Which genetic syndrome is most commonly associated with keratoconus?

Explanation

## Genetic Associations with Keratoconus **Key Point:** **Down syndrome (Trisomy 21)** is the **most common genetic syndrome** associated with keratoconus, with a prevalence of 15–20% in Down syndrome patients compared to 0.04–0.6% in the general population. ### Syndromic Associations with Keratoconus | Syndrome | Association Strength | Mechanism | | --- | --- | --- | | **Down syndrome (Trisomy 21)** | **Most common** (15–20% prevalence) | Abnormal collagen synthesis; stromal weakness | | **Ehlers–Danlos syndrome** | Strong (connective tissue disorder) | Defective collagen cross-linking; reduced tensile strength | | **Marfan syndrome** | Moderate | Fibrillin-1 defect; structural weakness | | **Osteogenesis imperfecta** | Moderate | Collagen type I defect | | **Atopic disease** | Strong (non-syndromic) | Chronic eye rubbing; allergic inflammation | | **Turner syndrome** | Rare | Not a primary association | **High-Yield:** The key reason Down syndrome patients develop keratoconus is **abnormal collagen synthesis and stromal weakness**, compounded by the high prevalence of atopic disease (allergies, eczema) in this population, which promotes chronic eye rubbing. **Mnemonic:** **ABCDE of Keratoconus Associations** — **A**topic disease (eye rubbing), **B**iochemical defects (collagen), **C**onnective tissue disorders (Ehlers–Danlos, Marfan), **D**own syndrome, **E**ndocrine disorders (thyroid disease, diabetes). **Clinical Pearl:** Patients with Down syndrome should undergo regular corneal topography screening, especially if they have signs of atopy or frequent eye rubbing, as early detection and interventions (rigid contact lenses, corneal cross-linking) can slow progression.