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OP0035 Circulating Plasmablasts Levels Reflect Inflammatory Activity in IGG4-Related Disease Lesions as Assessed by Quantitative Positron Emission Tomography
  1. A. Berti1,
  2. C. Canevari2,
  3. F. Gallivanone3,
  4. M. Lanzillotta1,
  5. E. Bozzalla Cassione1,
  6. C. Campochiaro1,
  7. G.A. Ramirez1,
  8. M.G. Sabbadini1,
  9. E. Della Torre1
  1. 1Internal Medicine and Clinical Immunology
  2. 2Nuclear Medicine, San Raffaele Scientific Institute, Milan
  3. 3IBFM, CNR, Segrate, Milan, Italy

Abstract

Background IgG4-Related Disease (IgG4-RD) is a systemic inflammatory condition characterized by fibrous swelling of affected organs, serum IgG4 elevation, and IgG4+ plasmacells tissue infiltration. 18-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scan is emerging as a promising imaging technique to detect organs involved by IgG4-RD and to assess disease response to treatment. The relationship between FGD-PET findings and immunological perturbations occurring in IgG4-RD has never been evaluated.

Objectives To correlate the intensity and distribution of FDG-PET uptake with clinical and immunological parameters in patients with active untreated IgG4-RD.

Methods Patients with active, untreated, biopsy proven IgG4-RD were included in the study. Disease activity was assessed through clinical (IgG4-RD Responder Index (RI)) and immunological (erythrocyte sedimentation rate (ESR), C reactive protein (CRP), serum IgG4, and circulating plasmablasts) parameters. Plasmablasts, a recently characterized disease biomarker, were identified as CD19+CD20-CD27+CD38bright cells on flow cytometry. FDG-PET/CT was performed in all patients at diagnosis. Quantitative assessment of FDG uptake was measured using the mean Standardized Uptake Value corrected for the Partial Volume Effect (PVC-SUV). Lymph nodes <1 cm of diameter were excluded from the analysis because of the risk of PVC-SUV over/under-estimation. In patients with multiorgan involvement, the IgG4-RD lesion with the highest PVC-SUV was selected to correlate FGD uptake with clinical and serological parameters.

Results We studied 15 patients (7 males, 8 females) with a mean age of 63 years (range, 30–77 years). Twelve (80%) patients had multiorgan IgG4-RD involving lymphnodes (7 patients); aorta (5 patients); parotids glands and pancreas (3 cases each); bones, skin, thyroid, lung, submandibular and lachrymal glands (2 cases each); meninges, nasal cavity, oropharynx, palate, liver, CNS, and retrorbital space (one case each). The median IgG4-RD RI was 9 (range 6–16; normal =0). The median levels of ESR, CRP, serum IgG4 and plasmablasts at baseline were 30 mm/h (range 6–121 mm/h, normal <20 mm/h), 11.0 mg/L (range 0.0–48.0 mg/L; normal <6mg/L), 284.0 mg/dL (range 45–2100 mg/dL, normal <121 mg/dL), and 3870 cells/mL (range 1000–10000 cells/mL, normal <690 cells/mL), respectively. The median PCV-SUV was 6.24 (range 2.48–16.39). Significant positive correlation was found between PVC-SUV and serum plasmablasts levels (r=.84, p=.004). No correlation was found between PVC-SUV and either CRP, ESR, serum IgG4 levels, number of organs involved, and IgG4-RD RI at baseline (p>.05).

Conclusions Our study demonstrates for the first time a positive correlation between circulating plasmablasts and inflammatory activity in IgG4-RD lesions as assessed by PVC-SUV on FDG-PET. Our results further strengthen the utility of circulating plasmablasts as a biomarker of disease activity. Conventional inflammatory markers, serum IgG4 levels, and IgG4-RD RI do not appear to correlate with metabolic activity in IgG4-RD lesions.

  1. Ebbo M et al. Arthritis Care Res. 2014 Jan;66(1):86–96.

  2. Campochiaro C et al. Scand J Rheumatol. 2015 Sep 23:1–11.

Disclosure of Interest None declared

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