The question of whether hypermobility in children is a benign condition or part of an underlying connective tissue disorder can be a challenging one.
Children have more hypermobile joints than adults, and their skin can be soft and pliable. These are both features of a group of 13 connective tissue disorders known as Ehlers-Danlos syndromes (EDS).
EDS recently were reclassified according to their predominant features and underlying etiologies, with the exception of hypermobile EDS (hEDS), the underlying etiology of which is unknown. The new criteria for hEDS place a higher threshold for joint hypermobility (using the Beighton scoring system) for prepubertal children and adolescents than for pubertal men and women up to age 50. In addition, other criteria must be met to make the diagnosis of hEDS.
When to suspect connective tissue disorder
The hypermobile form of Ehlers-Danlos syndrome, the most common EDS, is a clinical diagnosis based on three criteria: 1) generalized joint hypermobility; 2) a constellation of musculoskeletal complications, systemic manifestations and positive family history; and 3) exclusion of other possible disorders.
Hypermobility also is a feature of the other EDS types as well as other connective tissue disorders. The presence of the following signs and symptoms may be a reason to refer a patient for a formal evaluation for a connective tissue disorder. Such referrals could be to clinical genetics, rheumatology, cardiology or orthopedics depending on the features and symptoms.
- Generalized joint hypermobility: This is assessed using the Beighton scoring system, which tests for hypermobility of the fingers, wrists, elbows, knees and spine. For prepubertal children, a score of 6 or more out of 9 is considered hypermobile. Children with joint hypermobility may be asymptomatic, and a referral for a possible connective tissue disorder depends on other associated features and/or a family history.
- Joint dislocations/joint subluxations: Congenital hip dislocations are not uncommon. They may be isolated, a result of breech presentation or could indicate an underlying connective tissue disorder. Children with recurrent dislocations/subluxations especially in combination with joint hypermobility could have an underlying connective tissue disorder.
- Skin: Hyperextensible skin (particularly if the skin can be stretched more than 3 centimeters at the neck), soft, velvety skin, poor wound healing, thin skin and prominent veins can be seen in EDS. Children can have very soft, hyperextensible skin especially during infancy. Bruising beyond what is expected, atrophic scars and easily visible veins could be clues to an underlying connective tissue disorder. However, scars can be wide depending on the location and treatment.
- Hypotonia: Congenital muscle hypotonia can be due to many causes. However, hypotonia in combination with joint or skin findings can be seen in various connective tissue disorders.
- Kyphoscoliosis: Progressive scoliosis or kyphoscoliosis especially at a young age without structural vertebral anomalies can be seen in some forms of EDS and warrants evaluation.
- Ophthalmologic: Various eye abnormalities can be seen in EDS as well as other connective tissue disorders. Blue or grayish sclerae (beyond infancy) may indicate thin sclerae and connective tissue involvement (beyond osteogenesis imperfecta).
- Cardiac: Mitral valve prolapse and aortic root dilation can be seen in EDS and should also prompt an evaluation for a connective tissue disorder.
- Family history: Positive family history of a connective tissue disorder should raise the possibility of a connective tissue disorder in a child given that many of these conditions are autosomal dominant. In fact, the criteria for hEDS include a first-degree relative diagnosed with hEDS using the new criteria. Similarly, a family history of aneurysms or rupture of arteries or organs, especially at young ages, raises the possibility of vascular EDS.