Periosteal new bone formation in Klippel-Trénaunay syndrome: a case report.

Background: Klippel-Trénaunay syndrome (KTS) is a complex congenital vascular disorder, typically accompanied by port-wine stains, varicose veins, and limb hypertrophy. This paper reports a rare and unusual clinical condition of periosteal reaction in a pediatric case of KTS. Although periosteal new bone formation is not rare in children, as is KTS, their dual occurrence or the presentation of the former due to KTS has not been previously documented. Our objective in this study is to highlight the potential association between periosteal new bone formation and KTS, as well as to help physicians consider this association when bone neoplasm has been ruled out.

Case Presentation: A 7-year old girl, initially presented with a persistent mild swelling in her left shank, with no abnormalities in the X-ray of the tibiofibular. However, after a few consults and examinations, 7 weeks later, a 17 cm-long periosteal new bone formation along the left tibia and diffused dilated vessels in the left shank were revealed by the radiological examination. Not knowing the true nature of the fast-growing lesion in a typical case of KTS was worrying. Therefore, a core needle biopsy was performed. The test demonstrated a possible parosteal hemangioma. Following further investigation through an excisional biopsy, and a pathological analysis, hyperplasia of the bone tissues with no tumor cells was revealed. Thereafter, an elastic stocking treatment was prescribed. During the first two-year follow-up, recurrence of the mass or sign of progression of KTS was not observed.

Conclusions: Periosteal new bone formation is a potential manifestation of KTS. Based on the conclusive pathological results of the excisional biopsy, invasive examinations and surgeries could be avoided in future KTS-subperiosteal lesion manifestations.