A 2-year-old is brought for a white pupillary reflex noticed in photographs. Examination shows leukocoria and strabismus. MRI reveals a calcified intraocular mass. Family history notes the father had enucleation of one eye in childhood. If this child carries a germline RB1 mutation, what is the inheritance pattern seen in his offspring?
- A Autosomal dominant with 50 percent transmission ✓
- B Autosomal recessive with 25 percent transmission
- C X-linked recessive affecting sons only
- D Mitochondrial maternal transmission
Correct answer: A. Autosomal dominant with 50 percent transmission
Explanation
Retinoblastoma follows the two-hit model. In heritable cases one mutant RB1 allele at 13q14 is present in every cell, so a single somatic hit triggers tumor, giving apparent autosomal dominant inheritance with 50 percent transmission to offspring. Bilateral or multifocal tumors indicate the germline form, and a parent treated for unilateral retinoblastoma in childhood may still carry the germline mutation. Recessive, X-linked, and mitochondrial patterns do not apply to RB1.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.