While the clinical, biological and radiological characteristics of several series of CVID–GD patients have been described [6, 8, 10], and even compared to those of classical sarcoidosis [18, 19], none has focused on the blood immunological phenotype and the histological differences between the two diseases. Because granulomatosis diagnosis may precede that of CVID, it is important for both clinicians and pathologists to have markers suggesting the possible CVID in the presence of granulomatosis. Hence, this work was undertaken to compare CVID-GD and sarcoidosis characteristics to identify features suggestive of CVID-GD, primarily searching for immunological and histological differences. For this purpose, we included all CVID patients, whose organ biopsies contained GD, and sarcoidosis patients, followed in our department, and who had available sufficient tissue material and retrospective blood lymphocyte immunophenotyping.
CIVID-GD is characterized by non-caseating granulomas potentially involving any organ and occurs in 8–22% of CVID patients [3, 5, 10, 13], and 13.5% in the French DEFI cohort with slight female predominance . In that cohort, the median age of GD onset was 40 years, and was most often diagnosed after CVID (median, 2.1 years later), although some cases may precede CVID development. Consanguinity, autoimmune cytopenias and splenomegaly were more frequent in CVID-GD patients than those without GD. The lung was the most prominent GD localization, although other extrathoracic organs were also involved, mainly liver and spleen, more frequently than in sarcoidosis. Globally, although modest in size, our patient sample well reflects this clinical pattern.
Three laboratory parameters differed significantly between the two diseases: 1) blood platelet level was lower in CVID, probably because some patients also had ITP and others had splenomegaly; 2) ACE levels were higher in CVID, but no difference was observed in the Bouvry et al.’s larger cohort of , probably because high raised levels of ACE may be more documented in sarcoidosis; 3) and blood total gamma-globulin levels were dramatically higher in sarcoidosis. None of our patients had hypercalcemia.
Based on thoracic CT scans, Bouvry et al.  showed CVID lung involvement to be characterized by large randomly distributed nodules, preferentially localized in the lower lung zones, in the presence of air bronchograms and smooth margins surrounded by ground-glass opacities (halo sign) and bronchiectasis. Moreover, the usual micronodules distribution observed in sarcoidosis was significantly less frequent in CVID-GD than sarcoidosis (100% vs. 42%, respectively). We did not compare radiological profiles because sarcoidosis patients were not matched with CVID-GD patients for radiographic granulomatosis staging.
Notable immunological differences were found between CVID-GD and sarcoidosis patients. First, circulating naïve B-lymphocytes were significantly higher and circulating smB− cells drastically lower. Previous study results showed a correlation between fewer peripheral smB− cells and granulomatosis, especially when associated with splenomegaly [15, 20]. Although described in sarcoidosis vs. healthy controls , none of our patients with sarcoidosis has lower smB− cell counts. The lowest percentage of smB− cells in our sarcoidosis patients always remains higher than the highest percentage observed in CVID patients. Second, the percentage of activated, blood T lymphocytes (predominantly CD8+) was significantly higher in CVID than sarcoidosis, which was characterized by comparably lower percentages of CD4+ and CD8+ subpopulations. In this study, we established a strong association between CVID-GD and increased CD8+ T-cell activation, thereby consolidating the important link between T-cell activation and clinical complications we previously assessed . Third, we confirmed elevated blood TFH cells in CVID-GD patients, with a skewing toward TFH1 cells in contrast to TFH2 and TFH17 populations, while peripheral TFH-subpopulation distributions of healthy controls and sarcoidosis patients did not differ. We previously showed an inverse correlation between circulating TFH1 and smB− cells, mainly in CVID patients with non-infectious complications including GD . Thus, the immunological profile of CVID-GD patients differs markedly from that of sarcoidosis patients, with a profound memory-cell deficit, strong CD8+ T-cell activation and altered TFH-subset balance in blood.
CVID GD morphology from patients differ from that of sarcoidosis. Granulomas in the latter are often uniform in appearance, non-necrotizing, tend to become confluent adjacent to each other and, in older cases, exhibit a peripheral rim of hyalinization or fibrosis . In CVID, granulomas vary in size, are arranged concentrically, either in a crown around a reactive follicle or surrounded by a dense lymphocytic infiltrate. This lymphoid proliferation is not observed in sarcoidosis. We previously described this histological pattern in the spleens of several CVID patients , but showed herein that it also concerns other organs, such as lymph nodes and skin. These features should alert the pathologist analyzing granuloma to suggest a CVID-like disease. Moreover, we previously described an accumulation of TFH1 cells in the spleen of CVID patients , and confirmed that observation herein; moreover, TFH1 cells were also seen in other tissues with GD, e.g., skin or lymphadenopathy. That represents a notable distinction with sarcoidosis.
Finally, granuloma-formation processes in CVID remain unelucidated and it is unknown whether they resemble those in sarcoidosis. Several groups demonstrated constitutively upregulated JAK-STAT–signaling in sarcoidosis, attributed to increased production of cytokines, mainly interferon-gamma (IFN-γ) by T lymphocytes [24–26]. The results of several studies on sarcoidosis showed constitutive activation of JAK-STAT–signaling at the messenger RNA level in peripheral blood mononuclear cells and other tissues, and found constitutive activation of STAT1 and STA3 proteins in granulomas [25, 27]. To determine whether the same pattern occurred in the CIVD granuloma, we undertook IHC-labeling studies on different archival tissue samples to assess activated JAK-STAT signaling (with p-STAT1 and p-STAT3). As in sarcoidosis, CVID granuloma exhibited a similar pattern of p-STAT1 and p-STA3 activation. Therefore, this constitutive activation of the JAK-STAT pathway may be a conserved feature of granulomatous disorders. These results suggest that JAK-STAT–pathway inhibition could be a promising therapeutic approach for CVID-GD patients, as recently reported for several cases of refractory sarcoidosis, including long-standing multiorgan disease, which had been successfully treated with the oral JAK (JAK1 and JAK3) inhibitor tofacitinib [27–29]. Corticosteroids are the gold-standard therapy for CVID-GD, but complete response is infrequent and their long-term side effects preclude their long-term use. Other immunosuppressive drugs have been used with varying degrees of efficacy but no therapeutic combination has demonstrated superiority, although rituximab is commonly used prescribed for associated lymphoproliferation. Thus, tofacitinib efficacy and safety in CVID-GD patients should be evaluated.
We are well-aware that our study has several limitations. Our patient sample is small but CVID-GD remains a rare disease for which it is difficult to recruit many patients. Our control population was arbitrary and we selected only patients admitted to our department for sarcoidosis, with sufficient tissue material available, several organs affected to closely resemble the systemic form, and retrospective immunological phenotyping, criteria not met by our entire sarcoidosis cohort. However, this selected group reflects the heterogeneity of the sarcoidosis. The differences observed between the two study populations seem homogeneous despite the small number of patients.
In conclusion, our results established several differences between CVID-GD and sarcoidosis, some of which had never been reported previously, mainly in terms of histology, allowing a pathologist to evoke CVID-GD in the presence of tissue granulomatosis. Nevertheless, the mechanism of macrophage activation seems to be the same as in sarcoidosis, suggesting possible use of agents blocking the JAK-STAT pathway in CVID-GD, which remains difficult-to-treat.