A patient had probable Coats disease (telangiectatic retinal vessels that subsequently cause retinal detachment and massive exudation). The dermatologic feature of interest was an associated portwine stain in the mandibular and maxillary divisions of the trigeminal nerve. The spectrum of related disorders, including Sturge-Weber syndrome, Lindau disease, racemose vessel disease, and ataxia telangiectasia, is considered.