**3.1 Classification criteria of ANCA-associated vasculitis:**

## *3.1.1 Granulomatosis with polyangiitis*

Granulomatosis with polyangiitis (GPA), formerly named Wegner's disease, is characterized by vessel wall inflammation, peri- and extra-vascular granulomatosis. Its annual incidence is 10.2 cases per million people, and its prevalence is between 24 and 150 cases per million people [9]. Caucasians are the most affected persons according to researches conducted in Europe [10]**.** GPA is diagnosed at an age of 35–55 years with no gender predominance.

This disease involves mainly upper and lower airways, ear nose throat sphere and kidney. Nasosinus involvement occurs in 70–100% of patients as epistaxis, nasal septum deformation or perforation [11, 12]. Lungs manifestations affect 50–90% of the patients as lung nodules, cavitations, pleuritis and/or alveolar hemorrhages. Renal involvement affects 40–100% of patients as abnormalities in urine sediment and renal failure. Other systemic manifestations may include arthralgia, anorexia, weight loss, ocular involvement (episcleritis, uveitis, retinal thrombosis, orbital pseudotumor…) myocarditis [11]**.** Recently, a new criteria set has been approved and validated by the American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR). The aim of the classification criteria is to differentiate GPA from other types of small- or mediumvessel vasculitis (**Table 1**) [13]**.**

A limited form of GPA is defined by the presence of upper airways and/or pulmonary involvement without alveolar hemorrhage. There is no renal involvement or life-threatening conditions.

A diffuse or severe form of GPA is known by the presence of a severe renal dysfunction and/or progressive alveolar hemorrhage and/or life-threatening organ involvement.


#### **Table 1.**

*2022 American college of rheumatology (ACR)/European alliance of associations for rheumatology [13].*

#### *3.1.2 Eosinophilic granulomatosis with polyangiitis*

Eosinophilic granulomatosis with polyangiitis (EGPA) formerly known as Churg– Strauss syndrome is a rare systemic small-vessel vasculitis associated with asthma and eosinophilia. EGPA is the least common systemic vasculitis among AAV with an annual incidence of 4.2 cases per million people and a prevalence of 10.7 per million people [14]**.** It affects people aged between 40 and 60 years with no gender predominance or ethnic predisposition [15, 16]**.** In 1990, ACR defined the classification criteria for EGPA including asthma, eosinophilia >10%, neuropathy, non-fixed lung infiltrates, paranasal sinus abnormalities and extravascular eosinophils on biopsy (**Table 2**) [17]. EGPA should be suspected in a patient with an adult-onset asthma and multiple systemic manifestations (asymmetric neuropathy, purpura or skin ulcers, cardiac, pulmonary and/or renal involvement …). Laboratory data show mainly peripheral eosinophilia (>1500 cells/μL) correlated with the disease activity [18]**.** MPO-ANCA with perinuclear Immunofluorescence (pANCA) are noted in 50% [5]**.** Histologic findings confirm the leukocytoclastic vasculitis with eosinophilic granulomas in different biopsy sites (lung, kidney…).

#### *3.1.3 Microscopic polyangiitis*

MPA is a systemic necrotizing vasculitis with a pneumo-renal tropism. Capillaritis is the cause of its main feature including alveolar hemorrhage and rapidly progressive glomerulonephritis. The annual incidence of MPA is about 5.8 cases per million people [14]. MPA affects older patients compared to other AAV (between 50 and 60 years) [19]. Some studies suggest that increased life expectancy may contribute to the increased incidence of this disease [20]. Men are more frequently affected than women [14]. Other clinical manifestations may include general signs (fever, weight loss) in 70% of patients, skin lesions as vascular pupura, peripheral neuropathy, liver dysfunction and gastrointestinal manifestations. MPO-ANCA are detected in about 50% of cases, but its absence does not exclude its diagnosis [5]**.** Histological data allow the differentiation of MAP from other AAV. This entity is characterized by the absence of eosinophilic tissue infiltration found in GEPA and granulomas found mainly in GPA but also in GEPA.

#### *3.1.4 Five-factor score: a prognosis score of ANCA-vasculitis*

The five-factor score (FFS) for AAV is used to evaluate prognosis at diagnosis of the vasculitis. The following factors were significantly combined with higher fiveyear mortality: age > 65 years, cardiac involvement, renal insufficiency (creatinine ≥150 μmol/L) and gastrointestinal symptoms. The presence of each was scored +1

<sup>1.</sup> Asthma

<sup>2.</sup> Eosinophilia >10%

<sup>3.</sup> Neuropathy (mono- or poly-neuropathy)

<sup>4.</sup> Non-fixed pulmonary infiltrates

<sup>5.</sup> Paranasal sinus abnormalities

<sup>6.</sup> Extravascular eosinophil infiltration on biopsy

At least four of the six ACR criteria are required.

*Current Treatment of ANCA Vasculitis DOI: http://dx.doi.org/10.5772/intechopen.110375*

Age > 65 years Cardiac insufficiency Renal insufficiency (Creatinemia>150 μmol/L) Gastrointestinal involvement Absence of ear, nose and throat manifestation for GPA and EGPA. One point for each of these five items when present.

#### **Table 3.**

*Revised 2011 Five-Factor score in AAV [21].*

point. Whereas ear, nose and throat (ENT) involvement, affecting patients with GPA and EGPA, were associated with a lower risk of death. Their absence was accorded +1 point (**Table 3**) [21].
