A lethal progressive neuroinflammation disguised as MOGAD revealing a final diagnosis of Griscelli syndrome

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is the most frequent cause of first-time optic neuritis in children: a 5-year-old child is presented with an atypical picture of optic neuritis combined with complete right retinal detchment, progressing to a dramatically severe and enigmatic neuroinflammatory picture. Molecular testing panel for hemophagocytic lymphohistiocytosis was performed on peripheral blood mononuclear cells, revealing two RAB27A variants on chromosome 15q21: c.153+5G>A (a splice site variant which alters pre-mRNA splicing) and c.514_518del (a pathogenic 5 bp deletion). RAB27A-related disease is an ultrarare condition called Griscelli syndrome type 2 with features of hemophagocytic lymphohistiocytosis, often fatal.