Cantú syndrome is a rare condition characterized by excess hair growth (hypertrichosis), a distinctive facial appearance, heart defects, and several other abnormalities. The features of the disorder vary among affected individuals.

People with Cantú syndrome have thick scalp hair that extends onto the forehead and grows down onto the cheeks in front of the ears. They also have increased body hair, especially on the back, arms, and legs. Most affected individuals have a large head (macrocephaly) and distinctive facial features that are described as "coarse." These include a broad nasal bridge, skin folds covering the inner corner of the eyes (epicanthal folds), and a wide mouth with full lips. As affected individuals get older, the face lengthens, the chin becomes more prominent, and the eyes become deep-set.

Many infants with Cantú syndrome are born with a heart defect such as an enlarged heart (cardiomegaly) or patent ductus arteriosus (PDA). The ductus arteriosus is a connection between two major arteries, the aorta and the pulmonary artery. This connection is open during fetal development and normally closes shortly after birth. However, the ductus arteriosus remains open, or patent, in babies with PDA. Other heart problems have also been found in people with Cantú syndrome, including an abnormal buildup of fluid around the heart (pericardial effusion) and high blood pressure in the blood vessels that carry blood from the heart to the lungs (pulmonary hypertension).

Additional features of this condition include distinctive skeletal abnormalities, a large body size (macrosomia) at birth, a reduced amount of fat under the skin (subcutaneous fat) beginning in childhood, deep horizontal creases in the palms of the hands and soles of the feet, and an increased susceptibility to respiratory infections. Other signs and symptoms that have been reported include abnormal swelling in the body's tissues (lymphedema), side-to-side curvature of the spine (scoliosis), and reduced bone density (osteopenia). Some affected children have weak muscle tone (hypotonia) that delays the development of motor skills such as sitting, standing, and walking. Most have mildly delayed speech, and some affected children have mild intellectual disability or learning problems.

Cantú syndrome results from mutations in the ABCC9 gene. This gene provides instructions for making one part (subunit) of a channel that transports charged potassium atoms (potassium ions) across cell membranes. Mutations in the ABCC9 gene alter the structure of the potassium channel, which causes the channel to open when it should be closed. It is unknown how this problem with potassium channel function leads to excess hair growth, heart defects, and the other features of Cantú syndrome.

Normal Function

The ABCC9 gene provides instructions for making the sulfonylurea receptor 2 (SUR2) protein. This protein forms one part (subunit) of a channel that transports charged atoms of potassium (potassium ions) across cell membranes. Each of these channels consists of eight subunits: four SUR2 proteins and four proteins produced from either the KCNJ8 or KCNJ11 gene. The SUR2 subunits regulate the activity of the channel, determining whether it is open or closed.

Channels made with the SUR2 protein are known as ATP-sensitive potassium (K-ATP) channels. The channels open and close in response to the amount of ATP, the cell's main energy source, inside the cell. The resulting transport of potassium ions is part of a complex network of signals that relay chemical messages into and out of cells.

Although K-ATP channels are present in cells and tissues throughout the body, the highest levels of SUR2-containing channels are found in skeletal and heart (cardiac) muscle. These channels indirectly help regulate the concentration of calcium ions in cells. This regulation is essential for normal heart function. The function of these channels in other tissues is unclear.

Health Conditions Related to Genetic Changes

Cantú syndrome

At least 14 mutations in the ABCC9 gene have been found to cause Cantú syndrome, a rare condition characterized by excess hair growth (hypertrichosis), a distinctive facial appearance, and heart defects. Each of the mutations changes a single protein building block (amino acid) in the SUR2 protein. These changes likely alter the structure of the protein and its ability to regulate the activity of K-ATP channels. Studies suggest that the abnormal channels are open when they should be closed. However, it is unknown how this problem with potassium channel function leads to excess hair growth, heart defects, and the other features of Cantú syndrome.

Familial atrial fibrillation

MedlinePlus Genetics provides information about Familial atrial fibrillation

Familial dilated cardiomyopathy

MedlinePlus Genetics provides information about Familial dilated cardiomyopathy

Other disorders

At least two mutations in the ABCC9 gene have been identified in people with dilated cardiomyopathy, a form of heart disease that enlarges and weakens the cardiac muscle, preventing the heart from pumping blood efficiently. Signs and symptoms of this condition can include an irregular heartbeat (arrhythmia), shortness of breath, extreme tiredness (fatigue), and swelling of the legs and feet. Research suggests that each mutation changes the structure of the SUR2 protein and disrupts the regulation of the K-ATP channel. Although K-ATP channels appear to play an important role in cardiac muscle, little is known about how malfunctioning channels are related to dilated cardiomyopathy.

Other Names for This Gene

• ABC37
• ABCC9_HUMAN
• ATFB12
• ATP-binding cassette sub-family C member 9
• ATP-binding cassette sub-family C member 9 isoform SUR2A
• ATP-binding cassette sub-family C member 9 isoform SUR2B
• ATP-binding cassette transporter sub-family C member 9
• ATP-binding cassette, sub-family C (CFTR/MRP), member 9
• CANTU
• CMD1O
• sulfonylurea receptor 2
• SUR2

Genomic Location

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered ABCC9 gene in each cell is sufficient to cause the disorder.

Most cases result from new mutations in the gene and occur in people with no history of the disorder in their family. In a few reported cases, an affected person has inherited the mutation from one affected parent.

Cantú syndrome is a rare condition. About three dozen affected individuals have been reported in the medical literature.