes,impairedgastrans- fer and hipoxemia, however, these tests may vary significantly as muscle strength improves with treatment, and High-Resolution ComputedTomography(HRCT)isnecessarytomakeadefinitive diagnosis [3]. Nowadays, 2-deoxy-2-[18F] fluoro-D-glucose positron emission tomography/computedtomography(2-[18F]FDGPET/CT)canbe ausefultoolforpatientsdiagnosedwithDM,since,inadditionto observing the state of inflammatory myopathy and detecting possibleassociatedmalignanttumors,itallowsILDtobeidentified early,beforestructuralchangesoccur.InILD,anincreaseinmacrophages,lymphocytesandthereleaseofcytokinessuchasTNF-α andIL-2hasbeendescribed,whichcausesanincreaseinglycemic metabolismthat,using18F-FDGasaradiotracer,canbedetected byPET/CT,obtainingearlyinformationonthispathologywhichis relatively frequent and which negatively influences the prognosis of these patients [4, 5].
3. Case PresentationWepresentthecaseofa45-year-oldfemalepatientwithadiagnosisofDM,whoattendedaconsultationfordiseasecontrol.Shedid notreferrespiratorysymptoms.Onphysicalexaminationbasalsaturation of 98%, without alteration when exploring the cardiopulmonarysystem.Laboratorytestswithinthenormalrange.Positive Antinuclear Antibodies (ANA). Chest X-ray without alterations. 2-[18F]FDGPET/CT(july/2019)wasrequestedtoruleoutpos sible occult neoplasm, showing pathological uptake of moderate intensity and peripheral predominance in the posterior segments of both lower lobes, coinciding with a very discrete increase in pulmonaryinterstitialdensity,whichtranslatesasanactiveinflammatory pathology, to rule out ILD (Figure 1). Giventhefindingspresenton2-[18F]FDGPET/CT,itwasdecided to perform a HRCT (august/2019) of the chest and PFTs. HRCT showed pulmonary interstitial involvement with reticular pattern and ground glass, predominantly peripheral and basal, suggest ILD (Figure 1). PFTs showed a progressive drop in KCO (71%), so,inviewofthesefindings,ILDwasdiagnosedandimmunosuppressive treatment was prescribed. A control CT was performed (october/2020) showing improvement of the interstitial involvement.Currentlythepatientisclinicallyasymptomatic,withnoalterationofPFTs(KCO75%)andstableILDradiology(Figure1).
4. DiscussionILDoccursfrequentlyinDMandisanimportantcauseofmortali - ty,beingitsearlydiagnosisparamount.However,earlychangesof asymptomatic ILD are difficult to detect. Interestingly,PET/CTshowedamoderateincreasein2 -[18F]FDG uptake in the periphery of the lung bases, before the detection of alteredPFTs,suggestingactiveinflammatorydisease.Inaddition, itwasevidencedthatoncetheHRCTwasperformed,thelocation of the increased uptake in [18F] FDG PET/CTcoincidedwith the location of the interstitial lung involvement seen in HRCT. There is evidence in the literature that 2 -[18F]FDG PET/CT can aid in the early diagnosis of ILD prior to detection by HRCT 5 coincidingwiththelocationofinterstitiallunginvolvement6.Fur - thermore, it indicates that increased metabolic activity suggests active disease and its changes suggest response to treatment, thus reflecting the degree of disease activity [7, 8].
5. Conclusion 2-[18F]FDGPET/CTcanhelpintheearlydiagnosis,clinical course and treatment of ILD in patients with DM
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OrtizSG.Early Detection of Interstitial Lung Disease in Asymptomatic Patients with 2-[18F] FDG PET/CT . Annals of Clinical and Medical Case Reports 2022