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Ectopia lentis (subluxation of the lens)
👁️ Ectopia Lentis (Lens Subluxation) in Various Conditions
- 🧬 Ehlers-Danlos Syndrome: A connective tissue disorder affecting collagen production. Features include hypermobile joints, stretchy fragile skin, easy bruising, and vascular fragility. Ectopia lentis occurs due to weakened zonular fibers.
- 📏 Marfan's Syndrome: An autosomal dominant disorder affecting fibrillin-1. Classically associated with upward and superotemporal lens dislocation. Other features: tall stature, long limbs, arachnodactyly, high-arched palate, scoliosis, and cardiovascular complications (aortic root dilatation, aneurysm, dissection). Key exam tip: Think "Marfan → Upward lens displacement + Aortic root disease."
- ✋ Weil-Marchesani Syndrome: Rare autosomal recessive condition. Features: short stature, brachydactyly (short stubby fingers), joint stiffness, and microspherophakia (small, spherical lens). Lens subluxation is common and may predispose to glaucoma. Mnemonic: "Weil-Marchesani = short + stiff + small lens."
- 🥬 Refsum's Disease: A peroxisomal disorder caused by impaired phytanic acid metabolism. Features: retinitis pigmentosa, peripheral neuropathy, cerebellar ataxia, deafness, and ichthyosis. Ectopia lentis may occur alongside visual loss from retinal disease.
- 🧩 Homocystinuria: An autosomal recessive metabolic disorder due to cystathionine β-synthase deficiency. Causes accumulation of homocysteine. Lens dislocation is typically downward and inferonasal (vs. upward in Marfan’s). Other features: intellectual disability, osteoporosis, malar flush, fair hair/skin, and high risk of venous/arterial thromboembolism. Exam tip: "Homocystinuria = Downward lens + Clots + Marfan-like skeleton."
- 🧠 Metachromatic Leukodystrophy: A lysosomal storage disorder due to arylsulfatase A deficiency → accumulation of sulfatides. Progressive motor decline, seizures, peripheral neuropathy, and dementia are typical. Ectopia lentis is less common but may be seen with neurological deterioration.
📌 Key Clinical Pearls
- 🔼 Upward dislocation: Marfan’s syndrome.
- 🔽 Downward dislocation: Homocystinuria.
- 👩⚕️ Always assess for systemic features (CV disease in Marfan, thrombosis in Homocystinuria, neuro features in leukodystrophies).
- 🧪 Diagnosis often requires genetic testing, metabolic assays, or enzyme studies depending on the suspected syndrome.