**Core Concept**
Tuberous sclerosis complex (TSC) is a genetic disorder characterized by the growth of non-cancerous tumors in various organs, including the brain, skin, and kidneys. This condition is caused by mutations in either the TSC1 or TSC2 gene, leading to the activation of the mammalian target of rapamycin (mTOR) pathway.

**Why the Correct Answer is Right**
The presence of seizures, sub-normal IQ, and multiple oval hypo-pigmented macules on the trunk is highly suggestive of TSC. These macules are known as ash-leaf spots, which are a classic dermatological feature of the condition. The seizures are often due to the formation of subependymal giant cell astrocytomas (SEGAs) in the brain, which can cause hydrocephalus and increased intracranial pressure. The sub-normal IQ is likely due to the developmental impact of the seizures and the presence of cortical tubers.

**Why Each Wrong Option is Incorrect**
**Option A:** Neurofibromatosis type 1 (NF1) is a different genetic disorder characterized by the growth of neurofibromas and café-au-lait macules, rather than oval hypo-pigmented macules.
**Option B:** Sturge-Weber syndrome is a condition characterized by a port-wine stain on the face, seizures, and developmental delay, but it does not typically present with ash-leaf spots.
**Option C:** Hypomelanosis of Ito is a condition characterized by hypopigmentation and seizures, but it does not typically present with the same constellation of symptoms as TSC.
**Option D:** Incontinentia pigmenti is a condition characterized by skin blisters and hyperpigmentation, but it does not typically present with seizures and sub-normal IQ in early childhood.

**Clinical Pearl / High-Yield Fact**
TSC is a multisystem disorder that can affect multiple organs, including the brain, skin, kidneys, and heart. It is essential to consider TSC in the differential diagnosis for children presenting with seizures, developmental delay, and skin lesions.

**Correct Answer:** C.