**Core Concept**
Sturge-Weber syndrome is a rare genetic disorder characterized by a port-wine stain, typically on the face, and associated with leptomeningeal angiomatosis, leading to neurological and ocular manifestations.

**Why the Correct Answer is Right**
The presence of a right-sided hemangioma and left-sided focal seizures in a child is highly suggestive of Sturge-Weber syndrome. The port-wine stain is usually present at birth, and the seizures often occur on the contralateral side, due to the involvement of the brain's leptomeningeal vessels. The leptomeningeal angiomatosis leads to cortical atrophy, calcification, and gliosis, resulting in neurological symptoms.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the symptoms described do not match a typical presentation of neurofibromatosis type 1 (NF1), which is characterized by multiple café-au-lait macules, neurofibromas, and Lisch nodules.
* **Option B:** This option is incorrect because the symptoms do not fit a diagnosis of tuberous sclerosis complex (TSC), which typically presents with multiple hamartomas in various organs, including the brain, skin, and kidneys.
* **Option C:** This option is incorrect because the symptoms do not align with a diagnosis of ataxia-telangiectasia, which is characterized by progressive cerebellar ataxia, telangiectasias, and immunodeficiency.

**Clinical Pearl / High-Yield Fact**
Sturge-Weber syndrome is often associated with glaucoma, which can lead to vision loss if not treated promptly. Early detection and management are crucial to preserve vision and prevent further complications.

**Correct Answer:** D.