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Background Hemophagocytic lymphohistiocytosis (HLH) is a nonmalignant disorder of immune regulation, with overproduction of cytokines and diminished immune surveillance. Symptoms are nonspecific and may affect multiple organs, including the central nervous system. Neuroimaging findings have been described in case reports and small series; body imaging findings have not been described extensively. Objective To summarize findings of the most frequently performed imaging studies of the brain, chest and abdomen in patients with HLH. Materials and methods Retrospective review of chest radiographs and CT, abdominal ultrasound and CT, brain CT and MRI, skeletal surveys, and autopsy data. Results Twenty-five patients were diagnosed and treated for HLH at our institution over an 11-year period; 15 patients (60%) died. Common chest radiograph findings included alveolar-interstitial opacities with pleural effusions, often with rapid evolution and resolution. Hepatosplenomegaly, gallbladder wall thickening, hyperechoic kidneys and ascites were common abdominal findings, which resolved after therapy in some cases. Brain-imaging studies revealed nonspecific periventricular white-matter abnormalities, brain-volume loss and enlargement of extra-axial fluid spaces. Three infant cases, one with intracranial hemorrhage, one with multiple pathologic rib fractures and one with diaphyseal periosteal reaction involving multiple long bones on skeletal survey, raised suspicion of child abuse at presentation. Abuse was not substantiated in any case. Conclusions Clinicians and radiologists should be aware of the radiographic manifestations of HLH, which are nonspecific and overlap with infectious, inflammatory and neoplastic disorders. Findings in the chest (similar to acute respiratory distress syndrome) and abdomen may progress rapidly and then regress with institution of appropriate anti-HLH therapy. CNS findings may be progressive. In some infants, initial imaging findings may mimic nonaccidental trauma.

Objective. To determine the frequency of thymic involvement in Langerhans' cell histiocytosis and describe its imaging appearance before and after treatment. Materials and methods. A retrospective review of the radiology and clinical records of all patients diagnosed with Langerhans' cell histiocytosis at DeVos Children's Hospital between 1992 and 1998. Results. Of the 14 patients diagnosed with Langerhans' cell histiocytosis, 7 demonstrated multisystem involvement. The thymus was involved in 5 of 7 patients. The thymus was enlarged in 5; thymic contours were nodular/lobulated in 2; cystic changes were noted in 4; and dystrophic vascular-appearing calcifications were seen in 1. In all cases, findings regressed or resolved following chemotherapy. Conclusion. The thymus is commonly involved in Langerhans' cell histiocytosis, especially in multisystem disease. Radiologically, the thymus is enlarged and may be smooth or lobulated/nodular in contour, possibly containing cysts and calcifications.