A 2 year old girl is evaluated because of deteriorating vision. On physical examination, a whitish hue is noted in the right pupil, along with strabismus. Palpation of the eye elicits apparent pain and tenderness. The patient is referred to an ophthalmologist, who schedules surgery, and removes a multifocal tumor from the right eye. The pathology repo notes the presence of rosettes composed of cuboidal-to-columnar cells surrounding a central lumen in the tumor. In all likelihood, this child’s condition stems from a mutation in a gene on chromosome ?
A 2 year old girl is evaluated because of deteriorating vision. On physical examination, a whitish hue is noted in the right pupil, along with strabismus. Palpation of the eye elicits apparent pain and tenderness. The patient is referred to an ophthalmologist, who schedules surgery, and removes a multifocal tumor from the right eye. The pathology repo notes the presence of rosettes composed of cuboidal-to-columnar cells surrounding a central lumen in the tumor. In all likelihood, this child’s condition stems from a mutation in a gene on chromosome ?
💡 Explanation
**Core Concept**
The question is testing the student's knowledge of a specific genetic disorder that affects the development of the eye, leading to a multifocal tumor with characteristic histopathological features.
**Why the Correct Answer is Right**
The clinical presentation of deteriorating vision, whitish hue in the pupil, strabismus, and apparent pain and tenderness on palpation of the eye is suggestive of retinoblastoma. This is a malignant tumor of the retina that can occur in early childhood. The presence of rosettes composed of cuboidal-to-columnar cells surrounding a central lumen in the tumor is a characteristic histopathological feature of retinoblastoma. The genetic basis of retinoblastoma is a mutation in the RB1 gene, which is located on chromosome 13q14.
**Why Each Wrong Option is Incorrect**
* **Option A:** Chromosome 3 is not associated with the genetic disorder described in the question.
* **Option B:** Chromosome 11 is not linked to retinoblastoma; it is related to other conditions, such as WAGR syndrome.
* **Option D:** Chromosome 22 is associated with other genetic disorders, such as DiGeorge syndrome, but not with retinoblastoma.
**Clinical Pearl / High-Yield Fact**
Retinoblastoma is a rare but aggressive tumor that can occur in one or both eyes. Early detection and treatment are crucial to prevent metastasis and preserve vision.
**Correct Answer:** C. The RB1 gene mutation on chromosome 13q14 is associated with retinoblastoma.
✓ Correct Answer: D. 13
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