Usually observed at birth or shortly thereafter in 94% of patients, in other reports, patients did not develop skin lesions until 3 months or even 2 years after birth. Females are typically affected more often than males (64%).

The prognosis is favorable in most patients with an isolated cutaneous abnormality. In the majority of cases, both the vivid red marking and the difference in circumference of the extremities regress spontaneously during the first year of life. It is theorized that this may be due to the normal maturation process, with thickening of the epidermis and dermis. Improvements for some patients can continue for up to 10 years, while in other cases, the marbled skin may persist for the patient's lifetime.

One study reported an improvement in lesions in 46% of patients within 3 years. If CMTC persists into adulthood, it can result in complaints due to paresthesia, increased sensitivity to cold and pain, and the formation of ulcers.

Few reports included long-term follow up of CMTC into adolescence and adulthood. While about 50% of patients seem to show definite improvement in the reticular vascular pattern, the exact incidence and cause of persistent cases are unknown.

Population studies from numerous areas in the world have shown that HHT occurs at roughly the same rate in almost all populations: somewhere around 1 in 5000. In some areas, it is much more common; for instance, in the French region of Haut Jura the rate is 1:2351 - twice as common as in other populations. This has been attributed to a founder effect, in which a population descending from a small number of ancestors has a high rate of a particular genetic trait because one of these ancestors harbored this trait. In Haut Jura, this has been shown to be the result of a particular "ACVRL1" mutation (named c.1112dupG or c.1112_1113insG). The highest rate of HHT is 1:1331, reported in Bonaire and Curaçao, two islands in the Caribbean belonging to the Netherlands Antilles.

Most people with HHT have a normal lifespan. The skin lesions and nosebleeds tend to develop during childhood. AVMs are probably present from birth, but don't necessarily cause any symptoms. Frequent nosebleeds are the most common symptom and can significantly affect quality of life.

The causes for PWS are either genetic or unknown. Some cases are a direct result of the RASA1 gene mutations. And individuals with RASA1 can be identified because this genetic mutation always causes multiple capillary malformations. PWS displays an autosomal dominant pattern of inheritance. This means that one copy of the damaged or altered gene is sufficient to elicit PWS disorder. In most cases, PWS can occur in people that have no family history of the condition. In such cases the mutation is sporadic. And for patients with PWS with the absence of multiple capillary mutations, the causes are unknown.

According to Boston’s Children Hospital, no known food, medications or drugs can cause PWS during pregnancy. PWS is not transmitted from person to person. But it can run in families and can be inherited. PWS effects both males and females equally and as of now no racial predominance is found

At the moment, there are no known measures that can be taken in order to prevent the onset of the disorder. But Genetic Testing Registry can be great resource for patients with PWS as it provides information of possible genetic tests that could be done to see if the patient has the necessary mutations. If PWS is sporadic or does not have RASA1 mutation then genetic testing will not work and there is not a way to prevent the onset of PWS.

A number of conditions may cause the appearance of livedo reticularis:

- Cutis marmorata telangiectatica congenita, a rare congenital condition

- Sneddon syndrome – association of livedoid vasculitis and systemic vascular disorders, such as strokes, due to underlying genetic cause

- Idiopathic livedo reticularis – the most common form of livedo reticularis, completely benign condition of unknown cause affecting mostly young women during the winter: It is a lacy purple appearance of skin in extremities due to sluggish venous blood flow. It may be mild, but ulceration may occur later in the summer.

- Secondary livedo reticularis:

- Vasculitis autoimmune conditions:

- Livedoid vasculitis – with painful ulceration occurring in the lower legs

- Polyarteritis nodosa

- Systemic lupus erythematosus

- Dermatomyositis

- Rheumatoid arthritis

- Lymphoma

- Pancreatitis

- Chronic pancreatitis

- Tuberculosis

- Drug-related:

- Adderall (side effect)

- Amantadine (side effect)

- Bromocriptine (side effect)

- Beta IFN treatment, "i.e." in multiple sclerosis

- Livedo reticularis associated with rasagiline

- Methylphenidate and dextroamphetamine-induced peripheral vasculopathy

- Gefitinib

- Obstruction of capillaries:

- Cryoglobulinaemia – proteins in the blood that clump together in cold conditions

- Antiphospholipid syndrome due to small blood clots

- Hypercalcaemia (raised blood calcium levels which may be deposited in the capillaries)

- Haematological disorders of polycythaemia rubra vera or thrombocytosis (excessive red cells or platelets)

- Infections (syphilis, tuberculosis, Lyme disease)

- Associated with acute renal failure due to cholesterol emboli status after cardiac catheterization

- Arteriosclerosis (cholesterol emboli) and homocystinuria (due to Chromosome 21 autosomal recessive Cystathionine beta synthase deficiency)

- Intra-arterial injection (especially in drug addicts)

- Ehlers-Danlos syndrome – connective tissue disorder, often with many secondary conditions, may be present in all types

- Pheochromocytoma

- Livedoid vasculopathy and its association with factor V Leiden mutation

- FILS syndrome (polymerase ε1 mutation in a human syndrome with facial dysmorphism, immunodeficiency, livedo, and short stature)

- Primary hyperoxaluria, oxalosis (oxalate vasculopathy)

- Cytomegalovirus infection (very rare clinical form, presenting with persistent fever and livedo reticularis on the extremities and cutaneous necrotizing vasculitis of the toes)

- Generalized livedo reticularis induced by silicone implants for soft tissue augmentation

- As a rare skin finding in children with Down syndrome

- Idiopathic livedo reticularis with polyclonal IgM hypergammopathy

- CO angiography (rare, reported case)

- A less common skin lesion of Churg-Strauss syndrome

- Erythema nodosum-like cutaneous lesions of sarcoidosis showing livedoid changes in a patient with sarcoidosis and Sjögren's syndrome

- Livedo vasculopathy associated with IgM antiphosphatidylserine-prothrombin complex antibody

- Livedo vasculopathy associated with plasminogen activator inhibitor-1 promoter homozygosity and prothrombin G20210A heterozygosity

- As a first sign of metastatic breast carcinoma (very rare)

- Livedo reticularis associated with renal cell carcinoma (rare)

- Buerger's disease (as an initial symptom)

- As a rare manifestation of Graves hyperthyroidism

- Associated with pernicious anaemia

- Moyamoya disease (a rare, chronic cerebrovascular occlusive disease of unknown cause, characterized by progressive stenosis of the arteries of the circle of Willis leading to an abnormal capillary network and resultant ischemic strokes or cerebral hemorrhages)

- Associated with the use of a midline catheter

- Familial primary cryofibrinogenemia.

The overall prognosis is excellent in most cases. Most children with Adams–Oliver syndrome can likely expect to have a normal life span. However, individuals with more severe scalp and cranial defects may experience complications such as hemorrhage and meningitis, leading to long-term disability.

This condition has been linked to mutations in the ribosomal GTPase BMS1 gene.

Sack–Barabas syndrome is rare and has an estimated prevalence of 1 in 100,000 to 200,000.

The initial clinical manifestation of vascular problems in patients with SBS is early, about 25% have their first symptoms at age 20 and more than 80% of patients have had at least one complication by the age of 40.

The median survival for one study of SBS patients was only 48 years.

Other than identifying and treating any underlying conditions in secondary livedo, idiopathic livedo reticularis may improve with warming the area.

Several anti-angiogenesis drugs approved for other conditions, such as cancer, have been investigated in small clinical trials. The anti-VEGF antibody bevacizumab, for instance, has been used off-label in several studies. In the largest study conducted so far, bevacizumab infusion was associated with a decrease in cardiac output and reduced duration and number of episodes of epistaxis in treated HHT patients. Thalidomide, another anti-angiogenesis drug, was also reported to have beneficial effects in HHT patients. Thalidomide treatment was found to induce vessel maturation in an experimental mouse model of HHT and to reduce the severity and frequency of nosebleeds in the majority of a small group of HHT patients. The blood hemoglobin levels of these treated patients rose as a result of reduced hemorrhage and enhanced blood vessel stabilization.

Children with DOCK8 deficiency do not tend to live long; sepsis is a common cause of death at a young age. CNS and vascular complications are other common causes of death.

The disease is inherited by autosomal dominant transmission with complete penetrance but variable expression. This means that children of an affected parent that carries the gene have a 50% chance of developing the disorder, although the extent to which they are affected is variable.

Bart syndrome is caused by ultrastructural abnormalities in the anchoring fibrils. Genetic linkage of the inheritance of the disease points to the region of chromosome 3 near the collagen, type VII, alpha 1 gene (COL7A1).

Aplasia cutis congenita (ACC) is a rare disorder characterized by congenital absence of skin. Frieden classified ACC in 1986 into 9 groups on the basis of location of the lesions and associated congenital anomalies. The scalp is the most commonly involved area with lesser involvement of trunk and extremities. Frieden classified ACC with fetus papyraceus as type 5. This type presents as truncal ACC with symmetrical absence of skin in stellate or butterfly pattern with or without involvement of proximal limbs.]It is the most common congenital cicatricial alopecia, and is a congenital focal absence of epidermis with or without evidence of other layers of the skin.

The exact etiology of ACC is still unclear but intrauterine infection by varicella or herpes virus, drugs such as methimazole, misoprostol, valproate, cocaine, marijuana etc., fetus papyraceus, feto-fetal transfusion, vascular coagulation defects, amniotic membrane adherence, abnormal elastic fiber biomechanical forces and trauma are implicated. It can be associated with Johanson-Blizzard syndrome, Adams-Oliver syndrome, trisomy 13, and Wolf-Hirschhorn syndrome.

It can also seen with exposure to methimazole and carbimazole in utero. This dermatological manifestation has been linked to Peptidase D haploinsufficiency and a deletion in Chromosome 19.

Focal dermal hypoplasia has been associated with PORCN gene mutations on the X chromosome. 90% of the individuals who are affected with the syndrome are female: the commonly accepted, though unconfirmed, explanation for this is that the non-mosaic hemizygous males are not viable.

The differential diagnosis of focal dermal hypoplasia (Goltz) syndrome includes autosomal recessive Setleis syndrome due to TWIST2 gene mutations. It associated with morning glory anomaly, polymicrogyria, incontinentia pigmenti, oculocerebrocutaneous syndrome, Rothmund-Thomson syndrome and microphthalmia with linear skin defects (also known as MLS) syndrome because they are all caused by deletions or point mutations in the HCCS gene.

Autosomal dominant porencephaly type I is rare and its prevalence and incidence are unknown. It affects males and females equally.

AOS is a rare genetic disorder and the annual incidence or overall prevalence of AOS is unknown. Approximately 100 individuals with this disorder have been reported in the medical literature.

Treatment is symptomatic, often addressing indicators associated with peripheral pulmonary artery stenosis. Laryngotracheal calcification resulting in dyspnea and forceful breathing can be treated with bronchodilators including the short and long-acting β2-agonists, and various anticholinergics. Prognosis is good, yet life expectancy depends on the severity and extent of diffuse pulmonary and arterial calcification.

Frequencies of this disease are the greatest in Norway with a few Finnish cases have also having been noted to date. Some cases have been found in other ethnicities such as in people of Indian or Japanese descent as well as a north Italian family. These cases are scattered and there are potentially more under reported cases as this disease is often under diagnosed for other cutaneous diseases. It is most prevalent in a defined region in the middle of Norway and Sweden with a heterozygote carrier frequency of 1 in 50.

Bart syndrome is a genetic disorder characterized by the association of congenital localized absence of skin, epidermolysis bullosa, lesions of the mouth mucosa, and dystrophic nails.

DOCK8 deficiency is very rare, estimated to be found in less than one person per million; there have been 32 patients diagnosed as of 2012.

Kaposiform hemangioendothelioma (KHE) is a rare vascular neoplasm that is locally aggressive but without metastatic potential. It occurs particularly in the skin, deep soft tissue, retroperitoneum, mediastinum, and rarely in bone. Although lesions occur solitary, they often involve large areas of the body, such as the head/neck region (40%), trunk (30%), or extremity (30%).

Usually, it is present at birth as a flat, reddish-purple, tense and edematous lesion.

Although half of lesions are congenital, 58% of KHE develop during infancy, 32% between age 1 and 10 years (32%) and 10% after 11 years of age. Moreover, adult onset has been described too with mainly males being affected. Both sexes are affected equally in children.

Lesions are often greater than 5 cm in diameter and can cause visible deformity and pain. During early childhood, KHE may enlarge and after 2 years of age, it may partially regress. Though, it usually persists longterm. In addition, 50% of patients suffer from coagulopathy due to thrombocytopenia (<25,000/mm3), presenting with petechiae and bleeding. This is called the Kasabach-Merritt Phenomenon, which is caused by trapping of platelets and other clotting factors within the tumor. Kasabach-Merritt Phenomenon is less likely in patients with lesions less than 8 cm. As two-thirds of adult-onset KHE tumors are less than 2 cm, KHE in adults is rarely associated with Kasabach-Merritt Phenomenon.

Patients with KHE and Kasabach-Merritt Phenomenon present with petechiae and ecchymosis.

Most KHE tumors are diffuse involving multiple tissue planes and important structures. Resection of KHE is thus often difficult. Treatment of kaposiform hemangioendothelioma is therefore medical. The primary drug is interferon alfa, which is successful in 50% of children. Another option is vincristine, which has lots of side-effects, but has a response rate of 90%. Drug therapy is often used in shrinking the tumor and treating the coagulopathy. However, many of these kaposiform hemangioendotheliomas do not completely regress and remain as a much smaller asymptomatic tumor. However, KHE still has a high mortality rate of 30%. Although complete surgical removal with a large margin has the best reported outcome, it is usually not done because of the risk of bleeding, extensiveness, and the anatomic site of the lesion.

Operative management may be possible for small or localized lesions. Removal of larger areas also may be indicated for symptomatic patients or for patients who have failed farmacotherapy. Resection is not required for lesions that are not causing functional problems, because KHE is benign and because resection could cause deformity.

Acrogeria is extremely rare, with only about 40 cases having been reported in the medical literature, since 1941.

The key for managing Sack–Barabas syndrome is for the patient to be aware of their disease. Close follow up and planning of interventions can significantly prolong and maintain the quality of life of a patient with this disease.

Pregnant affected women must take special care due to the increased risk of premature death due to rupture of arteries, bowel or uterine rupture with a reported mortality rate of 50%.

Genetic counselling is recommended for prospective parents with a family history of Ehlers–Danlos syndrome. Affected parents should be aware of the type of Ehlers-Danlos syndrome they have and its mode of inheritance.

Eosinophils are a kind of a white blood cell which help protect the body from certain infections and involved in allergic responses. Eosionphelia is an abnormal increase of eosinophils in tissue, blood or both and is present in individuals born with this syndrome.

There has been a great deal of research to understand the cause of PHACE Syndrome. The abnormalities associated with this syndrome are thought to be due to errors that occur very early during development. Unfortunately, why the errors occur, or the exact cause is still unknown. PHACE has a shared biology of other vascular anomalies. There may be a genetic component involved and studies are underway to investigate this idea. No familial cases have been identified to date. Research is ongoing to find the cause of all vascular anomalies including PHACE Syndrome.