Sturge-Weber syndrome and port-wine stain

What it is

Sturge-Weber syndrome is a congenital, noninherited vascular disorder caused by a somatic mosaic mutation of the GNAQ gene. The mutation leads to abnormal embryonal development of neural crest derivatives, and the result is capillary malformations of the skin, the leptomeninges and the eye. It sits among the neurocutaneous syndromes, a group that exists because the nervous system and the skin have a common ectodermal origin, so an embryological disruption causes syndromes involving abnormalities to both systems. Inheritance is what separates it from the other syndromes in that group: neurofibromatosis and tuberous sclerosis are autosomal dominant, while Sturge-Weber is not inherited and is sporadic, due to a somatic mutation.

How it presents

The sign on the skin is a port-wine stain, also called nevus flammeus: a purple-red patch on the face or neck lying in the distribution of the trigeminal nerve, most often its first and second divisions. A port-wine stain on its own is common and usually not associated with an underlying disorder; approximately 5%-10% lie in the first branch of the trigeminal nerve, the ophthalmic division of the fifth cranial nerve.

When the syndrome is present, the leptomeningeal angioma lies ipsilateral to the stain, and a triad of port-wine stain, glaucoma and homonymous hemianopia is described. What follows from the leptomeningeal vascular malformation is:

• Seizures, on the side contralateral to the angioma, with meningeal and cerebral cortex abnormalities ipsilateral to the stain
• Developmental delay and intellectual disability
• Stroke-like episodes such as hemianopia and hemiparesis, and other focal neurologic deficits

Eye involvement is common and is most often glaucoma, reported in 60% of cases; buphthalmos and a diffuse choroidal hemangioma also occur.