Ehlers-Danlos syndrome

Ehlers-Danlos syndrome comprises a heterogeneous group of collagen disorders (hereditary connective tissue disease).

Epidemiology

The combined prevalence for all types of Ehlers-Danlos syndrome is estimated to be at least 1 of every 5000 individuals. There is no significant gender predominance.

Clinical presentation

Ehlers-Danlos syndrome clinically manifests with

• skin hyperelasticity and fragility
• joint hypermobility
• blood vessel fragility with bleeding diathesis ¹
• poor tissue healing with delayed healing with tissue paper-like scarring ¹

Subtypes

There are at least ten subtypes with variable inheritance patterns. The majority are autosomal dominant:

• types I and II (also called classic Ehlers-Danlos syndrome) are autosomal dominant and result from mutations in COL5A1 and COL5A2 ⁹.
• type III (also called hypermobility Ehlers-Danlos syndrome) is autosomal dominant with an unknown biochemical origin ⁹.
• type IV (also called vascular Ehlers-Danlos syndrome ⁴) is autosomal dominant and involves the arteries, GI tract, uterus and skin; COL3A1 mutation result in type III collagen production
• type VI (also called kyphoscoliosis Ehlers-Danlos syndrome ⁹) is recessively inherited. It results from a mutation in the gene that encodes lysyl hydroxylase
• type VII is is subclassified into arthrochalasia (type VIIa/b - autosomal dominant) and dermatosparaxis (type VIIc - autosomal recessive) which result from mutations in COL1A1/COL1A2 and procollagen N-peptidase respectively. COL1A1/COL1A2 mutations result in defective conversion of procollagen to collagen ⁹.
• types V, VIII, IX and X are very rare and their features have not been fully described ¹

The 2017 Ehlers-Danlos classification lists 13 subtypes, including several newly-identified rare forms of the disease ^7,8.

Radiographic features

The imaging findings of Ehlers-Danlos syndrome are best discussed according to system.

Soft tissue

• multiple ovoid calcifications (<1 cm) in the subcutaneous tissue
• ectopic ossification ²

Skeletal

• hemarthrosis (especially knees)
• recurrent dislocation: including spontaneous dislocation of the temporomandibular joint ³
• precocious osteoarthritis
• kyphoscoliosis
• spondylolisthesis
• arachnodactyly

Vascular

• fragile blood vessels
• arterial aneurysm formation
• increased occurrence of arterial dissection: aortography contraindicated ²
• dolichoectasia

Thoracic

• diaphragmatic hernia
• emphysema

Gastrointestinal

• ectasias of the gastrointestinal tract