[Anti-MOG antibody spectrum disease with annular-enhancing brain lesions in an immunocompetent child].

We report a rare diagnosis of ring-enhanced brain lesions. We describe a case of a 4-year-old immunocompetent girl presenting with a subacute alteration of her general condition and a walking disorder a few weeks after her return from a trip to Bangladesh. The etiological work-up revealed ring-enhanced brain lesions on magnetic resonance imaging (MRI). A wide range of etiologies, including infectious, tumoral and inflammatory causes, were considered. Given the clinical and radiological suspicion of neurocysticerosis, the patient was initially treated with corticosteroids and various infectious serologies were carried out, with negative results. Following a rapidly favourable clinical course on corticosteroids alone, further biological investigations revealed the presence of anti-MOG antibodies in both serum and cerebrospinal fluid, suggesting MOGAD (myelin oligodendrocyte glycoprotein antibody-associated disease). This case report highlights the complexity of diagnosing ring-enhanced brain lesions. It also draws attention to MOGAD in immunocompetent patients as a rare but possible etiology, to be systematically investigated in the presence of this type of lesion. Indeed, consideration of inflammatory and autoimmune causes is crucial for accurate diagnosis, enabling earlier targeted treatment.