Generalized arterial calcification of infancy | |
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Other names | Idiopathic infantile arterial calcification (IIAC), arterial calcification of infancy, idiopathic arterial calcification of infancy (IACI), occlusive infantile arterial calcification, occlusive infantile arteriopathy [1] |
Specialty | Medical genetics |
Generalized arterial calcification of infancy (GACI) is an extremely rare [2] genetic disorder. It is caused by mutations in the ENPP1 gene in 75% of the subjects [3] or in mutations in the ABCC6 genes in 10% of patients. [4] However, sometimes individuals affected with GACI do not have mutations in the ENPP1 or ABCC6 gene and in those cases the cause of the disorder is unknown. [4]
The condition usually affects infants during the first 6 months of life. This condition is inherited as an autosomal recessive pattern. It is characterized by generalized calcification of the arterial internal elastic lamina, leading to rupture of the lamina and occlusive changes in the tunica intima with stenosis and decreased elasticity of the vessel wall. [5] Unfortunately, many infants die of vaso-occlusive disease, especially of the coronary arteries. [6]
There are 2 forms of GACI that can be indicated on a genetic test:
GACI Type 1 is caused by mutations in the ENPP1 gene. It is called ENPP1 Deficiency. Patients with the ENPP1 Deficiency are at risk of developing Autosomal Recessive Hypophosphatemic Rickets Type 2 (ARHR2). ARHR2 can cause weakening in the bones, pain in bones and joints bone deformities (knocked knees, bowed legs), dental problems, calcification of ligaments and short stature. With proper treatment the bones can be strengthened and side effects minimized. [7] [8] [9]
GACI Type 2 is caused by mutations in the ABCC6 gene. It is called ABCC6 Deficiency. As children affected by GACI due to ABCC6 Deficiency get older, they can develop characteristics similar to pseudoxanthoma elasticum (PXE). This condition affects the elastic tissue of the skin, the eye, cardiovascular and gastrointestinal systems. [7] [8] [9]
Clinical presentation is variable. First symptoms usually occur at birth but can take place in the first 6 months of life or in utero. [2]
Clinical Signs for GACI can include:
The condition results from an inactivating mutation in the ecto-nucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1 gene) or the ATP-binding C member 6 (ABBC6 gene), leading to decreased inorganic pyrophosphate (PPi). [7] This is a potent inhibitor of calcium deposition in the vessel wall. These mutations allow for unregulated calcium deposition within muscular arteries. The symptoms are caused by calcification of large and medium-sized arteries, including the aorta, coronary arteries, and renal arteries.[ citation needed ]
Recently, homozygous or compound heterozygous mutations for ENPP1 gene were reported as causative for the disorder. ENPP1 regulates extracellular inorganic pyrophosphate (PPi), a major inhibitor of extracellular matrix calcification. [16]
The critical period for babies affected by GACI is during the first 6 months after birth. This is due to calcium continuing to build up in the artery walls. If blood flow becomes restricted it can become life threatening. [7]
GACI affects males and females equally and occurs in populations all across the world. It is estimated to occur in approximately 1 out of every 391,000 births with the carrier rate being 1:312. Survival statistics vary greatly. [7]
Generalized arterial calcification of infancy should always be considered in infants and children presenting with hypertension, cardiac failure, or sudden death. [17] Plain radiography, [18] sonography [19] and MRI [20] can aid in the diagnosis. Postnatal gray-scale and color Doppler echocardiographic and sonographic examinations allowed noninvasive diagnosis, assessment of severity, and monitoring of progression. [21] Contrast-enhanced MR angiography with breath-hold and cardiac gating techniques can allow evaluation of the extent of the disease. [22]
In 2015, Demetrios Braddock, MD, PhD, a pathologist and professor from Yale University along with his team published an article in Nature Communications. [49] Their research revealed when mice with GACI were given a replacement version of the enzyme, it helped to reduce the calcifications and prevented the animals from dying. [49] [50] [51] This discovery has led to the development of Inozyme Pharma [51] [9] a biotechnology company developing new medicines to treat rare disorders of calcification including GACI. [52]
Cardiology is the study of the heart. Cardiology is a branch of medicine that deals with disorders of the heart and the cardiovascular system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease, and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists, a sub-specialty of internal medicine. Pediatric cardiologists are pediatricians who specialize in cardiology. Physicians who specialize in cardiac surgery are called cardiothoracic surgeons or cardiac surgeons, a specialty of general surgery.
Cyanosis is the change of body tissue color to a bluish-purple hue, as a result of decrease in the amount of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Cyanosis is apparent usually in the body tissues covered with thin skin, including the mucous membranes, lips, nail beds, and ear lobes. Some medications may cause discoloration such as medications containing amiodarone or silver. Furthermore, mongolian spots, large birthmarks, and the consumption of food products with blue or purple dyes can also result in the bluish skin tissue discoloration and may be mistaken for cyanosis. Appropriate physical examination and history taking is a crucial part to diagnose cyanosis. Management of cyanosis involves treating the main cause, as cyanosis isn’t a disease, it is a symptom.
Vascular surgery is a surgical subspecialty in which vascular diseases involving the arteries, veins, or lymphatic vessels, are managed by medical therapy, minimally-invasive catheter procedures and surgical reconstruction. The specialty evolved from general and cardiovascular surgery where it refined the management of just the vessels, no longer treating the heart or other organs. Modern vascular surgery includes open surgery techniques, endovascular techniques and medical management of vascular diseases - unlike the parent specialities. The vascular surgeon is trained in the diagnosis and management of diseases affecting all parts of the vascular system excluding the coronaries and intracranial vasculature. Vascular surgeons also are called to assist other physicians to carry out surgery near vessels, or to salvage vascular injuries that include hemorrhage control, dissection, occlusion or simply for safe exposure of vascular structures.
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Stenosis is the abnormal narrowing of a blood vessel or other tubular organ or structure such as foramina and canals. It is also sometimes called a stricture.
Coarctation of the aorta (CoA) is a congenital condition whereby the aorta is narrow, usually in the area where the ductus arteriosus inserts. The word coarctation means "pressing or drawing together; narrowing". Coarctations are most common in the aortic arch. The arch may be small in babies with coarctations. Other heart defects may also occur when coarctation is present, typically occurring on the left side of the heart. When a patient has a coarctation, the left ventricle has to work harder. Since the aorta is narrowed, the left ventricle must generate a much higher pressure than normal in order to force enough blood through the aorta to deliver blood to the lower part of the body. If the narrowing is severe enough, the left ventricle may not be strong enough to push blood through the coarctation, thus resulting in a lack of blood to the lower half of the body. Physiologically its complete form is manifested as interrupted aortic arch.
Kawasaki disease is a syndrome of unknown cause that results in a fever and mainly affects children under 5 years of age. It is a form of vasculitis, where medium-sized blood vessels become inflamed throughout the body. The fever typically lasts for more than five days and is not affected by usual medications. Other common symptoms include large lymph nodes in the neck, a rash in the genital area, lips, palms, or soles of the feet, and red eyes. Within three weeks of the onset, the skin from the hands and feet may peel, after which recovery typically occurs. The disease is the leading cause of acquired heart disease in children in developed countries, which include the formation of coronary artery aneurysms and myocarditis.
Calcification is the accumulation of calcium salts in a body tissue. It normally occurs in the formation of bone, but calcium can be deposited abnormally in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification. Calcification may also refer to the processes of normal mineral deposition in biological systems, such as the formation of stromatolites or mollusc shells.
Hypophosphatasia (; also called deficiency of alkaline phosphatase, phosphoethanolaminuria, or Rathbun's syndrome; sometimes abbreviated HPP) is a rare, and sometimes fatal, inherited metabolic bone disease. Clinical symptoms are heterogeneous, ranging from the rapidly fatal, perinatal variant, with profound skeletal hypomineralization, respiratory compromise or vitamin B6 dependent seizures to a milder, progressive osteomalacia later in life. Tissue non-specific alkaline phosphatase (TNSALP) deficiency in osteoblasts and chondrocytes impairs bone mineralization, leading to rickets or osteomalacia. The pathognomonic finding is subnormal serum activity of the TNSALP enzyme, which is caused by one of 388 genetic mutations identified to date, in the gene encoding TNSALP. Genetic inheritance is autosomal recessive for the perinatal and infantile forms but either autosomal recessive or autosomal dominant in the milder forms.
Pseudoxanthoma elasticum (PXE) is a genetic disease that causes mineralization of elastic fibers in some tissues. The most common problems arise in the skin and eyes, and later in blood vessels in the form of premature atherosclerosis. PXE is caused by autosomal recessive mutations in the ABCC6 gene on the short arm of chromosome 16 (16p13.1).
Fibromuscular dysplasia (FMD) is a non-atherosclerotic, non-inflammatory disease of the blood vessels that causes abnormal growth within the wall of an artery. FMD has been found in nearly every arterial bed in the body, although the most commonly affected are the renal and carotid arteries.
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Ectonucleotide pyrophosphatase/phosphodiesterase family member 1 is an enzyme that in humans is encoded by the ENPP1 gene.
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