Tuberous Sclerosis — SCE Dermatology MCQ

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ModeratePaediatric DermatologyTuberous SclerosisSCE Dermatology

A 12-year-old boy presents with multiple hypopigmented macules ('ash leaf spots') on his trunk, facial angiofibromas, and periungual fibromas. MRI brain shows cortical tubers and subependymal nodules. What is the underlying genetic pathway?

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Correct answer: E — mTOR (TSC1/TSC2) pathway

Tuberous sclerosis complex (TSC) is caused by mutations in TSC1 (hamartin) or TSC2 (tuberin) genes, which normally inhibit the mechanistic target of rapamycin (mTOR) pathway. Loss of function leads to constitutive mTOR activation and unregulated cell growth, causing hamartomas in multiple organs (brain, skin, kidneys, heart, lungs). Cutaneous features include ash leaf spots (earliest sign, visible under Wood lamp), facial angiofibromas, shagreen patches, periungual fibromas (Koenen tumours), and confetti-like hypopigmentation. Topical Sirolimus (mTOR inhibitor) is effective for facial angiofibromas.

Reference: BAD 2019; TSC International Consensus 2021