Immediate Ophthalmology Referral for Retinoblastoma Screening
The most appropriate next step is C - Referral to ophthalmology for urgent retinoblastoma screening, as the brother's diagnosis represents a high-risk hereditary cancer that requires immediate family surveillance regardless of symptoms. 1, 2
Why Ophthalmology Referral is Critical
Children with a sibling diagnosed with retinoblastoma have approximately 45% chance of carrying a germline RB1 pathogenic variant when the affected sibling's disease is hereditary, which justifies heightened surveillance. 1, 2 The American Academy of Ophthalmology and American Academy of Pediatrics recommend that siblings of children with retinoblastoma undergo urgent ophthalmologic evaluation regardless of symptoms, due to the high risk of hereditary disease. 2
- Early detection dramatically improves outcomes and may allow for eye-preserving treatments rather than enucleation. 2
- Hereditary retinoblastoma carries >90% risk of intraocular disease in an autosomal dominant manner, with risks beginning in early infancy. 2
- The ophthalmology referral should be combined with genetic counseling and RB1 testing for both the affected sibling and the at-risk child to clarify carrier status and tailor examination frequency. 1
Why the Other Options Are Inappropriate
CBC (Option A) is Not Indicated
- A complete blood count is not indicated in an asymptomatic child two weeks after an upper respiratory infection when there is no evidence of hematologic disease. 1
- Leukemia surveillance with CBC is only indicated for children with known leukemia predisposition syndromes, not based on family history alone. 2
- The uncle's leukemia does not imply a hereditary cancer syndrome relevant to this child's immediate risk, and the recent URTI is a common viral illness that has resolved. 1
CXR (Option B) is Not Indicated
- A chest X-ray is not indicated in a child whose respiratory infection has resolved and who lacks any respiratory symptoms, fever, or abnormal findings. 1
- Routine imaging for uncomplicated viral upper respiratory infections is explicitly discouraged. 1
- Upper respiratory tract infections are the most common reason for seeking medical care in children and are typically self-limited viral illnesses. 3
BRCA 1&2 Testing (Option D) is Completely Wrong
- BRCA 1/2 testing is not appropriate for evaluating retinoblastoma risk because retinoblastoma is driven by RB1 mutations, not BRCA-associated cancers. 1, 2
- The relevant gene for this family is RB1, not BRCA, and BRCA1/2 mutations are not associated with retinoblastoma or childhood leukemia. 2
Critical Clinical Pitfall to Avoid
Do not delay ophthalmology referral while pursuing unnecessary laboratory or genetic testing. The brother's retinoblastoma diagnosis is the critical red flag that should prompt immediate family screening. 2 Genetic counseling and testing should occur at the time of tumor diagnosis in the family, with siblings evaluated immediately. 2
The recent URTI is a red herring in this clinical scenario—it is a common, self-limited viral illness unrelated to the hereditary cancer risk that requires urgent attention. 3