1. Marfan Syndrome

   • Mutation: FBN1 gene (fibrillin-1)
   • Features: Tall stature, arachnodactyly, lens dislocation, aortic aneurysm/dissection, mitral valve prolapse

2. Neurofibromatosis Type 1 (von Recklinghausen disease)

   • Mutation: NF1 gene (neurofibromin)
   • Features: Cafe-au-lait spots, neurofibromas, Lisch nodules, optic gliomas

3. Neurofibromatosis Type 2

   • Mutation: NF2 gene (merlin/schwannomin)
   • Features: Bilateral vestibular schwannomas, meningiomas, cataracts

4. Huntington Disease

   • Mutation: HTT gene (CAG repeat expansion)
   • Features: Chorea, dementia, psychiatric symptoms, onset usually mid-adult

5. Achondroplasia

   • Mutation: FGFR3 gene
   • Features: Dwarfism with short limbs, large head, normal intelligence

6. Familial Adenomatous Polyposis (FAP)

   • Mutation: APC gene
   • Features: Hundreds to thousands of colon polyps, risk of colon cancer

7. Von Hippel-Lindau Disease

   • Mutation: VHL gene
   • Features: Hemangioblastomas, renal cell carcinoma, pheochromocytomas, pancreatic cysts

8. Multiple Endocrine Neoplasia (MEN) Types 1 and 2

   • MEN 1: MEN1 gene, pituitary, parathyroid, pancreas tumors
   • MEN 2: RET gene, medullary thyroid carcinoma, pheochromocytoma

9. Osteogenesis Imperfecta

   • Mutation: COL1A1/COL1A2 genes
   • Features: Brittle bones, blue sclerae, dental imperfections

10. Tuberous Sclerosis

    • Mutation: TSC1 or TSC2 genes
    • Features: Hamartomas in multiple organs, seizures, ash leaf spots