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Klippel-Trenaunay syndrome (Klippel-Trenaunay-Weber syndrome; angio-osteohypertrophy syndrome) is a developmental vascular abnormality of the extremities. Classically, there is the triad of cutaneous capillary malformations, dilated superficial veins or venous malformations, and overgrowth of the limb (local gigantism). Capillary-lymphaticovenous malformations are present in the deeper soft tissues in most of these patients as well. Typically, the abnormality involves a single lower extremity (95%); arm involvement is rare. Klippel-Trenaunay syndrome apparently is due to a disturbance in embryogenesis, with persistence of primitive arteriovenous communications within the developing limb bud. Abnormalities of superficial veins in these patients range from ectasia of small veins to large venous or lymphaticovenous malformations. Potential deep venous abnormalities include aplasia, hypoplasia, aneurysmal dilation, duplications, and valvular incompetence.1–3

Klippel-Trenaunay syndrome has no gender or racial predilection. Most cases are sporadic. The clinical findings of Klippel-Trenaunay syndrome include superficial varices, port wine telangiectatic nevi, and hypertrophy of the soft tissues and bones of the extremity. The port wine skin lesions are usually evident early in infancy. Progressive dilation of superficial veins usually begins with ambulation. Various complications can eventually develop due to the abnormal venous and lymphatic drainage, including thrombophlebitis, edema, and ulcerations. Cutaneous vascular malformations may extend beyond the limb, but usually do not cross the midline. Visceral vascular malformations of the colon and urinary bladder occur in occasional patients. Extremity hypertrophy is the most variable of the 3 classic features of Klippel-Trenaunay syndrome. There may be osseous lengthening, soft tissue hypertrophy, or both. Other potential clinical manifestations include protein-losing enteropathy, thrombocytopenia (due to platelet sequestration), hematuria, hematochezia, systemic hypertension, and renal failure. Patients with Klippel-Trenaunay syndrome occasionally have ipsilateral cerebral hemihypertrophy.

Imaging studies of patients with Klippel-Trenaunay syndrome demonstrate osseous and soft tissue overgrowth in the affected extremity (Figure 64-1). The bones are elongated and widened, and there is a variable degree of cortical thickening. Phleboliths may be visible radiographically in venous malformations within the affected extremity or throughout the body. Venography of patients with Klippel-Trenaunay syndrome usually shows small size or absence of some or all of the major deep veins of the involved extremity. However, there is considerable variability in the deep venous anatomy in these patients. There are multiple dilated, tortuous, valveless superficial veins. Abnormal venous channels may extend between deep veins and the dilated superficial veins. Arteriography shows a normal arterial phase (or slight enlargement of the ipsilateral arteries), an irregular blush during the tissue phase, and dilated superficial veins on delayed images. The anomalous venous anatomy can also be evaluated with sonography, contrast-enhanced CT, MR, or contrast-enhanced MR angiography (Figure 64-2).4,5

Figure 64–1

Klippel-Trenaunay syndrome.

An orthoroentgenogram of a 15-year-old girl shows elongation and enlargement of the long bones of the right leg. There is marked prominence of the soft tissues of the right leg, due to vascular malformations.

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