Although Klippel-Trénaunay syndrome is a rare congenital (present at birth) disorder, it is the most common condition involving combined vascular malformations. The syndrome is characterized by a localized or diffuse capillary malformation (portwine stain) that overlies a venous malformation and/or lymphatic malformation with associated soft tissue and bone hypertrophy (excessive growth). The portwine stain is typically substantial, varicose veins are often quite numerous, and bone and soft tissue hypertrophy is variable. The affected limb is either larger or smaller than the unaffected limb. Hypertrophy occurs most commonly in the lower limbs, but may affect the arms, the face, the head or internal organs. Additionally, a wide range of other skeletal and skin abnormalities sometimes coexists (illustration 1). Patients may have an increased extremity circumference and an increase or decrease in the length of the limb.
Bony enlargement is usually not present at birth, but may appear within the first few months or years of life and may become particularly problematic during puberty. The affected area grows longer and thicker due to increased blood supply. Sometime after puberty and before age 30,small vesicles (lymphatic blebs) appear within the capillary lesion.
In some patients, small lymphatic vesicles may appear. These vesicles may leak clear or blood-tinged fluid.
In young adults, the capillary malformation may thicken and become more prominent.