====== Primary angiitis of the central nervous system ======
 

Childhood primary [[angiitis]] of the [[central nervous system]] (PACNS) is a rare condition that most often affects small [[vessel]]s (SV), is nearly exclusively lymphocytic and is devoid of a vessel [[necrosis]]. 

===== Diagnosis =====


Diagnosis of Childhood Primary angiitis of the central nervous system is challenging. Gilani and Kleinschmidt-DeMasters noted a possible histological overlap with [[Myelin oligodendrocyte glycoprotein antibody-associated disease]] (MOGAD) on [[biopsy]], prompting a 10-year retrospective review of the experience.

Database search for [[brain biopsy]] cases, age <18 years, performed for an acquired neurological deficit with suspicion of [[vasculitis]], with histological evidence of lymphocytic small-vessel [[inflammation]].

They identified 7 patients; 2/7 were serum-positive for anti-MOG antibodies and 1/7 for anti-NMDA antibodies. The remaining 4/7 proved to be idiopathic lymphocytic vasculitis/cSV-PACNS. All 7 showed overlapping features of lymphocytes permeating parenchymal SV walls, vessel wall distortion without fibrinoid necrosis, and absence of microglial clusters or intravascular thrombi. Tissue infarction was confined to a single case of idiopathic lymphocytic vasculitis. Although demyelination was diligently sought, only subtle demyelination was identified in the 2 MOGAD cases and absent in the remainder.

There is considerable histological overlap between cSV-PACNS and at least some cases of MOGAD or anti-NMDA-[[encephalitis]]; at diagnosis, the differential should include cSV-PACNS but correct [[classification]] requires post-biopsy serological testing
((Gilani A, Kleinschmidt-DeMasters BK. Childhood Small-Vessel Primary Angiitis of the Central Nervous System: Overlap With MOG-Associated Disease. Pediatr Dev Pathol. 2022 Nov 15:10935266221121445. doi: 10.1177/10935266221121445. Epub ahead of print. PMID: 36377607.)).