WBR0782

{{WBRQuestion |QuestionAuthor=Serge Korjian M.D. (Reviewed by Serge Korjian) |ExamType=USMLE Step 1 |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |MainCategory=Pathophysiology |MainCategory=Pathophysiology |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |MainCategory=Pathophysiology |MainCategory=Pathophysiology |SubCategory=Head and Neck, Oncology |Prompt=A 1-week-old boy is brought to the pediatric clinic for a well-baby checkup. The mother reports that her child has been doing well since he has been home. He was born full-term via normal vaginal delivery without any perinatal complications. His first physical exam was unremarkable according to the hospital charts. He has been exclusively breast fed and tolerating several feeds a day. On physical exam, all seems within normal limits, but the pediatrician notices something unusual on eye exam (shown below). Which of the following mutations can explain the findings in this child?

[[Image:WBR0782a.jpg|500px] |Explanation=Leukocoria refers to an abnormal white reflection from the retina where a usual red reflex is expected. Leukocoria in infants raises concern for two important entities: congenital cataracts and retinoblastoma. Retinoblastoma is a rapidly progressing tumor that develops from cells of a retina. It can either be sporadic or inherited. In both cases, the tumor develops due to a mutation in the RB1 gene whose protein product, the retinoblastoma protein, is a tumor suppressor that inhibits G1-to-S transition and regulates the cell cycle. In its inherited form, the mutation of the RB1 gene predisposes to other malignancies later in life. |AnswerA=Elastin gene mutation |AnswerAExp=Elastin mutations are involved in the pathogenesis of Marfan's syndrome. |AnswerB=Retinoblastoma gene mutation |AnswerBExp=Retinoblastoma gene mutations are responsible for development of retinoblastoma which can cause leukocoria. |AnswerC=FGFR3 gene mutation |AnswerCExp=FGFR3 gene mutations are responsible for achodroplasia. |AnswerD=Collagen gene mutation |AnswerDExp=Collagen gene mutations are seen in patients with osteogenesis imperfecta. |AnswerE=p53 gene mutation |AnswerEExp=p53 gene mutations are responsible for the development of several cancers including osteosarcoma, breast and colon cancer. |EducationalObjectives=Leukocoria is an abnormal white reflex that can be seen in children with retinoblastoma. Retinoblastoma occurs due to a mutation in the RB1 gene. |References=Abramson DH, Frank CM, Susman M, Whalen MP, Dunkel IJ, Boyd NW. Presenting signs of retinoblastoma. J Pediatr. 1998;132(3 Pt 1):505-8. |RightAnswer=B |WBRKeyword=Retinoblastoma, Leukocoria, White reflex, Rb, |Approved=Yes }}