**9. Conclusions**

Several factors may account for the variable results regarding the impact of crescents on clinical outcomes in IgAN. These include (a) the different patient ethnicities; (b) different timing of the renal biopsy after onset of clinical manifestations; (c) the histologic type of crescents included in each study, either cellular, fibrocellular, or fibrous; (d) the association of crescents with other histopathologic markers of activity, which blunted their independent value; (e) the varying choice of immunosuppressive treatments and dosage regimens; and (f) the different clinical outcomes.

In contrast to the case in some other forms of proliferative glomerulonephritis, the most evident conclusion from the data reported in this review is that crescents do not appear to be an independent predictor of clinical outcomes in patients with IgAN, especially those receiving corticosteroids or other immunosuppressive agents. Although the benefit of such treatment in IgAN with crescents indirectly emerges from this consideration, there is a lack of direct evidence of beneficial effect of corticosteroids or immunosuppressive drugs in every patient with IgAN presenting with crescentic lesions. Over the last decades most severely crescentic cases received corticosteroid-immunosuppressive treatment, and a placebo-controlled RCT in these patients is not conceivable. However, the value of crescents should not be disregarded. An integrated overall consideration including other MEST scores and clinical data and novel biomarkers should be undertaken in achieving a more promising personalized therapeutic approach to IgAN patients.

**Author Contributions:** All authors have contributed equally to the present manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** This review article received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
