Diagnosis involves consideration of physical features and genetic testing. Presence of split uvula is a differentiating characteristic from Marfan Syndrome, as well as the severity of the heart defects. Loeys-Dietz Syndrome patients have more severe heart involvement and it is advised that they be treated for enlarged aorta earlier due to the increased risk of early rupture in Loeys-Dietz patients. Because different people express different combinations of symptoms and the syndrome was identified in 2005, many doctors may not be aware of its existence, although clinical guidelines were released in 2014-2015. Dr. Harold Dietz, Dr. Bart Loeys, and Dr. Kenneth Zahka are considered experts in this condition.

During pregnancy, even in the absence of preconception cardiovascular abnormality, women with Marfan syndrome are at significant risk of aortic dissection, which is often fatal even when rapidly treated. Women with Marfan syndrome, then, should receive a thorough assessment prior to conception, and echocardiography should be performed every six to 10 weeks during pregnancy, to assess the aortic root diameter. For most women, safe vaginal delivery is possible.

Marfan syndrome is expressed dominantly. This means a child with one parent a bearer of the gene has a 50% probability of getting the syndrome. In 1996, the first preimplantation genetic testing (PGT) therapy for Marfan was conducted; in essence PGT means conducting a genetic test on early-stage IVF embryo cells and discarding those embryos affected by the Marfan mutation.

In 2010 the Ghent nosology was revised, and new diagnostic criteria superseded the previous agreement made in 1996. The seven new criteria can lead to a diagnosis:

In the absence of a family history of MFS:

1. Aortic root Z-score ≥ 2 AND ectopia lentis

2. Aortic root Z-score ≥ 2 AND an FBN1 mutation

3. Aortic root Z-score ≥ 2 AND a systemic score* > 7 points

4. Ectopia lentis AND an FBN1 mutation with known aortic pathology

In the presence of a family history of MFS (as defined above):

1. Ectopia lentis

2. Systemic score* ≥ 7

3. Aortic root Z-score ≥ 2

- Points for systemic score:

- Wrist AND thumb sign = 3 (wrist OR thumb sign = 1)

- Pectus carinatum deformity = 2 (pectus excavatum or chest asymmetry = 1)

- Hindfoot deformity = 2 (plain pes planus = 1)

- Dural ectasia = 2

- Protrusio acetabuli = 2

- pneumothorax = 2

- Reduced upper segment/lower segment ratio AND increased arm/height AND no severe scoliosis = 1

- Scoliosis or thoracolumbar kyphosis = 1

- Reduced elbow extension = 1

- Facial features (3/5) = 1 (dolichocephaly, enophthalmos, downslanting palpebral fissures, malar hypoplasia, retrognathia)

- Skin striae (stretch marks) = 1

- Myopia > 3 diopters = 1

- Mitral valve prolapse 1⁄4 1

The thumb sign (Steinberg's sign) is elicited by asking the patient to flex the thumb as far as possible and then close the fingers over it. A positive thumb sign is where the entire distal phalanx is visible beyond the ulnar border of the hand, caused by a combination of hypermobility of the thumb as well as a thumb which is longer than usual.

The wrist sign (Walker's sign) is elicited by asking the patient to curl the thumb and fingers of one hand around the other wrist. A positive wrist sign is where the little finger and the thumb overlap, caused by a combination of thin wrists and long fingers.

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.

Ultrasound remains as one of the only effective ways of prenatally diagnosing Larsen syndrome. Prenatal diagnosis is extremely important, as it can help families prepare for the arrival of an infant with several defects. Ultrasound can capture prenatal images of multiple joint dislocations, abnormal positioning of legs and knees, depressed nasal bridge, prominent forehead, and club feet. These symptoms are all associated with Larsen syndrome, so they can be used to confirm that a fetus has the disorder.

In terms of the diagnosis of arterial tortuosity syndrome can be done via genetic testing, as well as the following listed below:

- CT

- MRI

- Echocardiogram

- Physical exam(for specific characteristics)

The treatment of arterial tortuosity syndrome entails possible surgery for aortic aneurysms, as well as, follow ups which should consist of EGC. The prognosis of this condition has it at about 12% mortality

If the medical history and the actual exam of the hemangioma look typical for PHACE Syndrome, more tests are ordered to confirm the diagnosis. These tests may include:

- Ultrasound

- Magnetic resonance imaging (MRI)

- Magnetic resonance angiography of the brain (MRA)

- Echocardiogram

- Eye exam by an eye doctor

- Other tests may be needed for diagnosis and treatment

Treatment for Larsen syndrome varies according to the symptoms of the individual. Orthopedic surgery can be performed to correct the serious joint defects associated with Larsen syndrome. Reconstructive surgery can be used to treat the facial abnormalities. Cervical kyphosis can be very dangerous to an individual because it can cause the vertebrae to disturb the spinal cord. Posterior cervical arthrodesis has been performed on patients with cervical kyphosis, and the results have been successful Propranolol has been used to treat some of the cardiac defects associated with Marfan's syndrome, so the drug also has been suggested to treat cardiac defects associated with Larsen syndrome.

MASS syndrome a medical disorder similar to Marfan syndrome.

MASS stands for: mitral valve prolapse, aortic root diameter at upper limits of normal for body size, stretch marks of the skin, and skeletal conditions similar to Marfan syndrome. MASS Phenotype is a connective tissue disorder that is similar to Marfan syndrome. It is caused by a similar mutation in the gene called fibrillin-1 that tells the body how to make an important protein found in connective tissue. This mutation is an autosomal dominant mutation in the FBN1 gene that codes for the extracellular matrix protein fibrillin-1; defects in the fibrillin-1 protein cause malfunctioning microfibrils that result in improper stretching of ligaments, blood vessels, and skin.

Someone with MASS phenotype has a 50 percent chance of passing the gene along to each child.

People with features of MASS Phenotype need to see a doctor who knows about connective tissue disorders for an accurate diagnosis; often this will be a medical geneticist. It is very important that people with MASS Phenotype get an early and correct diagnosis so they can get the right treatment. Treatment options for MASS phenotype are largely determined on a case-by-case basis and generally address the symptoms as opposed to the actual disorder; furthermore, due to the similarities between these two disorders, individuals with MASS phenotype follow the same treatment plans as those with Marfan syndrome.

MASS stands for the Mitral valve, myopia, Aorta, Skin and Skeletal features of the disorder. MASS Phenotype affects different people in different ways.

In MASS Phenotype:

Mitral valve prolapse may be present. This is when the flaps of one of the heart’s valves (the mitral valve, which regulates blood flow on the left side of the heart) are “floppy” and don’t close tightly. Aortic root diameter may be at the upper limits of normal for body size, but unlike Marfan syndrome there is not progression to aneurysm or predisposition to dissection. Skin may show stretch marks unrelated to weight gain or loss (striae). Skeletal features, including curvature of the spine (scoliosis), chest wall deformities, and joint hypermobility, may be present. People with MASS Phenotype do not have lens dislocation but have myopia, also known as nearsightedness.

MASS syndrome and Marfan syndrome are overlapping connective tissue disorders. Both can be caused by mutations in the gene encoding a protein called fibrillin. These conditions share many of the same signs and symptoms including long limbs and fingers, chest wall abnormalities (indented chest bone or protruding chest bone), flat feet, scoliosis, mitral valve prolapse, loose or hypextensible joints, highly arched roof of the mouth, and mild dilatation of the aortic root.

Individuals with MASS syndrome do not have progressive aortic enlargement or lens dislocation, while people with Marfan syndrome do. Skin involvement in MASS syndrome is typically limited to stretch marks (striae distensae). Also, the skeletal symptoms of MASS syndrome are generally mild.

Although LFS is usually suspected when intellectual disability and marfanoid habitus are observed together in a patient, the diagnosis of LFS can be confirmed by the presence of the p.N1007S missense mutation in the "MED12" gene.

In the differential diagnosis of LFS, another disorder that exhibits some features and symptoms of LFS and is also associated with a missense mutation of "MED12" is Opitz-Kaveggia syndrome (FGS). Common features shared by both LFS and FGS include X-linked intellectual disability, hyperactivity, macrocephaly, corpus callosum agenesis and hypotonia. Notable features of FGS that have not been reported with LFS include excessive talkativness, consistent strength in socialization skills, imperforate anus (occlusion of the anus) and ocular hypertelorism (extremely wide-set eyes).

Whereas LFS is associated with missense mutation p.N1007S, FGS is associated with missense mutation p.R961W. As both disorders originate from an identical type of mutation in the same gene, while exhibiting similar, yet distinct characteristics; LFS and FGS are considered to be allelic. In the context of "MED12", this suggests that the phenotype of each disorder is related to the way in which their respective mutations alter the "MED12" sequence and its function.

Brain MRI shows vermis atrophy or hypoplasic. Cerebral and cerebellar atrophy with white matter changes in some cases.

Smith (2015) conducted a study that looked into specific biological markers that correlate to Moyamoya disease. Some of the categories of these biomarkers include phenotypes - conditions commonly related to Moyamoya, radiographical markers for the diagnosis of Moyamoya, and proteins as well as cellular changes that occur in cases of Moyamoya.

Similar to Moyamoya Disease, there are conditions that are closely associated with Moyamoya Syndrome. Some of the more common medical conditions that are closely associated with Moyamoya Syndrome include trisomy 21 (Down's Syndrome), sickle cell disease, and neurofibromatosis type 1. There is also evidence that identifies hyperthyroidism and congenital dwarfing syndromes as two of the more loosely associated syndromes that correlate with the possibility of being diagnosed with Moyamoya Disease later in life.

There is also research that has shown that certain radiographic biomarkers that lead to the diagnosis of Moyamoya Disease have been identified. The specific radiographic markers are now considered an acceptable key component to Moyamoya Disease and have been added to the INternational Classification of Diseases (ICD). These biomarkers of Moyamoya are "stenosis of the distal ICA's up to and including the bifurcation, along with segments of the proximal ACA and MCA...dilated basal collateral vessels must be present" Some other common findings that have not been added to the classification index of those with Moyamoya Disease which are found using radiography involve very distinct changes in the vessels of the brain. These changes include newly formed vessels made to compensate for another change noted, ischemia and cerebrovascular reserve, both found on MRI. Functional changes include evidence of ischemia in vessels of the brain (ICA, ACA, MCA, specifically). It is important to also note that the radiographic biomarkers, in order to be classified as Moyamoya Disease, all findings must be bilateral. If this is not the case and the findings are unilateral, it is diagnosed as Moyamoya Syndrome.

There are also several protein biomarkers that have been linked to the Moyamoya Disease diagnosis. Although the sample size of the studies performed are small due to the rarity of the disease, the findings are indicative of a correlation between the disease and several specific protein biomarkers. Other studies have confirmed the correlation of Moyamoya and adhesion molecule 1 (ICAM-1) being increased as compared to normal vascular function counterparts Furthermore, it has been concluded that the localization of inflammatory cells suggests that the inflammation stimulus iteself may be responsible for the proliferation and occlusion in the ICA, ACA, and MCA found in those with Moyamoya Disease.

Usually the hemangioma requires medical therapy. The child may need other therapies, depending on what other organs or structures are involved.

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.

Since the cause of FAD has not been genetically pinpointed, the only way to diagnose FAD is through the examination of phenotypic variations in the aorta. Usually echocardiography is used to take measurements of the aortic root as well as transesophageal echocardiography. Biomarkers lend a quick way to diagnose dissection when time is of the essence. These have the ability to relay the levels of smooth muscle mysosin heavy chain protein present, which is released from damaged aortic tissue.

There are two types of FAD; groups A and B. Normally if any area of the ascending aorta is involved in the dissection this is considered group A. If the dissection occurs within the descending aorta this is classified in group B. These two groups can than be broken down into three classes of FAD: Type 1, Type 2 and Type 3. Group A consists of Types 1 and 2, whereas Group B consists only of Type 3. Type 1 encompasses dissection in the distal ascending aorta closest to the heart, not including the aortic arch. Type 2 refers to dissection of the ascending aorta, closer to and including the aortic arch. Type 3 refers to the descending thoracic and abdominal aorta.

Group A dissections are the more serious of the two due to the location of the dissection in the ascending aorta, which leads to a higher risk of congestive heart failure and pericardium and/or aortic valve rupture. Individuals also tend to be predisposed to type A if they do have Marfans or Elhers-Danlos syndromes. These contribute to a higher fatality rate in group A dissection if immediate surgery is not performed. The most common corrective surgeries are actual aortic valve replacement and coronary artery bypass. The five year survival rate after surgery is a successful 70.4% due to vigilant monthly physical exams and chest x-rays to monitor progress. Group B dissections typically have a higher surgery mortality rate and are therefore not good candidates. Instead medical management is the common response to treating and keeping dissections of the descending aorta under control.

Diagnosis is often confirmed by several abnormalities of skeletal origin. There is a sequential order of findings, according to Cormode et al., which initiate in abnormal cartilage calcification and later brachytelephalangism. The uniqueness of brachytelephalangy in KS results in distinctively broadened and shortened first through fourth distal phalanges, while the fifth distal phalanx bone remains unaffected. Radiography also reveals several skeletal anomalies including facial hypoplasia resulting in underdevelopment of the nasal bridge with noticeably diminished alae nasi. In addition to distinguishable facial features, patients generally demonstrate shorter than average stature and general mild developmental delay.

The diagnosis of moyamoya is suggested by CT, MRI, or angiogram results. Contrast-enhanced T1-weighted images are better than FLAIR images for depicting the leptomeningeal ivy sign in moyamoya disease. MRI and MRA should be performed for the diagnosis and follow-up of moyamoya disease. Diffusion-weighted imaging can also be used for following the clinical course of children with moyamoya disease, in whom new focal deficits are highly suspicious of new infarcts.

Proliferation of smooth muscle cells in the walls of the Moyamoya affected arteries has been found to be representative of the disease. A study of six autopsies of six patients who died from Moyamoya disease lead to the finding that there is evidence that supports the theory that there is a thickening, or proliferation, of the innermost layer of the vessels affected by Moyamoya. These vessels are the ACA (anterior cerebral artery), MCA (middle cerebral artery), and ICA (internal carotid artery). The occlusion of the ICA results in concomitant diminution of the "puff-of-smoke" collaterals, as they are supplied by the ICA.

Often nuclear medicine studies such as SPECT (single photon emission computerized tomography) are used to demonstrate the decreased blood and oxygen supply to areas of the brain involved with moyamoya disease. Conventional angiography provided the conclusive diagnosis of moyamoya disease in most cases and should be performed before any surgical considerations.

Dr. Darren B. Orbach, MD, PhD explains how the disease progresses as well as the role angiography plays in detecting the progression of Moyamoya in a short video

Currently, there is controversy over whether or not inheritance truly plays a role in FAD, and if so which gene it acts upon. FAD does not come from strictly one predisposing factor, such as hypertension. It is suggested that the combination of environmental factors along with genetics may contribute to causing FAD. Before newer and more effective cures and therapies can be developed, first the specific gene mutation must be identified. Until such a gene is determined, scientists say patient education, and physician awareness is vital. Currently scientists have found animal models to be beneficial in understanding the pathology behind FAD. In the future there is hope to develop drugs that will better support and strengthen the aortic wall. Endovascular methods of treatment are becoming increasingly popular, and scientists hope to use this technique in both acute and chronic cases.

Treatment is with neonatal surgical repair, with the objective of restoring a normal pattern of blood flow. The surgery is open heart, and the patient will be placed on cardiopulmonary bypass to allow the surgeon to work on a still heart. The heart is opened and the ventricular septal defect is closed with a patch. The pulmonary arteries are then detached from the common artery (truncus arteriosus) and connected to the right ventricle using a tube (a conduit or tunnel). The common artery, now separated from the pulmonary circulation, functions as the aorta with the truncal valve operating as the aortic valve. Most babies survive this surgical repair, but may require further surgery as they grow up. For example, the conduit does not grow with the child and may need to be replaced as the child grows. Furthermore, the truncal valve is often abnormal and may require future surgery to improve its function.

There have been cases where the condition has been diagnosed at birth and surgical intervention is an option. A number of these cases have survived well into adulthood.

The U.S. Preventive Services Task Force recommends a single screening ultrasound for abdominal aortic aneurysm in males age 65 to 75 years who have a history of smoking. There is an estimated number needed to screen of approximately 850 people. It is unclear if screening is useful in women aged 65 to 75 who have smoked and they recommend against screening in women who have never smoked.

Repeat ultrasounds should be carried out in those who have an aortic size greater than 3.0 cm. In those whose aorta is between 3.0 and 3.9 cm this should be every three years, if between 4.0 and 4.4 cm every two year, and if between 4.5 and 5.4 cm every year.

In the United Kingdom one time screening is recommended in all males over 65 years of age. Australia has no guideline on screening.

Familial thoracic aortic aneurysm is an autosomal dominant disorder of large arteries.

There is an association between familial thoracic aortic aneurysm, Marfan syndrome and massive baclofen overdose as well as other hereditary connective tissue disorders.

Sneddon's patients are generally treated with warfarin, maintaining a high INR of 3-4. Because most will experience significant relief of symptoms after several months of consistent INR in this range, treatment with warfarin is often used as a diagnostic tool.

There are no diagnostic tests on which all Sneddon's patients will have abnormal results, although brain MRI and skin biopsy are often abnormal. The diagnosis is based on a detailed history and physical examination. About 40-60% of patients with the syndrome test positive for antiphospholipid antibodies.