Management of the underlying defect is proportional to the severity of the clinical presentation. Leg swelling and pain is best evaluated by vascular specialists (vascular surgeons, interventional cardiologists, interventional radiologists) who both diagnose and treat arterial and venous diseases to ensure that the cause of the extremity pain is evaluated. The diagnosis needs to be confirmed with some sort of imaging that may include magnetic resonance venography, venogram and usually confirmed with intravascular ultrasound because the flattened vein may not be noticed on conventional venography. In order to prevent prolonged swelling or pain from the consequences of the backed up blood from the compressed iliac vein, flow needs to be improved out of the leg. Uncomplicated cases may be managed with compression stockings.

Severe May-Thurner syndrome may require thrombolysis if there is a recent onset of thrombosis, followed by angioplasty and stenting of the iliac vein after confirming the diagnosis with a venogram or an intravascular ultrasound. A stent may be used to support the area from further compression following angioplasty. As the name implies, there classically is not a thrombotic component in these cases, but thrombosis may occur at any time.

If the patient has extensive thrombosis, it may be appropriate to consider pharmacologic and/or mechanical (also known as pharmacomechanical) thrombectomy. This is currently being studied to determine whether this will decrease the incidence of post-thrombotic syndrome.

In medicine, May-Thurner syndrome (MTS), also known as the iliac vein compression syndrome, is a rare condition in which compression of the common venous outflow tract of the left lower extremity may cause discomfort, swelling, pain or blood clots, called deep venous thrombosis (DVT), in the iliofemoral vein.

The specific problem is compression of the left common iliac vein by the overlying right common iliac artery. This leads to pooling or stasis of blood, predisposing the individual to the formation of blood clots. Uncommon variations of MTS have been described, such as the right common iliac vein getting compressed by the right common iliac artery.

In the 21st century the May-Thurner syndrome definition has been expanded to a broader disease profile known as nonthrombotic iliac vein lesions (NIVL) which can involve both the right and left iliac veins as well as multiple other named venous segments. This syndrome frequently manifests as pain when the limb is dependent (hanging down the edge of a bed/chair) and/or significant swelling of the whole limb.

The 2012 ACCP guidelines offered weak recommendations. For at-risk long-haul travelers—those with "previous VTE, recent surgery or trauma, active malignancy, pregnancy, estrogen use, advanced age, limited mobility, severe obesity, or known thrombophilic disorder"—suggestions included calf exercises, frequent walking, and aisle seating in airplanes to ease walking. The use of graduated compression stockings that fit below the knee and give 15–30 mm Hg of pressure to the ankle was suggested, while aspirin or anticoagulants were not. Compression stockings have sharply reduced the levels of asymptomatic DVT in airline passengers, but the effect on symptomatic VTE is unknown, as none of the individuals studied developed symptomatic VTE.

Major orthopedic surgery—total hip replacement, total knee replacement, or hip fracture surgery—has a high risk of causing VTE. If prophylaxis is not used after these surgeries, symptomatic VTE has about a 4% chance of developing within 35 days. Options for VTE prevention in people follow nonorthopedic surgery include early walking, mechanical prophylaxis (intermittent pneumatic compression or graduated compression stockings), and drugs (low-molecular-weight heparin and low-dose-unfractionated heparin) depending upon the risk of VTE, risk of major bleeding, and person's preferences. Following major orthopedic surgery, the ACCP recommends treatment with drugs that reduce the risk of clots (such as fondaparinux and aspirin) with low-molecular-weight heparin (LMWH) suggested as a preference. Intermittent pneumatic compression is also an option. Graduated compression stockings are effective after both general and orthopedic surgery.

A minority of patients can be treated medically with sodium restriction, diuretics to control ascites, anticoagulants such as heparin and warfarin, and general symptomatic management. The majority of patients require further intervention. Milder forms of Budd–Chiari may be treated with surgical shunts to divert blood flow around the obstruction or the liver itself. Shunts must be placed early after diagnosis for best results. The TIPS is similar to a surgical shunt: it accomplishes the same goal but has a lower procedure-related mortality—a factor that has led to a growth in its popularity. If all the hepatic veins are blocked, the portal vein can be approached via the intrahepatic part of inferior vena cava, a procedure called DIPS (direct intrahepatic portocaval shunt). Patients with stenosis or vena caval obstruction may benefit from angioplasty. Limited studies on thrombolysis with direct infusion of urokinase and tissue plasminogen activator into the obstructed vein have shown moderate success in treating Budd–Chiari syndrome; however, it is not routinely attempted.

Liver transplantation is an effective treatment for Budd–Chiari. It is generally reserved for patients with fulminant liver failure, failure of shunts or progression of cirrhosis that reduces the life expectancy to 1 year. Long-term survival after transplantation ranges from 69–87%. The most common complications of transplant include rejection, arterial or venous thromboses and bleeding due to anticoagulation. Up to 10% of patients may have a recurrence of Budd–Chiari syndrome after the transplant.

As there is no known cure, Loeys–Dietz syndrome is a lifelong condition. Due to the high risk of death from aortic aneurysm rupture, patients should be followed closely to monitor aneurysm formation, which can then be corrected with interventional radiology or vascular surgery.

Previous research in laboratory mice has suggested that the angiotensin II receptor antagonist losartan, which appears to block TGF-beta activity, can slow or halt the formation of aortic aneurysms in Marfan syndrome. A large clinical trial sponsored by the National Institutes of Health is currently underway to explore the use of losartan to prevent aneurysms in Marfan syndrome patients. Both Marfan syndrome and Loeys–Dietz syndrome are associated with increased TGF-beta signaling in the vessel wall. Therefore, losartan also holds promise for the treatment of Loeys–Dietz syndrome. In those patients in which losartan is not halting the growth of the aorta, irbesartan has been shown to work and is currently also being studied and prescribed for some patients with this condition.

If an increased heart rate is present, atenolol is sometimes prescribed to reduce the heart rate to prevent any extra pressure on the tissue of the aorta. Likewise, strenuous physical activity is discouraged in patients, especially weight lifting and contact sports.

Several studies have attempted to predict the survival of patients with Budd–Chiari syndrome. In general, nearly 2/3 of patients with Budd–Chiari are alive at 10 years. Important negative prognostic indicators include ascites, encephalopathy, elevated Child-Pugh scores, elevated prothrombin time, and altered serum levels of various substances (sodium, creatinine, albumin, and bilirubin). Survival is also highly dependent on the underlying cause of the Budd–Chiari syndrome. For example, a patient with an underlying myeloproliferative disorder may progress to acute leukemia, independently of Budd–Chiari syndrome.

Catastrophic antiphospholipid syndrome (CAPS), also known as Asherson's syndrome, is an acute and complex biological process that leads to occlusion of small vessels of various organs. It was first described by Ronald Asherson in 1992. The syndrome exhibits thrombotic microangiopathy, multiple organ thrombosis, and in some cases tissue necrosis and is considered an extreme or catastrophic variant of the antiphospholipid syndrome.

CAPS has a mortality rate of about 50%. With the establishment of a CAPS-Registry more has been learned about this syndrome, but its cause remains unknown. Infection, trauma, medication, and/or surgery can be identified in about half the cases as a "trigger". It is thought that cytokines are activated leading to a cytokine storm with the potentially fatal consequences of organ failure. A low platelet count is a common finding. Individuals with CAPS often exhibit a positive test to antilipid antibodies, typically IgG, and may or may not have a history of lupus or another connective tissue disease. Association with another disease such as lupus is called a secondary APS unless it includes the defining criteria for CAPS.

Clinically, the syndrome affects at least three organs and may affect many organs systems. Peripheral thrombosis may be encountered affecting veins and arteries. Intraabdominal thrombosis may lead to pain. Cardiovascular, nervous, kidney, and lung system complications are common. The affected individual may exhibit skin purpura and necrosis. Cerebral manifestations may lead to encephalopathy and seizures. Myocardial infarctions may occur. Strokes may occur due to the arterial clotting involvement. Death may result from multiple organ failure.

Treatments may involve the following steps:

- Prevention includes the use of antibiotics for infection and parenteral anticoagulation for susceptible patients.

- Specific therapy includes the use of intravenous heparin and corticosteroids, and possibly plasma exchanges, intravenous immunoglobulin.

- Additional steps may have to be taken to manage circulatory problems, kidney failure, and respiratory distress.

- When maintaining survival of the disease treatments also include high doses of Rituxan (Rituximab) to maintain stability.

Conservative treatment of CVI in the leg involves symptomatic treatment and efforts to prevent the condition from getting worse instead of effecting a cure. This may include

- Manual compression lymphatic massage therapy

- Skin lubrication

- Sequential compression pump

- Ankle pump

- Compression stockings

- Blood pressure medicine

- Frequent periods of rest elevating the legs above the heart level

- Tilting the bed so that the feet are above the heart. This may be achieved by using a 20 cm (7-inch) bed wedge or sleeping in a 6 degree Trendelenburg position. Obese or pregnant patients might be advised by their physicians to forgo the tilted bed.

Venous Insufficiency Conservative, Hemodynamic and Ambulatory treatment" is an ultrasound guided, minimally invasive surgery strategic for the treatment of varicose veins, performed under local anaesthetic. CHIVA is an abbreviation from the French "Cure Conservatrice et Hemodynamique de l'Insufficience Veineuse en Ambulatoire".

Harlequin syndrome is not debilitating so treatment is not normally necessary. In cases where the individual may feel socially embarrassed, contralateral sympathectomy may be considered, although compensatory flushing and sweating of other parts of the body may occur. In contralateral sympathectomy, the nerve bundles that cause the flushing in the face are interrupted. This procedure causes both sides of the face to no longer flush or sweat. Since symptoms of Harlequin syndrome do not typically impair a person’s daily life, this treatment is only recommended if a person is very uncomfortable with the flushing and sweating associated with the syndrome.

Loeys–Dietz syndrome (LDS) is an autosomal dominant genetic connective tissue disorder. It has features similar to Marfan syndrome and Ehlers–Danlos syndrome. The disorder is marked by aneurysms in the aorta, often in children, and the aorta may also undergo sudden dissection in the weakened layers of the wall of aorta. Aneurysms and dissections also can occur in arteries other than the aorta. Because aneurysms in children tend to rupture early, children are at greater risk for dying if the syndrome is not identified. Surgery to repair aortic aneurysms is essential for treatment.

There are four types of the syndrome, labelled types I through IV, which are distinguished by their genetic cause. Type 1, Type 2, Type 3, and Type 4 are caused by mutations in "TGFBR1", "TGFBR2", "SMAD3", and "TGFB2" respectively. These four genes encoding transforming growth factors play a role in cell signaling that promotes growth and development of the body's tissues. Mutations of these genes cause production of proteins without function. Although the disorder has an autosomal pattern of inheritance, this disorder results from a new gene mutation in 75% of cases and occurs in people with no history of the disorder in their family.

Loeys-Dietz syndrome was identified and characterized by pediatric geneticists Bart Loeys and Harry Dietz at Johns Hopkins University in 2005.

Studies have shown that patients with Pacemaker syndrome and/or with sick sinus syndrome are at higher risk of developing fatal complications that calls for the patients to be carefully monitored in the ICU. Complications include atrial fibrillation, thrombo-embolic events, and heart failure.

In August 2016, researchers at the Instituto de Assistência dos Servidores do Estado do Rio de Janeiro used botulinum toxin as a method to block the acetylcholine release from the presynaptic neurons. Although they have seen a reduction in one sided flushing, sweating still occurs.

There have been case studies of individuals whom have experienced this syndrome after an operation. Two patients, a 37-year-old and 58-year-old female patients suffering from metastatic cancer were scheduled for placement of an intrathecal pump drug delivery system. After the intrathecal pump was placed, certain medications were given to the patients. Once the medications were administered, both patients had one sided facial flushes, closely resembling Harlequin Syndrome. Patients were given neurological exams to confirm that their nerves were still intact. An MRI was performed and showed no significant evidence of bleeding or nerve compression. After close observation for 16 hours, symptoms of the Harlequin syndrome was diminished and both patients did not have another episode.

Another case study was based on a 6-year-old male visiting an outpatient setting for one sided flushes during or after physical activity or exposed to heat. Vitals, laboratory tests, and CT scans were normal. Along with the flushes, the right pupil was 1.5 mm in size, while the left pupil was 2.5 mm in size; however, no ptosis, miosis, or enophthalmos was noted. The patient also had an MRI scan to rule out any lesion near the brain or spinal cord. No abnormalities were noted and the patient did not receive any treatments. The patient was diagnosed with idiopathic Harlequin syndrome.

Although the mechanism is still unclear, the pathophysiology of this condition, close monitoring, and reassurance are vital factors for successful management.

Successful treatment of the associated underlying disorder, such as GORD or hiatus hernia, may provide relief.

Diet alone cannot treat pacemaker syndrome, but an appropriate diet to the patient, in addition to the other treatment regimens mentioned, can improve the patient's symptoms. Several cases mentioned below:

- For patients with heart failure, low-salt diet is indicated.

- For patients with autonomic insufficiency, a high-salt diet may be appropriate.

- For patients with dehydration, oral fluid rehydration is needed.

Sandifer syndrome is not typically life-threatening and the prognosis is typically good.

There has been no general recommendation for treatment of patients with Giant Platelet Disorders, as there are many different specific classifications to further categorize this disorder which each need differing treatments. Platelet transfusion is the main treatment for people presenting with bleeding symptoms. There have been experiments with DDAVP (1-deamino-8-arginine vasopressin) and splenectomy on people with Giant platelet disorders with mixed results, making this type of treatment contentious.

Treatment modality depends on the cause. Tumors may be removed surgically, but pituitary stalk interruption may persist. Usually, replacement of those hormones that are reduced due to failed feedback control systems will be necessary.

Because CHILD syndrome is a congenital disorder, the symptoms may be present at birth or may develop during the first few weeks of life and continue for the lifetime of the patient.

There is currently no treatment for CHILD syndrome so any treatment would target the symptoms currently present. Emoillents like Lac-Hydran (ammonium lactate) and Ureaphil (urea) are used to treat scaly patches on the skin. A pediatric orthopedic surgeon can evaluate any underdevelopment in the bones and treat them if necessary.

There is a compound that is a topical liquid that can calm lesions down on older adults and make them go away on younger children. The mixture was made by Dr. Amy Paller at Children's Hospital. It is mixed as follows: to make 250 ml: Grind up lovastatin tablets 5g (10-20-40-80 mg); mix with cholesterol NF powder (NDC# 51927-1203-00, PCCA) 5g; mix with preserved water while mixing (eventually mixing for 1/2 hour with electronic mortar and pestle) to bring to full volume with preserved water. 8 oz

If a contracture is less than 30 degrees, it may not interfere with normal functioning. The common treatment is splinting and occupational therapy. Surgery is the last option for most cases as the result may not be satisfactory.

If binocular vision is present and head position is correct, treatment is not obligatory.

Treatment is required for: visual symptoms, strabismus, or incorrect head position.

Acquired cases that have active inflammation of the superior oblique tendon may benefit from local corticosteroid injections in the region of the trochlea.

The goal of surgery is to restore free ocular rotations. Various surgical techniques have been used:

- Harold Brown advocated that the superior oblique tendon be stripped. A procedure named sheathotomy. The results of such a procedure are frequently unsatisfactory because of reformation of scar tissue.

- Tenotomy of the superior oblique tendon (with or with out a tendon spacer) has also been advocated. This has the disadvantage that it frequently produces a superior oblique paresis.

- Weakening of the inferior oblique muscle of the affected eye may be needed to compensate for iatrogenic fourth nerve palsy.

During surgery, a traction test is repeated until the eye rotations are free and the eye is anchored in an elevated adducted position for about two weeks after the surgery. This maneuver is intended to prevent the reformation of scar tissue in the same places. Normalization of head position may occur but restoration of full motility is seldom achieved. A second procedure may be required.

It can result in many abnormal heart rhythms (arrhythmias), including sinus arrest, sinus node exit block, sinus bradycardia, and other types of bradycardia (slow heart rate).

Sick sinus syndrome may also be associated with tachycardias (fast heart rate) such as atrial tachycardia (PAT) and atrial fibrillation. Tachycardias that occur with sick sinus syndrome are characterized by a long pause after the tachycardia. Sick sinus syndrome is also associated with azygos continuation of interrupted inferior vena cava.

At the 2005 American Society of Human Genetics meeting, Francis Collins gave a presentation about a treatment he devised for children affected by Progeria. He discussed how farnesyltransferase inhibitor (FTI) affects H-Ras. After his presentation, members of the Costello Syndrome Family Network discussed the possibility of FTIs helping children with Costello syndrome. Mark Kieran, who presented at the 1st International Costello Syndrome Research Symposium in 2007, agreed that FTIs might help children with Costello syndrome. He discussed with Costello advocates what he had learned in establishing and running the Progeria clinical trial with an FTI, to help them consider next steps.

Another medication that affects H-Ras is Lovastatin, which is planned as a treatment for neurofibromatosis type I. When this was reported in mainstream news, the Costello Syndrome Professional Advisory Board was asked about its use in Costello Syndrome. Research into the effects of Lovastatin was linked with Alcino Silva, who presented his findings at the 2007 symposium. Silva also believed that the medication he was studying could help children with Costello syndrome with cognition.

A third medication that might help children with Costello syndrome is a MEK inhibitor that helps inhibit the pathway closer to the cell nucleus.