Primary angiitis of the central nervous system presenting as a mass lesion

• Primary angiitis of the central nervous system is an uncommon condition.
• It causes inflammation of the blood vessels of the central nervous system.
• Accurate diagnosis is challenging due to the absence of specific serological tests.
• This case presents atypically as a mass lesion highlighting the difficult diagnosis.

We report a 51-year-old Asian man with primary angiitis of the central nervous system (PACNS) with atypical presentation as a mass lesion. PACNS is an uncommon condition causing inflammation and destruction of the blood vessels of the central nervous system. The aetiology is unclear and multiple mechanisms have been proposed. Its incidence is estimated at 2.4 per million per year, affecting patients of all ages (median 50 years) and more commonly Caucasian men. In Australia, 12 patients fulfilled the diagnostic criteria for PACNS between 1998 and 2009 at The Royal Melbourne Hospital, a university-affiliated tertiary referral centre. The accurate and timely diagnosis of PACNS is very challenging due to disease mimicry and the absence of specific serological tests. This patient illustrates additional diagnostic difficulty with his atypical PACNS presentation as a mass lesion.