Facial birthmark, epilepsy and glaucoma in the infant

A 4-week-old infant was initially referred to the dermatology department for review of a birthmark. The lesion was present congenitally and characterised by well-demarcated erythema affecting the bilateral forehead a cheek extending to the philtrum (Fig. 1). Following several episodes of desaturation and poor responsiveness during sleep, he was diagnosed with epilepsy at 5 months of age based on video encephalography. At 6 months of age, glaucoma in his left eye was noted, and a baseline feed and wrap MRI demonstrated changes compatible with leptomeningeal angiomatosis. What is the most likely diagnosis? (Answer on page 389)