Blood test: HIV 1&2= Positive for both mother and child. CD4= 1,639X106/l Radiology: CT brain: a ring-enhancing posterior fossa mass (7x4.5 cm) on the right side with compression of the 4th ventricle causing hydrocephalus Histopathology: Toxoplasmosis. This evidence concerns the gene CD4 and Hydrocephalus.