Hereditary hearing loss, also known as heriditary hearing impairment, or hereditary anacusis, is a partial or total inability to hear. An affected person may be described as hard of hearing. A deaf person has little to no hearing. Hearing loss may occur in one or both ears. In children hearing problems can affect the ability to learn language and in adults it can cause work related difficulties.
There are 4 types of hereditary hemochromatosis, types 1 through 4, depending on the gene that is mutated.
Type 1: Mutations of the HFE (human homeostatic iron regulator) gene
Type 2: (juvenile hemochromatosis): Mutations in the HJV (hemojuvelin BMP co-receptor) and HAMP (hepcidin antimicrobial peptide) genes
Type 3: Mutations in the TFR2 (transferrin receptor 2) gene
Type 4:(ferroportin disease): Mutations in the SLC40A1 (solute carrier family 40 member 1) gene
Other much rarer genetic disorders can cause hepatic iron overload, but the clinical picture is usually dominated by symptoms and signs due to failure of other organs (eg, anemia in hypotransferrinemia or atransferrinemia, or neurologic defects in aceruloplasminemia).
Although these types vary markedly in age of onset, clinical consequences of iron overload are the same in all types.
Type 1 is classic hereditary hemochromatosis, also termed HFE-related hemochromatosis. More than 80% of cases are caused by the homozygous C282Y mutation or the C282Y/H63D compound heterozygote mutation. Homozygous H63D mutations occur rarely and have the same phenotype as homozygous C282y cases. The disorder is autosomal recessive, with a homozygous frequency of 1:200 and a heterozygous frequency of 1:8 in people of northern European ancestry. The C282Y and H63D mutations are uncommon among people with African ancestry and rare among people with Asian ancestry. Of patients with clinical features of hemochromatosis, 83% are homozygous. However, for unknown reasons, phenotypic (clinical) disease is much less common than predicted by the frequency of the gene (ie, many homozygous people do not manifest the disorder).
Type 2 hereditary hemochromatosis (juvenile hemochromatosis) is a rare autosomal recessive disorder caused by mutations in the HJV gene that affect the transcription protein hemojuvelin, or mutations in the HAMP gene, which directly codes for hepcidin. It often manifests in adolescents.
Mutations in transferrin receptor 2 (TFR2) gene that codes for a protein that appears to control saturation of transferrin, can cause a rare autosomal recessive form of hemochromatosis.
Type 4 hereditary hemochromatosis (ferroportin disease) occurs largely in people of southern European ancestry. It results from an autosomal dominant mutation in the SLC40A1 gene and affects the ability of ferroportin to bind hepcidin.
In transferrin deficiency (hypotransferrinemia or atransferrinemia), absorbed iron that enters the portal system not bound to transferrin is deposited in the liver. Subsequent iron transfer to sites of red blood cell production is reduced because of transferrin deficiency.
In ceruloplasmin deficiency (aceruloplasminemia), lack of ferroxidase causes defective conversion of Fe2+ to Fe3+; such conversion is necessary for binding to transferrin. Defective transferrin binding impairs the movement of iron from intracellular stores to plasma transport, resulting in accumulation of iron in tissues.
Osler-Weber-Rendu syndrome. Alternative Names: Hereditary hemorrhagic telangiectasia Osler-Weber-Rendu syndrome is an inherited disorder of the blood vessels, which can cause excessive bleeding. The syndrome is also called hereditary hemorrhagic telangiectasia, or HHT.
Hyperuricemia and gout have long been known to run in families. As well as an apparently multifactorial genetic component to classic gout itself, 2 rather unusual sex-linked single-gene disorders of purine biosynthesis or recycling have been defined: deficiency of the enzyme hypoxanthine-guaninephosphoribosyl transferase (HPRT), and overactivity of PPriboseP synthase. Both result in overproduction of urate, hyperuricemia, and secondary overexcretion that may lead to acute or chronic renal damage. Familial juvenile hyperuricemic nephropathy (FJHN) and autosomal-dominant medullary cystic kidney disease (ADMCKD) are more common but less well-defined hyperuricemic conditions resulting from a decrease in the fractional excretion of filtered urate, with normal urate production. Although having features in common, ADMCKD is distinguished in particular by the presence of medullary cysts. One major group of both disorders is associated with mutations in the gene for uromodulin, but this accounts for only about one third of cases, and genetic heterogeneity is present. Whether the genes involved in these latter disorders contribute to the polygenic hyperuricemia and urate underexcretion of classic gout remains unexplored.
Hereditary koilonychia: An inherited anomaly where the nails are flattened or concave-shaped rather than the normal curved shape.
Hereditary macrothrombocytopenia: A rare inherited blood disorder where the blood platelets are abnormally large. Blood platelets are involved in the blood clotting process but patients with the condition often have no symptoms or suffer mild bleeding problems.
Autosomal recessive congenital methemoglobinemia is an inherited condition that affects the normal function of hemoglobulin (Hemoglobin carries oxygen to cells and tissues throughout the body). Methemoglobinemia, occurs when red blood cells (RBCs) contain methemoglobin at levels higher than 1%. Methemoglobin results from the presence of iron in the ferric form instead of the usual ferrous form. This results in a decreased availability of oxygen to the tissues, leading to a bluish appearance of the skin, lips, and nails (cyanosis).
There are four types of hereditary methemoglobinemias that are secondary to deficiency of NADH cytochrome b5 reductase, which is encoded by the CYB5R3gene. All of them are autosomal recessive disorders. Heterozygotes have 50% enzyme activity and no cyanosis; homozygotes that have elevated methemoglobin levels above 1.5% have clinical cyanosis. The four types are as follows:
Hereditary multiple exostoses (HME or MHE), also known as Diaphyseal aclasis, is a rare medical condition in which multiple bony spurs or lumps (also known as exostoses, or osteochondromas) develop on the bones of a child. HME is synonymous with Multiple hereditary exostoses and Multiple osteochondromatosis, which is the preferred term used by the World Health Organization.
Hereditary myopathy with intranuclear filamentous, aka Inclusion body myositis (IBM) is one of a group of muscle diseases known as inflammatory myopathies, which are characterized by chronic muscle inflammation accompanied by muscle weakness. It is a slowly progressive disease, which causes a gradual deterioration of muscles that become thin and weak over the years. Most limb muscles can be affected. In particular the quadriceps (the thigh muscles which extend the knee joint), and forearm muscles that flex the wrists and fingers are commonly weak. Accordingly, patients often notice difficulty with stairs, getting out of a chair and a poor grip. Swallowing muscles are affected in some patients, but the disease typically does not affect muscles of the heart, eye, gut or bladder. It also does not affect the function of the brain or sensation, and speech is rarely affected. In general patients do not die of the disease, but most meet with some degree of disability as the disease progresses. The disease itself is painless. However, weakened muscles can predispose to injuries affecting bones, joints and soft tissues.
There are two types - sporadic inclusion body myositis (sIBM) and hereditary inclusion body myositis (hIBM)
In sIBM, two processes, one autoimmune and the other degenerative, appear to occur in the muscle cells in parallel. It usually occurs in middle to late life and is more common in men than women.
hIBM lacks some of the inflammatory characteristics of sporadic IBM. The disease develops in young adults and is caused by a wide range of genetic defects that can be passed between generations. Generally, these defects cause neuromuscular disorders characterized by muscle weakness. hIBM comprise both autosomal recessive and autosomal dominant muscle disorders that have a variable expression (phenotype) in individual patients
Sources: Wikipedia, The Myositis Association; Medpedia; Muscular Dystrophy Campaign
Hereditary nodular heterotopia: A rare inherited disorder where a part of the brain tissue is misplaced during development.
Hereditary non-spherocytic hemolytic anemia: A group of genetic blood disorders where red blood cells are prematurely destroyed resulting in anemia if they are not replaced fast enough. The blood cells are destroyed because they have abnormally weak membranes which gives them an irregular shape rather than normal doughnut shape.
Hereditary non-polyposis colorectal cancer (also known as HNPCC, Lynch syndrome, Familial non-polyposis colon cancer) is an inherited genetic condition, which accounts for 2-7% of all colorectal cancers.
HNPCC is divided into two types, type 1 (also known as Lynch syndrome I or familial colon cancer), where tumors localize exclusively in the colon and type 2 (Lynch syndrome II), associated with other cancers of the gastrointestinal or reproductive system (stomach, endometrium, ovary, and urinary tract).
Source:
Müller A, Fishel R. Mismatch repair and the hereditary non-polyposis colorectal cancer syndrome (HNPCC). Cancer Invest. 2002;20(1):102-9.
University of California San Francisco (UCSF) Medical Center
Hereditary pancreatitis: A rare inherited condition involving recurring bouts of pancreatitis (inflammation of the pancreas) often leading to chronic pancreatitis due to scarring of the pancreas.
Acetazolamide-responsive, hereditary, paroxysmal, cerebellar ataxia (medical condition): A rare genetic disorder characterized by episodes of incoordination and unsteadiness as well as nystagmus (rapid, involuntary eye movements). Stress, exertion, alcohol and coffee may trigger the episodes which can last from hours to days. Type 2 is caused by a defect in the calcium ion gene on chromosome 19p13. Acetazolamide-responsive, hereditary, paroxysmal, cerebellar ataxia: Another name for Episodic ataxia, type 2 (or close medical condition association). Episodic ataxia, type 2: A rare genetic disorder characterized by episodes of incoordination and unsteadiness as well as nystagmus (rapid, involuntary eye movements). Stress, exertion, alcohol and coffee may trigger the episodes which can last from hours to days. Type 2 is caused by a defect in the calcium ion gene on chromosome 19p13.
Hereditary peripheral nervous disorder: A group of inherited disorders affecting the peripheral nerves (nerves other than the brain and spinal cord). The motor, sensory and/or autonomic nerves may be affected. Examples of such conditions includes Dejerine-Sottas disease and Charcot-Marie-Tooth disease.
Hereditary primary Fanconi disease: A rare inherited disorder characterized by defective reabsorption of various substances such as phosphate, potassium, amino acids and glucose which manifests as a wide range of abnormalities and problems.
Hereditary sensory neuropathy type II (HSN2) is a rare genetic disorder that usually begins in childhood by affecting the nerves that serve the lower arms and hands and the lower legs and feet (the peripheral nerves). Symptoms start with inflamed fingers or toes especially around the nails. Infection is common and worsens as ulcers (open sores) form on the fingers and on the soles of the feet. The loss of sensation in both hands and feet often leads to neglect of the wounds. This can become serious, even leading to amputation in extreme cases, so it is important to care for any such wounds.
Hereditary sensory and autonomic neuropathy type 3, also called familial dysautonomia, is a genetic disorder that affects the development and survival of certain nerve cells. The disorder disturbs cells in the autonomic nervous system, which controls involuntary actions such as digestion, breathing, production of tears, and the regulation of blood pressure and body temperature. It also affects the sensory nervous system, which controls activities related to the senses, such as taste and the perception of pain, heat, and cold. Familial dysautonomia is also called hereditary sensory and autonomic neuropathy, type III.
Hereditary sensory and autonomic neuropathy type 4 (HSAN 4) - also or more commonly known as Congenital insensitivity to pain with anhidrosis (CIPA) - has two characteristic features: the inability to feel pain and temperature, and decreased or absent sweating (anhidrosis). The signs and symptoms of CIPA appear early, usually at birth or during infancy, but with careful medical attention, affected individuals can live into adulthood.
The hereditary sensory neuropathies (HSN) include 4-6 similar but distinct inherited degenerative disorders of the nervous system (neurodegenerative) that frequently progress to loss of feeling, especially in the hands and feet. Some types of HSN are related to or identical with some forms of Charcot-Marie-Tooth disorder, and others are related to or identical with familial dysautonomia (Riley-Day syndrome). The classification of the HSNs is complicated, and the experts do not always agree on it. Hereditary sensory neuropathy type II (HSN2) is a rare genetic disorder that usually begins in childhood by affecting the nerves that serve the lower arms and hands and the lower legs and feet (the peripheral nerves). Symptoms start with inflamed fingers or toes especially around the nails. Infection is common and worsens as ulcers (open sores) form on the fingers and on the soles of the feet. The loss of sensation in both hands and feet often leads to neglect of the wounds. This can become serious, even leading to amputation in extreme cases, so it is important to care for any such wounds. The disorder affects many of the body’s systems, is characterized by early onset (infancy or early childhood) and is transmitted genetically as an autosomal recessive trait.
A rare inherited progressive condition where the muscles of the arms, legs and face become increasingly weak and stiff due to damage to nerve cells that control muscle movement. The legs are affected first and then the arms and face - the symptoms ascend up the body. This condition involves mutations in the same gene and overlapping symptoms with juvenile primary lateral sclerosis but the difference is that primary lateral sclerosis only involves degeneration of the upper motor neurons whereas infantile-onset spastic paralysis is more severe and involves degeneration of upper and lower motor neurons
Hereditary spastic paraplegia (HSP), is a group of inherited diseases whose main feature is progressive stiffness and contraction (spasticity) in the lower limbs,as a result of damage to or dysfunction of the nerves.
HSP is not a form of cerebral palsy even though it physically may appear and behave much the same as, for example, spastic diplegia. The origins of HSP are entirely separate phenomena from cerebral palsy. Despite this, some of the same anti-spasticity medications used in spastic cerebral palsy are sometimes used to try to treat HSP symptomatology.
The condition sometimes also affects the optic nerve and retina of the eye, causes cataracts, ataxia (lack of muscle coordination), epilepsy, cognitive impairment, peripheral neuropathy, and deafness. HSP is caused by defects in the mechanisms that transport proteins and other substances through the cell. Long nerves are affected because they have to transport cellular material through long distances, and are particularly sensitive to defects of cellular transport.
Hereditary spastic paraplegia was first described in 1883 by Adolph Strümpell, a German neurologist, and was later described more extensively in 1888 by Maurice Lorrain, a French physician.
An inherited blood disorder where a metabolic defect causes defects in the red blood cells membranes which leads to their characteristic spherical shape (normal cells are doughnut shaped) and premature destruction
Hereditary spherocytosis is a rare genetic condition characterized by a defect of the red blood cell membrane. People with this condition typically experience a shortage of red blood cells (anemia), yellowing of the eyes and skin (jaundice), and an enlarged spleen (splenomegaly). Most newborns with hereditary spherocytosis have severe anemia, although it improves after the first year of life. Splenomegaly can occur anytime from early childhood to adulthood. About half of affected individuals develop hard deposits in the gallbladder called gallstones, which typically occur from late childhood to mid-adulthood.
Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy) is a rare disease due to mutations in the gene encoding transthyretin (TTR) and characterized by multisystem extracellular deposition of amyloid, leading to dysfunction of different organs and tissues.
Hereditary sensory neuropathy Type I (HSN1) is a rare genetic disorder characterized by the loss of sensation (sensory loss), especially in the feet and legs and, less severely, in the hands and forearms. The sensory loss is due to abnormal functioning of the sensory nerves that control responses to pain and temperature and may also affect the autonomic nervous system that controls other involuntary or automatic body processes.
Hereditary sensory and autonomic neuropathy, type 2 (HSAN2) is an inherited disorder characterized by profound and universal sensory loss involving large and small fiber nerves, and marked hypotonia. The exact prevalence is unknown, but is estimated as very low (less than 50 cases reported). HSAN2 presents in infancy or early childhood and is non-progressive. There is no sex preference or particular ethnic preponderance, and to date there is no increased incidence of consanguinity.
Hereditary stomatocytosis and hereditary xerocytosis are rare, genetically distinct, autosomal dominant diseases of red blood cell sodium and potassium permeability. Hereditary cryohydrocytosis is a subtype of hereditary stomatocytosis. All three present with hemolysis and anemia, which can vary from mild to severe. The key signs and symptoms are those of all hemolytic anemias: jaundice, pallor, fatigue, splenomegaly, gallbladder disease, and susceptibility to an aplastic crisis following infection with parvovirus B19. The diseases begin at birth, but especially in the case of hereditary xerocytosis and hereditary cryohydrocytosis, may be mild enough to go undiscovered for years.