Native Hydrocephalus vs. Achondroplasia
Left picture: The diagnosis is an acquired hydrocephalus. Right picture: In this girl the macrocephaly is caused by an achondroplasia. This skeletal dysplasia leads to short stature (nanism) and extremities, and to a large head. It is an important differential diagnosis of macrocephaly. In addition to the large head, a combined hydrocephalus may be observed in 25% of achondroplasia cases, needing shunting.
Both girls have a head which is too large. Left picture: This patient is only 5 months old. Notice the slight setting sun sign. Right picture: This female infant is older. The root of the nose is collapsed and the extremities are short.