Glomerular crescents

Glomerular crescents is the appearance of a histopathological lesion with extracapillary proliferation in the glomeruli (Jung 2020).

It is a hyperplastic lesion that may account for 10% or more of the circumference of Bowman's capsule (Anguiano 2020).

One differentiates, depending on the composition between:

- Cellular crescent

Here 75% cells and fibrin are found and less than 25% fibrous matrix.

- Fibrocellular crescent

This is characterized by 25-75% cells and fibrin, with the remainder fibrous matrix.

- Fibrous crescent

This is characterized by 75% fibrous matrix with less than 25% cells or fibrin (Anguiano 2020).

Glomerular crescents can occur in a variety of glomerular diseases, collectively known as crescentic glomerulonephritis (CGN) such as:

- Rapid progressive glomerulonephritis (RPGN) (Young 2020).

- mesangioproliferative gl omerulonephritis with diffuse crescent formation (MESPGN- DH), also referred to as "idiopathic crescent glomerulonephritis"

- glomerulonephritis in Schönlein- Henoch purpura (Remmele 1984)

- anti-glomerular basement membrane disease (McAdoo 2017).

Cellular crescents develop from activated parietal epithelial cells (PECs). There are several molecular pathways that trigger this activation. These include, for example, microvascular injury leading to rupture of the glomerular basement membrane, resulting in leakage of plasma proteins with hyperplasia of parietal epithelial cells (Anguiano 2020).

The crescents are located along the Bowman capsule. Due to its formation, there is a decrease in glomerular filtration rate.

The cellular crescents are still reversible at an early stage. However, as soon as the multistage growth of activated parietal epithelial cells is accompanied by a change in cell phenotype and fibrous crescents form, they are irreversible (Anguiano 2020).

Glomerular crescents are thus usually the result of an intense immune attack involving cytotoxic elements (Anguiano 2020).

Glomerular crescents are found on histologic examination as extracapillary proliferative foci in various glomerular diseases of the kidney (Jung 2020).

They consist of a variable mixture of cells, fibrin, and fibrous matrix (Anguiano 2020) and are designated differently, depending on their composition (see "Classification").

In a study using a mouse model, Melica et al. (2022) showed that panobinostat administration reduced the number of crescent formation and showed significant improvement in renal function including proteinuria.

Panobinostat has previously been used to treat hematopoietic stem cell disorders (Melica 2022).

Disease in which more than 50% of the glomeruli show crescents is associated with a poor prognosis in terms of renal function and patient survival (Melica 2022).

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