A 7-year-old child presents with bilateral nasal polyps and recurrent respiratory tract infections. Which genetic condition should be screened for in this clinical scenario?

Explanation

## Bilateral Nasal Polyps in Children: Cystic Fibrosis Screening **Key Point:** Bilateral nasal polyps in a child are a red flag for cystic fibrosis (CF) until proven otherwise. CF is present in 25–50% of children with bilateral nasal polyps. ### Why Cystic Fibrosis Presents with Nasal Polyps 1. **Pathophysiology:** CFTR gene mutation → defective chloride channel → thick, viscous secretions 2. **Sinus involvement:** Chronic sinusitis and polyposis due to impaired mucociliary clearance 3. **Bilateral presentation:** CF polyps are typically bilateral and often occur early in childhood 4. **Associated features:** Recurrent respiratory infections, pancreatic insufficiency, failure to thrive ### Diagnostic Approach ```mermaid flowchart TD A[Child with bilateral nasal polyps]:::outcome --> B{Suspect CF?}:::decision B -->|Yes| C[Sweat chloride test]:::action B -->|No| D[Allergic rhinitis workup] C --> E{Sweat Cl > 60 mEq/L?}:::decision E -->|Yes| F[CF confirmed]:::outcome E -->|No| G[CF excluded]:::outcome E -->|Borderline 30-60| H[Genetic testing CFTR]:::action ``` **High-Yield:** The **sweat chloride test** is the gold standard for CF diagnosis. A value >60 mEq/L is diagnostic; 30–60 mEq/L is borderline and requires genetic confirmation. ### Clinical Pearl **Mnemonic — CF Complications (PANCREAS):** - **P**ancreatic insufficiency - **A**irway obstruction (polyps, bronchiectasis) - **N**asal polyps (25–50% of CF patients) - **C**hronic sinusitis - **R**espiratory infections - **E**ndocrine dysfunction (CF-related diabetes) - **A**bsorption problems (steatorrhea) - **S**alt loss (hyponatremia in heat stress) ### Differential Considerations | Condition | Nasal Polyps | Bilateral | Recurrent RTI | Screening Test | |---|---|---|---|---| | Cystic Fibrosis | Yes (25–50%) | Bilateral | Yes | Sweat Cl test, CFTR gene | | Kartagener (PCD) | Rare | N/A | Yes | Nasal nitric oxide, ciliary biopsy | | Immotile Cilia | Rare | N/A | Yes | Ciliary beat frequency | | Young Syndrome | No | N/A | Yes | Ciliary biopsy | **Warning:** Do not confuse CF with primary ciliary dyskinesia (PCD/Kartagener syndrome). While both cause recurrent infections, nasal polyps are a hallmark of CF, not PCD.