Cutaneous metaplastic synovial cyst in Ehlers-Danlos syndrome.

Classic Ehlers-Danlos syndrome (EDS) is a connective tissue disorder characterized by laxity. The skin, as one of the organs involved, shows hyperextensibility, which makes it prone to trauma. In this context, it would seem logical for cutaneous synovial metaplasia, which is considered a form of repair, to be commonly found in cases of EDS. However, there are only two previously published cases of synovial metaplasia in EDS. We present a third case in a 56-year-old woman with painful redundant skin in both elbows and knees for whom a skin fold of the left elbow was removed to relieve her symptoms. The biopsy showed preservation of the elastic and collagen fibers. The main alteration was the evidence of dermal cystic spaces lined by fibrinoid rests with focal pseudopapillary projections. However, in some zones the cellular lining was preserved, and it was composed of vimentin-positive, fibroblast-like flat, elongated cells, as well as CD68-positive macrophages. No birefringent particles were found in an examination under polarized light.