What is a hallmark feature of Sturge-Weber syndrome?

A hallmark feature of Sturge-Weber syndrome is a port wine stain, which is a type of vascular malformation characterized by a flat, pinkish-red mark on the skin. This stain typically appears on one side of the face, following the distribution of the trigeminal nerve. It can vary in size and intensity but is a distinct physical feature associated with this condition.

Sturge-Weber syndrome is also linked to neurological complications due to the presence of capillary malformations not only in the skin but also in the brain. The port wine stain is crucial for diagnosis and is often accompanied by other symptoms, including seizures and developmental delays. This makes it a defining characteristic of the syndrome that can be observed even in infancy.

In contrast, conditions such as polydactyly, thrombocytopenia, or micropenis are not associated with Sturge-Weber syndrome and would not be expected in its presentation. Each of these other features pertains to different genetic disorders or health issues unrelated to the specific manifestations of Sturge-Weber syndrome.