Amyloid-β-related angiitis presenting as leptomeningitis.

BACKGROUND

Inflammatory cerebral amyloid angiopathy (ICAA) is an atypical presentation of cerebral amyloid angiopathy (CAA), caused by an autoimmune reaction against cerebral beta-amyloid deposits. ICAA can be divided into two different entities: cerebral amyloid angiopathy-related inflammation (CAA-RI) and amyloid beta-related angiitis (ABRA).

CASE PRESENTATION: We report a histologically confirmed case of ABRA in which initial radiological findings were relatively subtle, resulting in a substantial diagnostic challenge. In this context, supportive cerebrospinal fluid findings, including elevated kappa free light chain index, suggested an inflammatory aetiology with leptomeningitis. A brain biopsy was ultimately required to establish a definitive diagnosis.

CONCLUSIONS

As illustrated in this case, ABRA may present with subtle radiological findings. We highlight the importance of including ABRA in the differential diagnosis of leptomeningitis. We introduce the concept that the kappa index, although currently underused, may represent a biomarker of potential interest and clinical utility in the diagnostic work-up of this group of disorders.