Ehlers - danlos syndrome

(Edward Ehlers, 1863 - 1937, Danish dermatologist and Henri Alexandre Danlos, 1844 - 1912, French dermatologist), the general name for a group of 11 syndromes involving abnormalities of connective tissue characterized by hyperelasticity and fragility of the skin, hyperlaxity of the joints and a bleeding diathesis. Other systems that may be involved are the eye and the gastrointestinal, bronchopulmonary, genitourinary and cardiovascular systems. These syndromes vary genetically and biochemically but share the same complex of clinical abnormalities. Type IV is the most serious form of the disease and carries a decreased life expectancy.

The primary disorder is a defect in collagen synthesis. No primary bone abnormality has been identified. Molluscoid fibrous tumours composed of proliferating connective tissue and degenerated fat are found predominantly on the pressure points of the body. Patients also exhibit subcutaneous spherules of necrotic fat in the skin that may be related to subclinical trauma. The bleeding diathesis may result from abnormalities in the vessel walls and defects in the supporting perivascular tissues that cause failure of tamponade. Subcutaneous haematomas are also seen.

The joint hypermobility makes it possible for patients to touch the thumb to the forearm, dorsiflex the fifth finger beyond 90⁰, hyperextend the elbow beyond 10⁰, and hyperextend the knee beyond 10⁰ (genu recurvatum). Other abnormalities seen in Ehlers - Danlos syndrome include spontaneous dislocations, ligamentous and capsular laxity resulting in kyphoscoliosis, pes planus deformity and inguinal and hiatal hernia.

Radiographically, multiple subcutaneous dense lesions occurring primarily in the forearms, shins, and extensor surfaces of the extremities resembling phleboliths may be seen owing to calcification of fatty spherules (Fig.1). Calcification may also occur in molluscoid lesions, scars or haematomas, and areas of myositis ossificans.

Persistent joint effusion or haemarthrosis may be noted in patients with Ehlers - Danlos syndrome. The fluid is thought to result from ligamentous and capsular laxity. Repetitive minor stress may lead to widening of the joint spaces. Genu varum may be seen on anteroposterior radiographs of the knee, and lateral knee films can show genu recurvatum. Pectus carinatum, thoracolumbar kyphoscoliosis, spondylolysis and spondylolisthesis may also be observed.

Numerous congenital anomalies are associated with the Ehlers - Danlos syndrome, including arachnodactyly, triphalangeal thumbs, radioulnar synostoses, clubfoot, supernumerary teeth, delayed cranial ossification, micrognathia, elongation of the ulnar styloid process, a short fifth proximal phalanx and posterior radial head dislocations.

DR/RB