There is considerable variability in the phenotype of Loeys–Dietz syndrome, from mild features to severe systemic abnormalities. The primary manifestations of Loeys–Dietz syndrome are arterial tortuosity (winding course of blood vessels), widely spaced eyes (hypertelorism), wide or split uvula, and aneurysms at the aortic root. Other features may include cleft palate and a blue/gray appearance of the white of the eyes. Cardiac defects and club foot may be noted at birth.

There is overlap in the manifestations of Loeys–Dietz and Marfan syndromes, including increased risk of ascending aortic aneurysm and aortic dissection, abnormally long limbs and fingers, and dural ectasia (a gradual stretching and weakening of the dura mater that can cause abdominal and leg pain). Findings of hypertelorism (widely spaced eyes), bifrid or split uvula, and skin findings such as easy bruising or abnormal scars may distinguish Loys-Dietz from Marfan syndrome.

Findings of Loys-Dietz syndrome may include:

- Skeletal/spinal malformations: craniosynositosis, Scoliosis, spinal instability and spondylolisthesis, Kyphosis

- Sternal abnormalities: pectus excavatum, pectus carinatum

- Contractures of fingers and toes (camptodactyly)

- Long fingers and lax joints

- Weakened or missing eye muscles (strabismus)

- Club foot

- Premature fusion of the skull bones (craniosynostosis)

- Joint hypermobility

- Congenital heart problems including patent ductus arteriosus (connection between the aorta and the lung circulation) and atrial septal defect (connection between heart chambers)

- Translucency of the skin with velvety texture

- Abnormal junction of the brain and medulla (Arnold-Chiari malformation)

- Bicuspid aortic valves

- Criss-crossed pulmonary arteries

More than 30 different signs and symptoms are variably associated with Marfan syndrome. The most prominent of these affect the skeletal, cardiovascular, and ocular systems, but all fibrous connective tissue throughout the body can be affected.

Most of the readily visible signs are associated with the skeletal system. Many individuals with Marfan syndrome grow to above-average height, and some have disproportionately long, slender limbs with thin, weak wrists and long fingers and toes. Besides affecting height and limb proportions, people with Marfan syndrome may have abnormal lateral curvature of the spine (scoliosis), thoracic lordosis, abnormal indentation (pectus excavatum) or protrusion (pectus carinatum) of the sternum, abnormal joint flexibility, a high-arched palate with crowded teeth and an overbite, flat feet, hammer toes, stooped shoulders, and unexplained stretch marks on the skin. It can also cause pain in the joints, bones and muscles. Some people with Marfan have speech disorders resulting from symptomatic high palates and small jaws. Early osteoarthritis may occur. Other signs include limited range of motion in the hips due to the femoral head protruding into abnormally deep hip sockets.

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.

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.

Cardiac defects are similar to those associated with Marfan's syndrome, a disorder of the connective tissue.

- Elongation of aorta

- Bicuspid aortic valve

- Subaortic stenosis

- Mitral valve prolapse with mitral regurgitation

- Atrial septal defect

- Patent ductus arteriosus

- Tricuspid valve prolapse

- Aortic dissection and aneurysm

- Aneurysm of ductus arteriosus

These symptoms were found in rare cases of Larsen syndrome.

- Cataracts

- Cleft palate

- Extra bones of wrist

- Malocclusion

- Microdontia and hypodontia

- Complete agenesis of anus

- uterus

- Bifid tongue

LFS is clinically distinguished from other X-linked forms of intellectual disability by the accompanying presence of marfanoid habitus. Marfanoid habitus describes a group of physical features common to Marfan syndrome. Including Marfan syndrome and LFS, marfanoid features of this type have also been observed with several other disorders, one of which is multiple endocrine neoplasia type 2.

In LFS, specific features identified as marfanoid include: a long, narrow face; tall, thin stature; long, slender limbs, fingers and toes (not unlike arachnodactyly) with joint hyperextensibility, shortened halluces (the big toes) and long second toes.

The diagnosis of marfanoid habitus in LFS is often delayed because many of the physical features and characteristics associated with it are usually not evident until adolescence.

Hemangiomas associated with PHACE Syndrome are usually small or not visible at birth, but are easier to see during the first days to weeks of life. They can grow rapidly. Hemangiomas linked with PHACE Syndrome tend to cover a large area of the face, head or neck, either as one lesion or as many single lesions.

Craniofacial and other features of LFS include: maxillary hypoplasia (underdevelopment of the upper jaw bone), a small mandible (lower jaw bone) and receding chin, a high-arched palate (the roof of the mouth), with crowding and misalignment of the upper teeth; macrocephaly (enlarged skull) with a prominent forehead, hypernasal speech (voice), a long nose with a high, narrow nasal bridge; a deep, short philtrum (the indentation in the upper lip, beneath the nose), low-set ears with some apparent retroversion, hypotonia (decreased muscle tone), pectus excavatum (a malformity of the chest), slightly enlarged to normal testicular size in males, and seizures.

Hypernasal speech, or "hypernasality", is primarily the result of velopharyngeal insufficiency, a sometimes congenital aberration in which the velopharyngeal sphincter allows too much air into the nasal cavity during speech. In LFS, hypernasality may also be caused by failure of the soft palate and uvula to reach the back wall of the pharynx (the interior cavity of the throat where swallowing generally occurs) during speech, a condition that can be associated with a submucosal cleft palate.

As it grows, the hemangioma can break down skin, distort facial features or get in the way of other vital functions, such as breathing, vision, and hearing. Other complications will depend on what other structures are involved. These could include developmental delay, seizures, headaches, and abnormal muscle tone if the brain is involved.

Heyde's syndrome is a syndrome of gastrointestinal bleeding from angiodysplasia in the presence of aortic stenosis.

It is named after Edward C. Heyde, MD who first noted the association in 1958. It is caused by the induction of Von Willebrand disease type IIA (vWD-2A) by a depletion of Von Willebrand factor (vWF) in blood flowing through the narrowed valvular stenosis.

The signs and symptoms of DOCK8 deficiency are similar to the autosomal dominant form, STAT3 deficiency. However, in DOCK8 deficiency, there is no skeletal or connective tissue involvement, and affected individuals do not have the characteristic facial features of those with autosomal dominant hyper-IgE syndrome. DOCK8 deficient children often have eczema, respiratory and skin staphylococcus infections.

Beyond these, many other recurrent infections have been observed, including recurrent fungal infections and recurrent viral infections (including molluscum contagiosum, herpes simplex, and herpes zoster), recurrent upper respiratory infection (including "Streptococcus pneumoniae", "Haemophilus influenzae", respiratory syncytial virus, and adenovirus), recurrent sinusitis, recurrent otitis media, mastoiditis, pneumonia, bronchitis with bronchiectasis, osteomyelitis, candidiasis, meningitis (caused by cryptococcus or H. influenzae), pericarditis, salmonella enteritis, and giardiasis. Other dermatologic problems include squamous-cell carcinoma/dysplasia (vulvar, anal, and facial). Immune problems are also common, including autoimmune hemolytic anemia, severe allergies (both food and environmental), asthma, and reactive airway disease. The nervous system may also be affected; observed conditions in DOCK8 deficient people include hemiplegia, ischemic stroke, subarachnoid hemorrhage, and facial paralysis. Vascular complications are common, including aortic aneurysm, cerebral aneurysm, vessel occlusion and underperfusion, and leukocytoclastic vasculitis.

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.

It can be diagnosed with an echocardiogram. Patients will have a loss of appetite, turn pale, may feel cold in the lower half of the body due to not enough blood flow.

Patients with MALS reportedly experience abdominal pain, particularly in the epigastrium, which may be associated with eating and which may result in anorexia and weight loss.The pain can be in the left or right side, but usually where the ribs meet. Other signs are persistent nausea, lassitude (especially after a heavy meal) and exercise intolerance. Diarrhea is a common symptom, some experience constipation. While some experience vomiting, not everyone does. Exercise or certain postures can aggravate the symptoms. Occasionally, physical examination reveals an abdominal bruit in the mid-epigastrium.

Complications of MALS result from chronic compression of the celiac artery. They include gastroparesis and aneurysm of the pancreaticoduodenal arteries.

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.

In medicine, the median arcuate ligament syndrome (MALS, also known as celiac artery compression syndrome, celiac axis syndrome, celiac trunk compression syndrome or Dunbar syndrome) is a condition characterized by abdominal pain attributed to compression of the celiac artery and possibly the celiac ganglia by the median arcuate ligament. The abdominal pain may be related to meals, may be accompanied by weight loss, and may be associated with an abdominal bruit heard by a clinician.

The diagnosis of MALS is one of exclusion, as many healthy patients demonstrate some degree of celiac artery compression in the absence of symptoms. Consequently, a diagnosis of MALS is typically only entertained after more common conditions have been ruled out. Once suspected, screening for MALS can be done with ultrasonography and confirmed with computed tomography (CT) or magnetic resonance (MR) angiography.

Treatment is generally surgical, the mainstay being open division, or separation, of the median arcuate ligament combined with removal of the celiac ganglia. The majority of patients benefit from surgical intervention. Poorer responses to treatment tend to occur in patients of older age, those with a psychiatric condition or who use alcohol, have abdominal pain unrelated to meals, or who have not experienced weight loss.

It is sometimes called "Erdheim cystic medial necrosis of aorta", after Jakob Erdheim.

The term "cystic medial degeneration" is sometimes used instead of "cystic medial necrosis", because necrosis is not always found.

Familial aortic dissection or FAD refers to the splitting of the wall of the aorta in either the arch, ascending or descending portions. FAD is thought to be passed down as an autosomal dominant disease and once inherited will result in dissection of the aorta, and dissecting aneurysm of the aorta, or rarely aortic or arterial dilation at a young age. Dissection refers to the actual tearing open of the aorta. However, the exact gene(s) involved has not yet been identified. It can occur in the absence of clinical features of Marfan syndrome and of systemic hypertension. Over time this weakness, along with systolic pressure, results in a tear in the aortic intima layer thus allowing blood to enter between the layers of tissue and cause further tearing. Eventually complete rupture of the aorta occurs and the pleural cavity fills with blood. Warning signs include chest pain, ischemia, and hemorrhaging in the chest cavity. This condition, unless found and treated early, usually results in death. Immediate surgery is the best prognosis in most cases. FAD is not to be confused with PAU (penetrating atherosclerotic ulcers) and IMH (intramural hematoma), both of which present in ways similar to that of familial aortic dissection.

Heyde's syndrome is now known to be gastrointestinal bleeding from angiodysplasic lesions due to acquired vWD-2A deficiency secondary to aortic stenosis, and the diagnosis is made by confirming the presence of those three things. Gastrointestinal bleeding may present as bloody vomit, dark, tarry stool from metabolized blood, or fresh blood in the stool. In a person presenting with these symptoms, endoscopy, gastroscopy, and/or colonoscopy should be performed to confirm the presence of angiodysplasia. Aortic stenosis can be diagnosed by auscultation for characteristic heart sounds, particularly a crescendo-decrescendo (i.e., 'ejection') murmur, followed by echocardiography to measure aortic valve area (see diagnosis of aortic stenosis). While Heyde's syndrome may exist alone with no other symptoms of aortic stenosis, the person could also present with evidence of heart failure, fainting, or chest pain. Finally, Heyde's syndrome can be confirmed using blood tests for vWD-2A, although traditional blood tests for von Willebrand factor may result in false negatives due to the subtlety of the abnormality. The gold standard for diagnosis is gel electrophoresis; in people with vWD-2A, the large molecular weight von Willebrand factors will be absent from the SDS-agarose electrophoresis plate.

Interrupted aortic arch is a very rare heart defect (affecting 3 per million live births) in which the aorta is not completely developed. There is a gap between the ascending and descending thoracic aorta. In a sense it is the complete form of a coarctation of the aorta. Almost all patients also have other cardiac anomalies, including a ventricular septal defect (VSD), aorto-pulmonary window, and truncus arteriosus. Interrupted aortic arch is often associated with DiGeorge syndrome.

Double aortic arch (DAA) is a relatively rare congenital cardiovascular malformation. DAA is an of the aortic arch in which two aortic arches form a complete vascular ring that can compress the trachea and/or esophagus. Most commonly there is a larger (dominant) right arch behind and a smaller (hypoplastic) left aortic arch in front of the trachea/esophagus. The two arches join to form the descending aorta which is usually on the left side (but may be right-sided or in the midline). In some cases the end of the smaller left aortic arch closes (left atretic arch) and the vascular tissue becomes a fibrous cord. Although in these cases a complete ring of two patent aortic arches is not present, the term ‘vascular ring’ is the accepted generic term even in these anomalies.

The symptoms are related to the compression of the trachea, esophagus or both by the complete vascular ring. Diagnosis can often be suspected or made by chest x-ray, barium esophagram, or echocardiography. Computed tomography (CT) or magnetic resonance imaging (MRI) show the relationship of the aortic arches to the trachea and esophagus and also the degree of tracheal narrowing. Bronchoscopy can be useful in internally assessing the degree of tracheomalacia. Treatment is surgical and is indicated in all symptomatic patients. In the current era the risk of mortality or significant morbidity after surgical division of the lesser arch is low. However, the preoperative degree of tracheomalacia has an important impact on postoperative recovery. In certain patients it may take several months (up to 1–2 years) for the obstructive respiratory symptoms (wheezing) to disappear.

Symptoms are caused by vascular compression of the airway, esophagus or both. Presentation is often within the first month (neonatal period) and usually within the first 6 months of life. Starting at birth an inspiratory and expiratory stridor (high pitch noise from turbulent airflow in trachea) may be present often in combination with an expiratory wheeze. The severity of the stridor may depend on the patient’s body position. It can be worse when the baby is lying on his back rather than its side. Sometimes the stridor can be relieved by extending the neck (lifting the chin up). Parents may notice that the baby’s cry is hoarse and the breathing noisy. Frequently a persistent cough is present. When the airway obstruction is significant there may be episodes of severe cyanosis (“blue baby”) that can lead to unconsciousness. Recurrent respiratory infections are common and secondary pulmonary secretions can further increase the airway obstruction.

Secondary to compression of the esophagus babies often feed poorly. They may have difficulties in swallowing liquids with choking or regurgitating and increased respiratory obstruction during feeding. Older patients might refuse to take solid food, although most infants with severe symptoms nowadays are operated upon before they are offered solid food.

Occasionally patients with double aortic arches present late (during later childhood or adulthood). Symptoms may mimic asthma.

In mild cases, children may show no signs or symptoms at first and their condition may not be diagnosed until later in life. Some children born with coarctation of the aorta have other heart defects too, such as aortic stenosis, ventricular septal defect, patent ductus arteriosus or mitral valve abnormalities.

Coarctation is about twice as common in boys as it is in girls. It is common in girls who have Turner syndrome.

Symptoms may be absent with mild narrowings (coarctation). When present, they include: difficulty breathing, poor appetite or trouble feeding, failure to thrive. Later on, children may develop symptoms related to problems with blood flow and an enlarged heart. They may experience dizziness or shortness of breath, faint or near-fainting episodes, chest pain, abnormal tiredness or fatigue, headaches, or nosebleeds. They have cold legs and feet or have pain in their legs with exercise (intermittent claudication).

In more severe cases, where severe coarctations, babies may develop serious problems soon after birth because not enough blood can get through the aorta to the rest of their body.

Arterial hypertension in the arms with low blood pressure in the lower extremities is classic. In the lower extremities, weak pulses in the femoral arteries and arteries of the feet are found.

The coarctation typically occurs after the left subclavian artery. However, if situated before it, blood flow to the left arm is compromised and asynchronous or radial pulses of different "strength" may be detected (normal on the right arm, weak or delayed on the left), termed "radio-radial delay". In these cases, a difference between the normal radial pulse in the right arm and the delayed femoral pulse in the legs (either side) may be apparent, whilst no such delay would be appreciated with palpation of both delayed left arm and either femoral pulses. On the other hand, a coarctation occurring after the left subclavian artery will produce synchronous radial pulses, but "radio-femoral delay" will be present under palpation in either arm (both arm pulses are normal compared to the delayed leg pulses).