Recurrent aseptic meningitis with PIGT mutations: a novel pathogenesis of recurrent meningitis successfully treated by eculizumab.

We report the case of a patient with PIGT mutations who experienced recurrent aseptic meningitis 121 times over 16 years before developing paroxysmal nocturnal haemoglobinuria (PNH). Each episode was preceded by urticaria and arthralgia. After developing PNH, haemolysis occurred prior to meningitis. Flow cytometry revealed deficiency of the glycophosphatidylinositol (GPI)-anchored complement regulatory proteins, CD59 and CD55, and he was diagnosed with PNH. All the symptoms disappeared on administering eculizumab, an anti-C5 antibody. We did not detect mutation in PIGA, which is regarded as the cause of PNH. However, we detected a germ-line mutation and a somatic microdeletion in chromosome 20q including PIGT; PIGT is essential for transferring GPI anchor to the precursors of CD59 and CD55, which play important roles in complement regulation. Loss of these proteins leads to complement overactivation, causing inflammatory symptoms, including recurrent meningitis. PIGT mutations should be considered a novel pathogenesis of recurrent meningitis of unknown aetiology.