Progressive Multifocal Leukoencephalopathy confined to the posterior fossa as the presenting manifestation of HIV in a paediatric patient.

Progressive Multifocal Leukoencephalopathy (PML), primarily affecting immunocompromised individuals due to the John Cunningham virus (JC), is common in HIV-positive adults but rare in paediatrics. We present a unique case of a 14-year-old female with PML as the initial manifestation of HIV, with MRI lesions isolated to the posterior fossa. Initial symptoms included fever and rash, progressing to neurological deficits and ataxia. Severe immune suppression due to HIV and JC virus in the cerebrospinal fluid were confirmed. Management included immune reconstitution therapy (antiretroviral treatment) and supportive care. Despite interventions, the patient had a slow recovery with significant residual neurological sequelae. Timely recognition of Immune Reconstitution Inflammatory Syndrome (IRIS) and steroid initiation proved helpful. Antiretroviral therapy improved the survival rate of HIV-related PML, but long-term neurological sequelae, especially in posterior fossa cases, significantly impact the patient's quality of life. This case highlights diagnostic and treatment challenges in paediatric PML, particularly with atypical lesions location.