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An autopsy case of small vessel, childhood, primary angiitis of the central nervous system (SVcPACNS): suggestions for establishing specific histologic criteria for diagnosis

SVcPACNS is a rare inflammatory/immune disorder that typically affects the small blood vessels of the brain. SVcPACNS differs from most adult forms of PACNS by being predominantly lymphocytic, non-granulomatous and non-necrotizing. Previously healthy children are typically affected by range of signs and symptoms, including: seizures, headache, cognitive decline, behavior/personality change, focal neurological deficits and potentially a decreased level of consciousness. Treatment protocols featuring induction (steroids and cyclophosphamide) and subsequent maintenance phases (e.g., mycophenolate mofetil) have been demonstrated to yield favorable outcomes. Since SVcPACNS is characteristically angiography negative, the diagnostic gold standard is brain biopsy. Interpretation of these biopsies is often challenging given the histologic overlap between SVcPACNS and encephalitis. Distinguishing the foregoing is critical since the treatment of these entities is significantly different. Herein, a rare autopsy case of SVcPACNS in a 4 year old male is presented. This case provides a unique opportunity to review the Alrawi criteria for the histologic diagnosis of PACNS and establish/refine criteria specific to SVcPACNS. Generally, such criteria should feature: 1) an intramural and lymphocyte predominant infiltrate devoid of multinucleated giant cells; 2) structural vessel alterations lacking fibrinoid necrosis; 3) perivascular pathology supportive of an angiocentric process; 4) the absence of encephalitis; and, 5) the absence of a concurrent systemic or rheumatic illness that could account for the CNS findings.