Page 173 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

Classification of Pediatric Vasculitides 149

Other defining features were skin biopsy features of necrotizing non-granulomatous
vasculitis and evidence of prior streptococcal infection, without ANCA-seropositivity [22].

Anti-Neutrophil Cytoplasm Antibody-Associated Vasculitis

Microscopic Polyangiitis
MPA is a pauci-immune necrotizing small vessel vasculitis and necrotizing

glomerulonephritis occurs in most affected patients. Both the Revised 2012 CHCC and the
EULAR/PRES census criteria reflect the presence of MPO-ANCA positivity [22].

Granulomatosis with Polyangiitis
GPA is a necrotizing AAV that affects small- to medium-sized vessels [38]. Although

rare in childhood with an estimated incidence of 0.24 per 100,000 children annually, cGPA is
the commonest diagnosed pediatric AAV [39]. The ACR classification of GPA required two
of the following four features including, nasal-oral inflammation, abnormal chest X ray,
abnormal urinalysis, and granulomatous inflammation on biopsy [21]. Approximately 90% of
cGPA patients are ANCA-seropositive [40] thus, ANCA-seropositivity was added as a new
criterion. Most features of GPA are similar in children and adults. However, subglottic
stenosis has been reported to be more common in cGPA [41, 42]. Based on these data, the
presence of subglottic, tracheal, or endobronchial stenosis was added to the group of criteria
for cGPA [24]. Another minor modification was the addition of chest computed tomography
(CT) scanning results to the definitions based on radiological imaging [24].

According to the final form of the criteria, cGPA classification required at least three of
the following six features including, granulomatous inflammation on biopsy, upper airway
involvement, laryngo-trachea-bronchial stenosis, pulmonary involvement on a chest
radiograph or CT, ANCA-seropositivity, and renal involvement [24]. The resulting criteria
achieved a sensitivity of 93.3% and a specificity of 89.2% [24].

Large Vessel Vasculitis

Takayasu Arteritis

TAK is a granulomatous large vessel vasculitis involving the aorta and its main branches
leading to stenosis and aneurysms [38]. The mean prevalence of TAK was 4.7 per million
adults [43] however; pediatric incidence data for TAK are not readily available. It is
predominantly a disease of the third decade, but can occur in children as well [44]. In fact,
20% of all TAK patients are younger than 19 years of age at disease onset [45] and it has
been suggested that onset at age younger than 15 years was associated with a probability of
delay in diagnosis [46]. Thus, it is important for pediatricians to recognize cTAK. The ACR
criteria for cTAK require the presence of three of the following six criteria including, age less
than 40 years, claudication of the extremities, decreased brachial pulse, blood pressure
difference >10 mmHg between arms, bruit over subclavian arteries or aorta, and
arteriographic abnormalities [19]. During the process of revising these criteria, the age

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