History of the Procedure
Vascular malformations have been recognized throughout history as birthmarks. The cause was thought to be maternal cravings for fruit or maternal dreams, moods, and fantasies. Although Blondel disproved these theories in 1727, some persist today. In 1866, Dugas conducted a scientific analysis of birthmarks and concluded that they were caused by defects in embryologic development. Later, Dupuytren classified vascular malformations as erectile tumors. Virchow and Wagner established the first classification system of vascular malformations, based on channel architecture and histomorphologic appearance. See the images below.
Vascular malformations have been categorized using confusing, inaccurate, and inconsistent terminology. A significant number of patients with vascular lesions receive ineffective and potentially harmful treatment based on misclassification. Mulliken classified vascular malformations using understandable and accurate nomenclature. Vascular malformations are subdivided into low-flow (capillary, venous, lymphatic, or a combination thereof) and high-flow (arterial) anomalies. Clinical, histological, histochemical, and biochemical differences and radiographic imaging findings support this classification.
The prevalence at birth of capillary malformations is reported at 0.3% without predisposition to either sex.
Capillary malformations were once referred to as port-wine stains; this term is now outdated. Genetic studies have mapped capillary malformations to chromosome 5q14-21, showing a defect in the RASA1 gene. The RASA1 gene encodes p120 Ras GTPase-activating protein. When mutated, p120 Ras GTPase-activating protein binds to Krev-1/rap1a, an integrin β1–mediated cell adhesion and angiogenesis protein. The pathogenesis of capillary malformations is not understood.
Capillary malformations are the most common cutaneous vascular malformation appearing as a macular stain. Capillary malformations are represented by ectatic capillaries and medium-sized venules with thin walls and flat endothelial cells. The lack of sympathetic innervation regulating blood flow in vessels with capillary malformation is believed to produce progressive ectasia. Consequently, a characteristic red and purple lesion is seen upon examination.
Unlike hemangiomas, capillary malformations do not undergo spontaneous involution. Further, the endothelium does not exhibit hyper-proliferation but has a normal turnover rate. In a study of 415 patients with capillary malformations in the fifth decade of life, Geronemus and Ashinoff found hypertrophy, nodules, or both in 65% of the capillary vasculature.  In addition to these features, bridged fenestrations can be seen by scanning electron microscopy. These are normally found in venous capillaries surrounding sweat glands and hair follicles and represent areas of accelerated exchange between circulation and surrounding tissue.
Controversy remains as to whether the thickening of postcapillary venules from basement membrane deposition actually occurs.
Patient history and physical examination findings are important in order to correctly classify these malformations. Appropriate treatment begins with the correct diagnosis.
The general consensus is that capillary malformations are located in the dermis. They present as well-defined patches of red or purple skin discoloration at birth but may be masked by erythema of neonatal skin. Their growth correlates closely with the person’s age, becoming increasingly nodular and covering larger areas with time.
Although capillary malformations can occur anywhere on the body, they are most commonly seen on the face. When capillary malformations occur on the face, they normally have a dermatomal distribution. Fifty-five percent of facial capillary malformations overlap sensory dermatomes, occur bilaterally, or cross the mid line. The remaining 45% occur in one of the three trigeminal dermatomes. Maxillary or mandibular overgrowth with labial hypertrophy and gingival hyperplasia may be seen in the lower and mid face.  Soft tissue and skeletal overgrowth may also be seen in cutaneous capillary malformations of the trunk and limbs.
Capillary malformations are commonly associated with developmental defects. For example, a capillary malformation on the posterior chest may be indicative of an underlying arteriovenous malformation (AVM) of the spinal cord (Cobb syndrome), or an occipital capillary malformation may overlie an encephalocele. Spinal dysraphism, lipomeningocele, tethered spinal cord, and diastematomyelia may be present when the capillary malformation overlies the cervical or lumbosacral spine. In these cases, careful neurologic examination, radiographic examination, spinal radiographic imaging, and bladder function studies are indicated because subtle signs of neurogenic bladder dysfunction or lower extremity weakness may be present.
Syndromes involving capillary malformations are discussed below.
Klippel-Trenaunay-Weber syndrome is often associated with the triad of capillary malformations, venous malformations or varicose veins, and hypertrophy of affected tissues. Vascular abnormalities lead to muscle hypertrophy and thickening of the skin, subcutaneous tissues, and bone. Although port-wine stains commonly occur cutaneously, venous and lymphatic malformations are common in the limbs. Most often, they affect a single lower extremity. A persistent lateral vein extending from the lateral malleolus to the gluteal region is common.
Parkes Weber syndrome
Parkes Weber syndrome is the combination of a capillary malformation and an AVM. It is commonly large and pink, with the affected limb being longer and warmer than the contralateral limb.
Hyperkeratotic cutaneous capillary-venous malformation
The hyperkeratotic cutaneous capillary-venous malformation is normally associated with vascular malformation of the brain and affects the tissue around the eye. It is an autosomal dominant abnormality due to a mutation in the KRIT1 gene.
Sturge-Weber syndrome is a capillary malformation in the distribution of the ophthalmic and maxillary divisions of the trigeminal nerve of the face. This vascular malformation may be associated with many other symptoms, such as jacksonian seizures, mental retardation, calcification of the leptomeninges, glaucoma, and contralateral hemiplegia. 
Unlike hemangiomas, capillary malformations display ectatic vessels with flat nonproliferative endothelium. Thickening of the postcapillary venule wall is a common finding. In addition, bridged fenestrations can be seen by electron microscopy.