Radiological Manifestations of Scrub Typhus

Introduction Scrub typhus is a potentially fatal infectious disease caused by the organism Orientia tsutsugamushi. It may clinically present as acute flu like syndrome, hepatic dysfunction, pulmonary involvement, cardiovascular, renal dysfunction, aseptic meningitis and multiorgan involvement. A high degree of clinical suspicion and knowledge of the various radiologic manifestations of scrub typhus allow an early diagnosis and timely initiation of appropriate therapy, and thereby may help reduce patient morbidity and mortality.The radiologic findings of scrub typhus are varied and nonspecific (1). Nevertheless, an awareness of the related findings at imaging (X-ray, ultrasound, MRI & especially computed tomography (CT)) may facilitate accurate diagnosis. Pulmonary Findings The reported incidence of chest radiographic abnormalities in patients with scrub typhus varies from 59% to 72% (1, 2). The pulmonary manifestations of scrub typhus include interstitial pneumonia, interstitial edema, and hemorrhage caused by vasculitis. Interstitial pneumonia (IP) frequently occurs in patients with scrub typhus and is closely associated with severity of the disease. The recognition of the presence of Interstitial Pneumonia is an important determining factor for predicting the clinical course and prognosis for patients with scrub typhus. Bilateral diffuse areas of reticulonodular opacity (Fig-1) and septal lines are the most common findings (1, 2). Airspace consolidation is relatively uncommon and generally appears in the lower zone of both lungs (1, 2). Unilateral or bilateral hilar enlargement and pleural effusion are common radiographic features, found in 25%-27% and 12%-43% of patients, respectively (1, 2). Ground-glass opacity, interlobular septal thickening and pleural effusions are common findings at thin-section CT (Fig-2), whereas bronchial wall thickening, centrilobular nodules and axial interstitial thickening are less common. Contrast-enhanced chest CT images in most cases depict mediastinal and axillary lymphadenopathy (short axis diameter of more than 10 mm). A very serious complication of scrub typhus is acute respiratory distress syndrome (Fig-3). It is rare and may occur in older age group patients with thrombocytopenia, and presents with radiographic evidence of early pneumonitis (3). Cardiac Findings Myocardial lesions were observed in 80% of patients in one autopsy series (4). Interstitial myocarditis may occur in scrub typhus. Cardiomegaly, which may be due to myocardial or pericardial involvement in the infection (57), is usually reversible (1). Congestive cardiac failure is SCRUB TYPHUS EMERGING THREAT CLINICAL IMAGES