# Marfan and Ehlers-Danlos Syndromes

> Marfan and Ehlers-Danlos syndromes for NEET-PG Paediatrics covering ectopia lentis, aortic root dilatation and joint hypermobility in Ehlers-Danlos types.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/marfan-and-ehlers-danlos-syndromes
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Nelson Textbook of Pediatrics; Emery and Rimoin's Principles and Practice of Medical Genetics; Ghai Essential Pediatrics
- How to cite: "Marfan and Ehlers-Danlos Syndromes", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/marfan-and-ehlers-danlos-syndromes

## Direct answer

Marfan syndrome is an autosomal dominant connective tissue disorder caused by mutations in FBN1, which encodes fibrillin-1, and it produces ectopia lentis, aortic root dilatation and skeletal overgrowth. Ehlers-Danlos syndromes are a heterogeneous group of inherited collagen disorders defined by skin hyperextensibility, joint hypermobility and tissue fragility. Aortic surveillance with beta-blocker or losartan therapy forms the core of Marfan management, while vascular Ehlers-Danlos carries the gravest risk of arterial rupture.

## What you must remember

- **Marfan genetics:** FBN1 on chromosome 15 encodes fibrillin-1, and many cases arise from new mutations.
- **Ocular clue:** ectopia lentis in Marfan syndrome displaces the lens upward and temporally, whereas homocystinuria displaces it downward and nasally.
- **Skeletal features:** arachnodactyly, an arm span greater than height, pectus deformity, scoliosis and high-arched palate.
- **Cardiovascular risk:** aortic root dilatation with dissection risk, and mitral valve prolapse; beta-blockers or losartan slow dilatation.
- **Hypermobile Ehlers-Danlos:** the commonest type, with no identified gene, so it is diagnosed clinically.
- **Classical Ehlers-Danlos:** COL5A1 or COL5A2 variants, with hyperextensible skin, atrophic scars and joint hypermobility.
- **Vascular Ehlers-Danlos:** COL3A1 variants, thin translucent skin, easy bruising and risk of arterial, bowel or uterine rupture.

## A clinical approach to a tall child with a displaced lens

A 9-year-old is tall with long fingers and a lens displaced upward on slit-lamp examination. The steps below distinguish Marfan syndrome from the Ehlers-Danlos group and set up cardiac surveillance.

1. **Measure the body.** An arm span greater than height, a high-arched palate and long fingers suggest Marfan syndrome, whereas lax skin and widespread joint hypermobility suggest Ehlers-Danlos syndrome.
2. **Examine the eyes.** Upward and temporal ectopia lentis points to Marfan syndrome, and high myopia adds weight to the diagnosis.
3. **Examine the skin.** Hyperextensible skin with atrophic scars suggests classical Ehlers-Danlos, while thin, translucent skin with visible veins suggests the vascular type.
4. **Image the aorta.** Echocardiography measures the aortic root and checks the mitral valve, and it is repeated at intervals to track dilatation.
5. **Test the gene.** FBN1 testing confirms Marfan syndrome, and COL5A1, COL5A2 or COL3A1 testing confirms the classical or vascular types, whereas hypermobile EDS has no identified gene.
6. **Plan protection.** Advise avoidance of contact sports, start a beta-blocker or losartan for dilatation, and plan elective root surgery when the threshold size is reached.

## Where the exam tries to catch you

Three errors recur on this topic.

- **Trap:** a downward and nasal lens displacement attributed to Marfan syndrome — **Correct:** Marfan ectopia lentis is upward and temporal, whereas downward and nasal displacement suggests homocystinuria.
- **Trap:** managing vascular Ehlers-Danlos like Marfan syndrome — **Correct:** the main danger is arterial, bowel or uterine rupture, so elective invasive arterial procedures are avoided.
- **Trap:** treating a negative gene test as proof against hypermobile Ehlers-Danlos — **Correct:** no gene is identified for this type, so the diagnosis rests on clinical criteria.

## Frequently asked questions

### Which gene is mutated in Marfan syndrome?

Marfan syndrome is caused by mutations in FBN1 on chromosome 15, which encodes fibrillin-1, a structural component of microfibrils in connective tissue. Defective microfibrils weaken the aortic wall and the lens zonules. Most cases are autosomal dominant, and many arise from new mutations.

### Why is ectopia lentis useful in separating Marfan syndrome from homocystinuria?

Ectopia lentis helps separate the two because Marfan syndrome displaces the lens upward and temporally, while homocystinuria displaces it downward and nasally. Homocystinuria also causes intellectual disability and thromboembolism. A slit-lamp examination should therefore be part of the assessment of any child with suspected Marfan syndrome.

### Which Ehlers-Danlos type carries the highest risk of arterial rupture?

Vascular Ehlers-Danlos syndrome, caused by COL3A1 variants, carries the highest risk of arterial, intestinal and uterine rupture. Affected people have thin, translucent skin, easy bruising and characteristic facial features. Elective invasive arterial procedures are generally avoided in these patients.

### Why are beta-blockers used in children with Marfan syndrome?

Beta-blockers are used in children with Marfan syndrome to slow aortic root dilatation by reducing the force with which blood strikes the aortic wall. Losartan, an angiotensin receptor blocker, is an alternative option. Regular echocardiographic follow-up then guides when surgical repair of the aortic root is needed.