Clinical and Radiologic Differences in Lung Involvement Between IgG4-Related Disease and Plasma Cell-Type Idiopathic Multicentric Castleman Disease.

Purposes: Immunoglobulin G4-related disease (IgG4-RD) and plasma cell-type idiopathic multicentric Castleman disease (PC-iMCD) have many overlapping features. Their differential diagnosis is challenging and crucial for clinical management due to their different prognoses and treatments. However, reports that compare these conditions are scarce, especially for patients with lung involvement. In this study, we attempted to clarify the clinical and radiologic differences in lung involvement between IgG4-RD and PC-iMCD.

Methods: Patients with IgG4-RD or PC-iMCD who exhibited lung involvement were enrolled. Clinical and chest CT findings at baseline were compared.

Results: A total of 178 patients with IgG4-RD and 61 patients with PC-iMCD exhibited lung involvement. The IgG4-RD group consisted of older patients (P < 0.001) and had a higher male‒female ratio (P = 0.004). Patients with PC-iMCD were more inclined to present constitutional and respiratory symptoms, anemia, thrombocytosis and hypoalbuminemia (all P < 0.001). Although IgG4 levels were commonly elevated in both diseases, they were significantly greater in the IgG4-RD (median: 16,100 mg/L) than in the PC-iMCD (median: 3130 mg/L) (P < 0.001). Patients with IgG4-RD showed significantly lower levels of IgG, IgA, IgM (median: 21.59 g/L, 1.70 g/L, and 0.68 g/L, respectively) than in the PC-iMCD (median: 34.42 g/L, 4.85 g/L, and 2.11 g/L, respectively) (all P < 0.001). The levels of CRP, ESR and IL-6 were significantly greater in the PC-iMCD (median: 72.15 mg/L, 103 mm/h, and 18.30 pg/mL, respectively) than that in the IgG4-RD (median: 1.54 mg/L, 22 mm/h, and 2.85 pg/mL, respectively) (all P < 0.001). Although both nodular lesions and thickened bronchovascular bundles were common in these two diseases, PC-iMCD patients presented more extensive nodular lesions (P < 0.001), and IgG4-RD patients presented more diffuse thickened bronchovascular bundles (P < 0.001). Cysts were almost exclusively observed in PC-iMCD patients.

Conclusions: Compared with IgG4-RD, PC-iMCD is a more aggressive condition, associated with more common symptoms and more severe inflammation. Radiologically, extensive nodular lesions or cysts suggest a diagnosis of PC-iMCD, whereas diffuse thickened bronchovascular bundles indicate a diagnosis of IgG4-RD.