Genetic diseases or disorders are caused due to abnormalities in the genetic makeup of an individual. Such abnormalities can be caused by a minuscule, major variation or mutation in single or multiple genes, chromosomal aberrations, and rarely due to mutations in the non-chromosomal DNA of mitochondria. Genetic diseases or disorders may or may not be inheritable. They can be recessive or dominant in nature.
A rare disease in one part of the world may not be rare in another. In the United States, the criteria for rare diseases is defined in the Rare Diseases Act of 2002. It defines such diseases strictly according to its prevalence, specifically
There are about 6000 known genetic disorders many of which are degenerative, debilitating, and often fatal. In this article, let's know about some rarer forms of genetic diseases and disorders.
Aicardi syndrome is a very rare genetic disorder characterized by underdeveloped or absence of the corpus callosum, the structure separating the left and right half of the brain. It is found to affect only girls as it is believed to be caused due to a defect in the X chromosome. It affects 1 in 100,000 to 150,000 individuals in the United States. Babies born with this disorder seem normal till the age of 3 to 5 months and then start showing some key symptoms of this disorder.
Symptoms: They include retinal abnormalities and infantile spasms resulting in seizures. Individuals affected by this disease have serious developmental issues.
Treatment: There is no cure for this disorder. Treatment generally involves management of seizures and supporting the affected individuals through the delay in development.
Alagille syndrome is a rare genetic disorder that affects the liver, kidney, heart, and other organs of the body. Symptoms related to this syndrome are usually noticed in the early years of life. It affects around 1 in 70,000 newborns. It is inherited as an autosomal dominant trait, and the severity of symptoms may vary from individual to individual. Liver malfunctioning is caused by abnormalities in the bile duct (like less in number or absent, narrow, or malformed), resulting in bile accumulation in the liver and thus damaging it.
Symptoms: Symptoms include yellowish tinge on the skin and the whites of the eyes, accumulation of cholesterol beneath the skin, itching, etc. Individuals suffering from this disorder also face many heart problems. They have distinguishable facial features -- prominent forehead, pointed chin, and deep-set eyes.
Treatment: There is no cure for this syndrome; however, corrective surgery aimed at the functioning of heart, liver, and kidney helps to some extent.
Alkaptonuria, also known as black urine disease, is caused due to disorder in the tyrosine metabolism of the body. It affects about 1 in 250,000 to 1 million people worldwide. It is an autosomal recessive condition characterized by accumulation of alkapton or homogentisic acid (toxic tyrosine byproduct) in the blood, which is excreted in the urine. Urine of such patients becomes black when exposed to air. Presence of excess alkapton may result in osteoarthritis, heart disease, kidney stones, and prostate stones in men.
Symptoms: Some of the symptoms of alkaptonuria include darkened skin and pigmented sclera (white part of eye).
Treatment: No specific treatment has been established; however, it has been observed that consuming foods rich in vitamin C helps. It is also advisable to avoid diets rich in tyrosine and phenylalanine.
Alström syndrome is a rare autosomal recessive disorder causing multiple organ dysfunction. It is one of the rarest-known genetic diseases with only around 500 cases known in medical history.
Symptoms: Indications include childhood obesity, sensorineural hearing loss, and vision impairment. It can also lead to hyperinsulinemia, hypertriglyceridemia, early onset of diabetes 2, and deafness. This syndrome can also cause several life-threatening medical complications involving liver, heart, lungs, etc.
Treatment: There is no cure for this syndrome; however, medication can be provided to cure specific symptoms of the syndrome.
Apert syndrome is a rare genetic disorder that is apparent at birth. It results in distortion in the shape of skull and face, and sometimes, the hands and feet are webbed. It affects 1 in 65,000 to 88,000 newborns. In people affected by this syndrome, the bones of the skull fuse prematurely, a condition called craniosynostosis, while the brain keeps developing inside the abnormal skull causing pressure on the skull and face, resulting in its distortion.
Symptoms: It also results in poor intellectual development of the individual, hearing loss, frequent ear and sinus infections, and short stature. In most cases, the syndrome results due to random gene mutation while in some rare instances, it is inherited as an autosomal dominant trait.
Treatment: There is no cure for this disorder but surgery can, to some extent, cure some of its symptoms.
Batten disease is a rare autosomal recessive disorder that chiefly affects the nervous system and begins in the childhood stage. It is estimated to be occurring in every 2 to 4 of every 100,000 individuals. Batten disease is characterized by a buildup of pigments called lipofuscins in the body cells.
Symptoms: Symptoms usually appear between 5 to 10 years of age when a normal child suddenly starts having vision problems and seizures. Overtime, the symptoms worsen resulting in loss of motor ability, mental retardation, loss of sight, etc.
Treatment: There is no cure for this condition, and it is generally fatal by the age of 20.
Bardet-Biedl syndrome is a rare genetic disorder affecting multiple organs. It affects 1 in 140,000 to 1 in 160,000 newborns. The signs and symptoms may differ among individuals who are affected by syndrome, even among family members.
Symptoms: It is characterized by vision impairment, obesity, kidney anomalies, development issues, extra finger and toes, impaired motor skills, etc. This disorder is recessive in nature.
Treatment: There is no cure for the disorder, and usually treatment is concentrated on specific symptoms.
Camurati-Engelmann disease is a kind of bone dysplasia. It is a rare autosomal dominant genetic disorder. Only 200 cases of the disease have been reported worldwide so far.
Symptoms: It is characterized by thickened bones resulting in chronic pain. The skull bones also thicken resulting in pressure on the brain, leading to various neurological problems. Individuals suffering from it also complain of increased fatigue, weakness, headache, and muscle spasms.
Treatment: There is no cure for this condition but it can be partially treated. Anti-inflammatory and immunosuppressive agents, like glucocorticosteroids have proved to be helpful in some cases. Alternative therapies, like massage and heat therapy in conjunction with medication are also advisable.
Carpenter syndrome is a rare congenital disorder characterized by malformed head, face, fingers, and toes due to premature fusion of bones. It is an autosomal recessive disorder with around 100 documented cases known till date. It is estimated to affect 1 in 1000,000 individuals.
Symptoms: Key symptoms include oddly-shaped head, fused digits, obesity, short stature, and reduced mental ability. 50% of the babies with this disorder have a heart defect which complicates the situation.
Treatment: Treatment generally consists of a number of staged surgeries to correct the malformation of bones in the early stages of life. This condition is similar to Apert Syndrome and Pfeiffer Syndrome.
Familial Idiopathic Basal Ganglia Calcification
Formerly known as Fahr's syndrome, it is a rare genetically dominant disorder. It is characterized by abnormal deposits of calcium in the basal ganglia and cerebral cortex. These are areas of brain control movement.
Symptoms: Key symptoms are clumsiness, fatigue, unsteady posture, muscle cramping, uncontrolled movement, and dementia. Individuals can be affected by this syndrome at any time of their life; however, it is more prevalent in the age group of 40-50 years. Only 60 families are known to be affected by this syndrome in medical literature.
Treatment: There is no cure for this condition. Treatment is generally symptomatic.
Hereditary angioedema, also known as Quincke's disease, is caused due to abnormalities in the function of a protein called C1 inhibitor. Mutations within the C1-inhibitor gene (C1NH) result in HAE. It affects the blood vessels, resulting in immune system problems. It is estimated to occur in 1 in 50,000 individuals.
Symptoms: Common symptoms of hereditary angioedema include swelling of the arms, legs, eyes, and throat, abdominal pain, and airway blockage.
Treatment: Treatment is usually done by following medication, hormonal treatment, and administration of painkillers.
Huntington's disease is an autosomal dominant genetic disorder and is more prevalent in the mid-adult life. With time, the symptoms aggravate and the affected individual needs full-time care. This condition affects 1 in 10,000 in United States. Life expectancy after the onset of the disease is 15-25 years.
Symptoms: Indicants include involuntary movements, loss of motor abilities, cognitive difficulties, and emotional problems.
Treatment: There is no cure, but medication can relieve specific symptoms associated with the disorder.
Joubert's syndrome is a rare autosomal recessive genetic disorder of the brain. It affects around 1 in 80,000 to 100,000 individuals. This disorder is characterized by an underdeveloped or absent cerebellar vermis and a malformed brain stem. This part of the brain controls coordination and balance.
Symptoms: Some key symptoms of this disorder are lack of muscle control, abnormal breathing pattern, jerky eye movement, intellectual disability, and physical deformities, such as cleft lip, extra finger, and toes. The severity of the symptoms varies from individual to individual.
Treatment: There is no cure for the disease but treatment for symptoms, like breathing difficulty can be meted out.
Kartagener's syndrome is a genetic disorder that causes chronic lung disease. About 1 in 30,000 people are estimated to be affected with this syndrome (although the number could be as high as 1 in 15,000). It is caused due to a defect in the action of the cilia lining the respiratory tract, which results in abnormal ciliary motion. Patients affected with this syndrome are found to have defects in genes DNAH5 and DNAI1.
Symptoms: It is characterized by difficulty in breathing, wheezing, chronic cough, sinusitis, bronchitis, and infertility.
Treatment: Treatment for this syndrome is done by following medications, chest physiotherapy, and sometimes, surgical intervention is needed.
Krabbe disease is caused due to disorder in the myelin sheath of the peripheral and central nervous system. It leads to destruction of the brain cells. About 1 in 100,000 births are affected with this genetic disorder. Usually, children with Krabbe disease die before the age of 2.
Symptoms: This disease is characterized by vomiting, seizures, mental retardation, deafness, and blindness.
Treatment: Bone marrow transplantation has shown to be helpful in some cases of this disease. Recent studies have found out that newborn babies with Krabbe disease can be treated with the help of stem cells from umbilical cord blood storage.
Meckel syndrome is an extremely rare, fatal genetic disorder. It is inherited in an autosomal recessive fashion and affects around 1 in 13,250 to 140,000 people worldwide. Due to its severe symptoms, individuals usually die during birth or shortly after birth. It is more common in Belgium and Finland with around 1 in 3000-9000 people being affected by it.
Symptoms: It has severe signs and symptoms including malformed central nervous system, numerous fluid-filled cysts in the kidney, defects in the lungs, liver, polydactyly.
Treatment: Cardiac repair, or neurosurgical intervention for encephalocele may be recommended.
Mucopolysaccharidosis VI is a genetic disease that affects about 1 in 300,000 births. It is caused due to the deficiency of N-acetylgalactosamine 4-sulfatase (arylsulfatase B) activity that is responsible for catabolism of complex carbohydrates (polysaccharides). This results in accumulation of dermatan sulfate in some of the organs, such as skeleton, lung, heart valves, spleen, and liver.
Symptoms: Symptoms include short stature, mental retardation, respiratory diseases, deafness, and blindness.
Treatment: Treatment is done by following enzyme replacement therapy along with regular medical care.
Pfeiffer syndrome is associated with mutation of fibroblast growth factor receptor which is important for normal bone development. It is a rare autosomal dominant genetic disorder affecting 1 in 100,000 individuals. It is characterized by abnormal fusion of the skull bones resulting in a malformed head and face. It can also affect the bones in the feet and hands.
Symptoms: Visible symptoms of this syndrome are unusually broad forehead, bulging eyes, beaked nose, short broad thumbs and toes. In certain cases, webbing of the digits is also seen. Individual suffering from this syndrome also faces hearing loss and dental issues.
Treatment: Staged craniofacial surgeries are usually performed in the early months of life to rectify the deformation in bones.
Progeria is a rare genetic condition affecting around 1 in 8000,000 live births. It is a genetic condition caused as a result of a new mutation in the gene and is generally not inherited. It causes rapid aging in children, and as a result, individuals affected by this disease die by the age of 13 to 20.
Symptoms: Key symptoms of progeria are growth problems in the first year of life, wrinkled small face, large head, loss of hair, eyebrows, and eyelashes, poor eyesight, and reduced motor skills. A genetic test for LMNA mutation can confirm if an individual has progeria.
Treatment: There is no cure for this disease. All treatment options offered are generally supportive and symptom-specific.
Rett syndrome is a rare genetic developmental disorder of the nervous system. It is an autsomal dominant X-linked disorder and is more prevalent in females than in males. It affects 1 out of 10,000 individuals. Symptoms generally surface after 6-18 months of life.Symptoms
: They include breathing problems, sensory problem, unsteady gait, learning disabilities, seizures, social awkwardness, or unresponsiveness. The symptoms are often misinterpreted with that of autism and cerebral palsy.Treatment
: There is no cure for this syndrome; however, research in this area is ongoing.
Ribose-5-phosphate Isomerase Deficiency
The deficiency arises due to a mutation in the enzyme ribose 5-phosphate isomerase, which plays a vital role in the pentose phosphate pathway. With only a single diagnosed case, this disorder is considered to be the rarest. MRI screening showed higly elevated levels of arabitol and ribitol, indicating an inborn error in polyol metabolism. The patient exhibited symptoms like white matter disease and neuropathy of unknown origin. The cause of the condition is yet to be fully understood. There are several theories doing the rounds, but this deficiency is still under study.
Sandhoff disease is a rare genetic lipid storage disorder that destroys the nerve cells in the brain and spinal cord. It is caused due to the deficiency of functional beta-hexosaminidases A & B, which lead to the deposition of certain lipids in brain and other organs of the body. This autosomal disorder affects 1 in 300,000 individuals. Of the 3 types of this syndrome, classic infantile is the most lethal.
Symptoms: Affected babies exhibit muscle weakness, loss of motor skills, suffer hearing loss, paralysis, vision loss, red cherry spots, intellectual disability, and usually survive till the age of 3-4 years.
Treatment: Treatment for this condition is generally supportive.
Tuberous sclerosis was formerly known as Bourneville's disease. It is a rare genetic disorder and affects about 1 in 10,000 people throughout the world. About 80% of the cases are due to mutations in two specific genetic loci -- TSC1 and TSC2. Tuberous sclerosis is caused due to growth of tuber-like tumors in brain, lungs, heart and kidneys.
Symptoms: Common symptoms include skin lesions in the nose and cheek area, periungual fibroma, epileptic seizures, behavioral problems, lung and kidney diseases and mental retardation.
Treatment: Symptoms of epileptic seizures can be treated by surgically removing the tubers that are responsible for epilepsy. Studies are being conducted to find out drug therapies for this disease.
Wolman disease is rare genetic disorder affecting around 1 in 35,000 individuals. It is an autosomal recessive disorder caused by the deficiency of lysosomal acid lipase (LAL). LAL is an enzyme necessary to breakdown certain lipids in the cells. In individuals suffering from this condition, harmful quantity of lipids accumulate in the liver, spleen, lymph nodes, bone marrow, and other parts of the body. The symptoms are generally evident in the first few weeks of life.
Symptoms: They include feeding issues, constant vomiting, diarrhea, enlarged liver and spleen, poor weight gain, etc.
Treatment: There is no cure for this condition; however, there are treatments that are symptomatic and supportive.
Zimmermann-Laband Syndrome (ZLS)
With only 44 known cases, Zimmermann-Laband Syndrome is a very rare congenital, autosomal dominant disorder.
Symptoms: It is characterized by gingival fibromatosis (large gums), absent or underdeveloped nails of terminal phalanges of hand and feet, abnormal nose and ear, and rough facial appearance.
Treatment: Treatment for this syndrome is usually symptomatic and supportive.
Genetic diseases and disorders are a major challenge for medical researchers all over the world. Researches on cloning of genes, gene therapy, and suppression of genes responsible for causing genetic diseases and enzyme replacement are still on to find ways to treat rare genetic diseases and disorders.