Familial retinoblastoma –a) Has autosomal recessive inheritanceb) More commonly bilateralc) Due to mutationd) More common than sporadic retinoblastomae) Poorer prognosis than sporadic type
**Core Concept**
Familial retinoblastoma is a type of inherited cancer that affects the retina, characterized by a mutation in the RB1 tumor suppressor gene. This genetic defect leads to uncontrolled cell growth and tumor formation in the retina.
**Why the Correct Answer is Right**
Familial retinoblastoma is more commonly bilateral, meaning it affects both eyes, due to the inherited nature of the disease. The mutation in the RB1 gene is present in all cells of the body, increasing the risk of tumor development in both eyes. In contrast, sporadic retinoblastoma, which accounts for the majority of cases, typically affects one eye. The bilateral nature of familial retinoblastoma is a key distinguishing feature.
**Why Each Wrong Option is Incorrect**
* **Option A:** Autosomal dominant inheritance is the correct pattern for familial retinoblastoma, not autosomal recessive. Autosomal recessive inheritance would require two copies of the mutated gene, one from each parent, which is not the case in familial retinoblastoma.
* **Option C:** While the mutation in the RB1 gene is indeed responsible for familial retinoblastoma, stating that it is "due to mutation" is too vague and does not capture the underlying genetic mechanism.
* **Option D:** Familial retinoblastoma is actually less common than sporadic retinoblastoma, which accounts for the majority of cases.
* **Option E:** The prognosis for familial retinoblastoma is generally better than for sporadic retinoblastoma due to earlier detection and treatment.
**Clinical Pearl / High-Yield Fact**
Familial retinoblastoma is a classic example of a hereditary cancer syndrome, highlighting the importance of genetic counseling and screening in families with a history of the disease.
**Correct Answer:** B. More commonly bilateral.