Combined capillary-venous-lymphatic malformations without overgrowth in patients with Klippel-Trénaunay syndrome

Objective: Klippel-Trénaunay syndrome (KTS) is described in the literature as a complex syndrome characterized by various combinations of capillary, venous, and lymphatic malformations associated with limb overgrowth. In the first description by Maurice Klippel and Paul Trénaunay, tridimensional bone hypertrophy was believed to be the cause of limb enlargement. The purpose of this study was primarily to assess the presence of real bone hypertrophy as a cause of enlargement of the limb and to underline the rare presence of undergrowth of the affected limb in patients with KTS. Methods: A two-center retrospective review including 17 KTS patients with various combinations of capillary, venous, and lymphatic malformation affecting the lower limb was performed. Differences in limb dimension were evaluated clinically. Width and length discrepancy of the affected limb was measured with radiologic imaging. Results: We found an increase of length in the affected limb in 80% of the patients. The leg length discrepancy varied from 0.2 to 2.6 cm. The median leg length discrepancy was found to be 1.4 cm. Three patients had a reduced length of the affected limb. Girth enlargement of the affected extremity was noticed in 60% of the patients, and 2 of 17 patients had hypotrophy of the involved limb. Hypertrophy (an increase in both length and width) of the bone was found in none of our cases, and the circumferential enlargement of the affected extremity was related only to soft tissue enlargement. Conclusions: In the literature, KTS is considered the prototype of overgrowth syndromes associated with complex vascular malformations. The majority of our patients showed limb length increase associated with soft tissue enlargement without an increase of bone width; there were also two patients with limb undergrowth. A real bone overgrowth (an increase in both length and width) was not present in our patients. Therefore, we could consider the absence of real bone hypertrophy as probably a new aspect of such confusing and controversial definitions of KTS. In addition, it would be more accurate to classify KTS patients on the basis of their phenotypic features (type of vascular malformation, types of overgrown tissue) rather than by use of an outdated eponym.