The significance of ¹⁸F-FDG PET/CT in secondary hemophagocytic lymphohistiocytosis

Abstract

This study was aimed to investigate the significance of ¹⁸F-FDG PET/CT in secondary hemophagocytic lymphohistiocytosis (sHLH) patients. A total of 18 patients received ¹⁸F-FDG PET/CT scan at initial diagnosis. All patients (18/18) had at least 3 organs involved, with increased FDG metabolism in different degrees. Fifteen cases (15/18) had definite underlying diseases, including infections (IAHLH), rheumatosis (RAHLH), or malignancy (MAHLH). The SUV_max of patients in MAHLH group was significantly higher than patients in IAHLH group or RAHLH group (P = 0.015, P = 0.045). Furthermore, the SUV_max of patients in IAHLH group was significantly higher than patients of RAHLH group (P = 0.043). Therefore, we concluded that ¹⁸F-FDG PET/CT may especially play important role in differential diagnosis of sHLH.

To the Editor

Secondary hemophagocytic lymphohistiocytosis (sHLH) is a hyper-inflammatory clinical syndrome mainly caused by severe infections, autoimmune inflammatory disorders and malignancies, especially lymphoma [1–3]. Up to date, very few data from the literature are available regarding the role of ¹⁸F-FDG PET/CT in sHLH. In this study, 18 of 50 patients with sHLH who were admitted into our hospital between May 2007 and December 2010 underwent the examination (Table 1). The male-to-female ratio was 1:1, and the median age was 35 years (15-73). The diagnosis of HLH was made according to HLH-2004 diagnostic guidelines [4, 5], and the underlying diseases were confirmed by a series of pathogenesis examinations including pathology, immunology, bacterial culture and virus detection et al. The maximum standardized uptake values (SUV_max) used to measure the level of FDG uptake were determined in all lesions [6]. All of the 18 patients had at least 3 organs involved, with increased FDG uptake at different level, including 18 cases showing splenomegaly, 16 cases serous effusions, 16 cases lymphadenopathy, 13 cases bone lesions, 12 cases pneumonia, 8 cases hepatomegaly, 5 cases brain parenchymal or cerebroventricular lesions, 5 cases cholecystitis, 4 cases myocardium lesions, and 2 cases kidney calculi. There were also other organs involved, such as larynx, muscles and adnexauteri. Fifteen patients (15/18) had definite underlying diseases, and were divided into three groups.,including Infection Associated HLH (IAHLH, including EBV-HLH, n = 8), Rheumatosis Associated HLH (RAHLH, n = 2), and Malignancy Associated HLH (MAHLH, n = 5). The SUV_max of patients in MAHLH group was significantly higher than those of patients with IAHLH (Mean 12.0 vs. 6.8, P = 0.015), and RAHLH (Mean 12.0 vs. 2.7, P = 0.045). Furthermore, the SUV_max of patients with IAHLH was significantly higher than that of patients with RAHLH (Mean 6.8 vs. 2.7, P = 0.043). However, no significant difference in survival time was found between the three different sHLH subtype according to Kaplan-Meier analysis (P >0.05). In conclusion, ¹⁸F-FDG PET/CT may play important role in differential diagnosis of sHLH, with high SUV pointing toward underlying malignancy.

Table 1 Characteristics of 18 sHLH patients