Overview of Neurocutaneous Disorders

Apr 10, 2025

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Neurocutaneous Disorders Lecture Notes

Overview

  • Neurocutaneous disorders are genetic diseases affecting the CNS (brain and spinal cord), skin, and bones.
  • Predominantly autosomal dominant inheritance, except for Sturge-Weber syndrome.
  • High yield for USMLE and COMLEX due to overlapping features and unique tumor/skin manifestations.

Neurocutaneous Disorders Discussed

  • Sturge-Weber Syndrome
  • Tuberous Sclerosis
  • Von Hippel-Lindau Disease
  • Neurofibromatosis Type 1 (NF1)
  • Neurofibromatosis Type 2 (NF2)

Sturge-Weber Syndrome

  • Also known as encephalo-trigeminal angiomatosis.
  • Inheritance: Sporadic (non-inherited).
  • Pathophysiology: Somatic mutation of the GNAQ (GNAC) gene.
    • GNAC stabilizes capillary webs.
  • Symptoms:
    • Port wine stain on the face.
    • Leptomeningeal angioma (brain) leading to seizures and intellectual disability.
    • Episcleral hemangioma (eye) leading to early glaucoma.
  • Mnemonic: Think of a "spider web" to remember capillary web issues.

Tuberous Sclerosis

  • Inheritance: Autosomal dominant.
  • Pathophysiology: Mutations in TSC1 (chromosome 9) and TSC2 (chromosome 16).
    • TSC1 codes for hamartin; TSC2 for tuberin.
  • Symptoms:
    • Ash leaf spots.
    • Cardiac rhabdomyoma.
    • Renal angiomyolipoma.
    • Chagrin patch.
    • Ungual fibromas.
    • Adenoma sebaceum (resembles acne but is actually fibromas).
  • Mnemonic: "Myo = Muscle = Tuba = Tuberous Sclerosis" (muscle-related tumors like rhabdomyoma, angiomyolipoma).

Von Hippel-Lindau Disease

  • Inheritance: Autosomal dominant.
  • Pathophysiology: Deletion of VHL gene on chromosome 3.
    • Normally inhibits protein degradation.
  • Symptoms:
    • Bilateral renal cell carcinoma.
    • Pheochromocytoma.
    • Hemangioblastomas.
    • Angiomas.
  • Mnemonic: "HARP" (Hippo playing the harp):
    • Hemangioma
    • Angioblastoma
    • Renal cell carcinoma (bilateral)
    • Pheochromocytoma

Neurofibromatosis Type 1 (NF1)

  • Inheritance: Autosomal dominant.
  • Pathophysiology: Alteration of NF1 gene on chromosome 17.
    • Codes for neurofibromin, a tumor suppressor protein.
  • Symptoms:
    • Café au lait spots.
    • Multiple cutaneous neurofibromas.
    • Optic gliomas.
    • Lisch nodules (pigmented iris hamartomas).
  • Mnemonic: "I'll have the number one, please" for café au lait spots (coffee shop reference).

Neurofibromatosis Type 2 (NF2)

  • Inheritance: Autosomal dominant.
  • Pathophysiology: NF2 gene on chromosome 22.
    • Codes for merlin/schwannomen, a tumor suppressor.
  • Symptoms:
    • Bilateral acoustic schwannomas (affecting cranial nerves 5, 7, 8).
    • Ependymomas, meningiomas.
    • Juvenile cataracts.
  • Mnemonic: "Twos" - bilateral features and chromosome 22.

Summary

  • Sturge-Weber: Port wine stain, leptomeningeal angioma, episcleral hemangioma; capillary issues.
  • Tuberous Sclerosis: Ash leaf spots, cardiac rhabdomyoma, renal angiomyolipoma; myo=muscle=tuba.
  • Von Hippel-Lindau: HARP mnemonic; hemangioma, angioblastoma, bilateral renal cell carcinoma, pheochromocytoma.
  • NF1: Café au lait spots, cutaneous neurofibromas, Lisch nodules, optic glioma.
  • NF2: Bilateral acoustic schwannomas; affects cranial nerves 5, 7, 8. Involves "twos".

Revising these mnemonics and pathophysiology can aid significantly in mastering these neurocutaneous disorders for medical exams.