Skin signs in Ehlers–Danlos syndrome: clinical tests and para-clinical methods

Abstract

Objective: The criteria for Ehlers–Danlos syndrome (EDS) and the hypermobility syndrome (HMS) should be reliable. Examination for general joint hypermobility has high reliability but there is only sparse information on the reliability of skin tests, and no information on the level of normal skin extensibility. The present study aimed to assess skin signs by means of clinical and para-clinical methods.

Methods: A total of 31 EDS patients and 28 healthy controls were examined blinded and in random order. Inter-examiner analysis of clinical tests for skin extensibility, consistency, scarring, and bruising was performed, followed by analyses of extensibility with the suction cup (SC), consistency with a soft tissue stiffness meter (STSM), and thickness with ultrasonography (US). Semi-quantitative assessment of skin extensibility in healthy controls was incorporated in the tests.

Results: The clinical analyses demonstrated kappa values of: 0.72 for extensibility, 0.23 for consistency, 0.53 for scarring, and 0.63 for bruising. Skin extensibility measurements in healthy controls (n = 28) were 2.79 and 2.93 cm (mean + 2 SD), respectively, by the two examiners. There were significant differences between patients with classical-type EDS and controls with respect to skin extensibility by SC (4.91 vs. 12.52 kPa/mm) and skin consistency by STSM (0.59 vs. 0.76 N). We found no difference in skin thickness.

Conclusion: The reproducibility of the clinical skin tests was substantial to good, apart from the consistency measurements. We suggest that skin consistency is withdrawn as a diagnostic criterion. The upper level for normal skin extensibility should be 3 cm. SC and STSM are promising para-clinical methods, but their diagnostic sensitivity and specificity need to be determined.

Acknowledgements

The kind help of clinical geneticist Asger Sørensen in the planning phase is much appreciated, as well as the help of occupational therapist Karen Bjerregaard in making the plaster casts. The Danish Rheumatism Association provided financial support for this study.