What is MEN2B?

MEN2B is the most aggressive form of MEN2, characterized by medullary thyroid cancer (MTC), pheochromocytomas, and distinctive physical features including mucosal neuromas and marfanoid body habitus. It requires immediate prophylactic thyroidectomy in infancy.

Key Features:

• Medullary Thyroid Cancer (100%): Develops in early childhood; very aggressive
• Pheochromocytomas (50%): Adrenal tumors
• Mucosal Neuromas (100%): Bumpy lips/tongue—pathognomonic
• Marfanoid Habitus: Tall, thin, long limbs (but no lens dislocation or aortic disease like true Marfan)
• GI Issues: Constipation, megacolon from intestinal ganglioneuromatosis

Genetics:

• RET Gene Mutation (M918T most common)
• Autosomal dominant but 50% are de novo mutations
• Highest Risk MEN2 Variant

Diagnosis & Treatment:

• Early Recognition: Physical exam (mucosal neuromas visible in infancy)
• Genetic Testing: Confirms RET mutation
• Prophylactic Thyroidectomy: Within first year of life (preferably before 6-12 months)
• Screen for Pheochromocytomas: Before any surgery (metanephrines, imaging)
• Lifelong Surveillance