Can We Differentiate Between Primary Sjögren Syndrome and Idiopathic Multicentric Castleman Disease Based on the Characteristics of Pulmonary Cysts?

PURPOSE: To identify radiological characteristics that could help differentiate cystic lung diseases between primary Sjögren syndrome (pSS) and idiopathic multicentric Castleman disease (iMCD).

PATIENTS AND METHODS: Patients with pSS or iMCD who had cysts were enrolled. Cyst characteristics (number, size, morphology, and distribution) and other accompanying manifestations (nodules, ground-glass opacities, calcification, and thickening of the bronchovascular bundles and interlobular septa) were compared between them.

RESULTS: Eleven patients with pSS and 25 patients with iMCD were eligible for our study. Eleven patients with pSS (100.0%) and 23 patients with iMCD (92.0%) had round or oval cysts. None of the patients with pSS had irregular cysts, but 21 (84.0%) patients with iMCD had irregular cysts (P = 0.005). Smooth-walled cysts were present in 11 patients with pSS (100.0%) and 18 patients with iMCD (72.0%). Only 1 patient with pSS (9.1%) exhibited non-smooth-walled cysts, whereas 23 patients with iMCD (92.0%) had non-smooth-walled cysts (P = 0.003). The presence of nodules was common in both groups (P = 1.000). However, the nodules were more likely to be larger and more numerous in patients with iMCD (P < 0.001). Cysts with mural nodules (52.2%) and central nodules (47.8%) were only observed in iMCD (P = 0.007).

CONCLUSION: Although regular and smooth-walled cysts were common in the 2 diseases, irregular and non-smooth-walled cysts were more often associated with iMCD than pSS. Nodules in iMCD tended to be larger and more numerous, and a close positional relationship between nodules and cysts was only observed in iMCD.