‘Tree-in-Bud’: Thinking beyond Infectious Causes

High-resolution computed tomography is an important diagnostic instrument in pneumology. The ‘tree-in-bud’ sign is a common finding in HRCT scans. The list of the most frequent differential diagnoses for ‘tree-in-bud’ sign includes infections with Mycobacterium tuberculosis, nontuberculous mycobacteria, and other bacterial, fungal, or viral pathogens. Other causes could be immunological, congenital, and idiopathic Received: August 25, 2014 Accepted after revision: November 15, 2014 Published online: Janu ary 21, 2015 Elena Terhalle Research Center Borstel Leibniz Center for Medicine and Biosciences Parkallee 35, DE–23845 Borstel (Germany) E-Mail eterhalle @ fz-borstel.de © 2015 S. Karger AG, Basel 0025–7931/15/0892–0162$39.50/0 www.karger.com/res Established Facts • The two most common pulmonary complications in patients with leukemia are hemorrhage and infectious infiltrates. • The entities showing a ‘tree-in-bud’ sign on high-resolution computed tomography are most frequently associated with infectious causes, but immunological, congenital, and idiopathic disorders as well as aspiration, inhalation of toxic agents, and pulmonary vascular diseases may also cause it.