By D. Mufassa. Central Pennsylvania College.
Other manifestations Problems with the structure and function of kidneys Treatment and management have been noted with an occurrence of 40-70% cheap vardenafil 20mg mastercard. Most often symptoms are mild order vardenafil 10mg without prescription, but renal disease has caused Liver transplantation is needed in 15-20% of mortality in severe cases. Other treatments depend on which of the other function have been noted in 16% of children. Most of features of the condition are present and the degree of these children were those with severe organ disease. Repair of heart defects is another surgical treat- Intracranial bleeding has also been noted with increased ment needed in some cases. Prognosis Prognosis for Alagille syndrome is quite variable Diagnosis and depends on the degree of liver, heart, and kidney dis- The diagnosis of Alagille syndrome is based on clin- ease and the presence of intracranial bleeding. Overall, ical features and can be made by the presence of liver survival rates are 72-85%. There is cur- sound of the liver can rule out other causes of liver dis- rently no method to determine which patients will reach ease and a liver biopsy can determine if there is a end-stage liver disease. However, this find- ing occurs in other conditions as well as Alagille syn- Resources drome, and the timing of the biopsy is important. Older BOOKS patients are more likely to have fewer bile ducts than Jones, Kenneth Lyons. The Metabolic and Molecular Bases of Hermansky-Pudlak syndrome (HPS)—A rare form Inherited Disease. Platelets—Small disc-shaped structures that circu- late in the blood stream and participate in blood Sonja Rene Eubanks clotting. Retina—The light-sensitive layer of tissue in the back of the eye that receives and transmits visual signals to the brain through the optic nerve. Strabismus—An improper muscle balance of the IAlbinism ocular muscles resulting in crossed or divergent Definition eyes. Albinism is an inherited condition that causes a lack of pigment in the hair, skin, or eyes. Types of albinism Description Ocular: A form of albinism that mainly affects the eyes. People with ocular albinism have some pigmenta- People with albinism typically have white or pale tion, but may have lighter skin, hair, and eye color than yellow hair, pale skin, and light blue or gray eyes. Scientists have identified five dif- their irises have little pigment, their eyes may appear ferent types of ocular albinism. This is because light is being reflected from the reddish part of the retina X-linked ocular: This type of albinism occurs mostly in the back of the eye. Their skin usually does not tan in males, who inherit the gene from their mothers. Some children may be born with Oculocutaneous: A type of albinism that affects the albinism, but develop some pigmentation as they grow hair, skin, and eyes. In albinism, the body does not produce enough of a Tyrosinase-negative oculocutaneous: Also known as pigment called melanin, which creates hair, skin, and eye Type 1A, this is the most severe form of albinism, color. People with this type of albinism have vision prob- some affect only the eyes, while others affect the skin and lems and sensitivity to sunlight.
For reasons yet unknown discount 10 mg vardenafil with amex, the severity in symptoms Types of CMT can also vary greatly discount 10mg vardenafil visa, even among members of the same family. CMT1A Although CMT has been described for many years, The most common type of CMT is called CMT1A. In most people who have CMT, the mutation that causes the condition is a duplica- The peripheral nerves tion (doubling) of the PMP22 gene. Instead of having two copies of the PMP22 gene (one on each chromosome), CMT affects the peripheral nerves, those groups of there are three copies. It is not known how this extra copy nerve cells carrying information to and from the spinal of the PMP22 gene causes the observed symptoms. A cord and decreases their ability to carry motor commands small percentage of people with CMT1A do not have a to muscles, especially those furthest from the spinal cord duplication of the PMP22 gene, but rather have a point located in the feet and hands. Therefore, people with CMT also have Hereditary neuropathy with liability to pressure sensory loss. This causes symptoms such as not being palsies (HNPP) able to tell if something is hot or cold or difficulties with balance. HNPP is a condition that is also caused by a muta- There are two parts of the nerve that can be affected tion in the PMP22 gene. A nerve can be likened to an electrical wire, in resulting in only one copy of the PMP22 gene instead of which the wire part is the axon of the nerve and the insu- two. People who have HNPP may have some of the signs lation surrounding it is the myelin sheath. However, they also have episodes where they myelin is to help messages travel very fast through the develop weakness and problems with sensation after nerves. CMT is usually classified depending on which compression of certain pressure points such as the elbows part of the nerve is affected. Often, these symptoms will resolve after a few with the myelin have CMT type 1 and people who have days or weeks, but sometimes they are permanent. CMT1B Specialized testing of the nerves, called nerve con- duction testing (NCV), can be performed to determine if Another type of CMT, called CMT1B, is caused by a person has CMT1 or CMT2. These tests measure the a mutation in a gene called myelin protein zero (MPZ) GALE ENCYCLOPEDIA OF GENETIC DISORDERS 219 located on chromosome 1. The job of this gene is to make Inheritance the layers of myelin stick together as they are wrapped around the axon. The mutations in this gene are point Autosomal dominant inheritance mutations because they involve a change (either deletion, CMT1A and 1B, HNPP, and all of the subtypes of substitution, or insertion) at one specific component of a CMT2 have autosomal dominant inheritance. In a dominant condi- tion, only one gene of a pair needs to have a mutation in Another type of CMT, called CMTX, is usually con- order for a person to have symptoms of the condition. This chance is the same for each pregnancy and the X chromosome and is called connexin 32 (Cx32). Since males only CMT2 have one X chromosome, they only have one copy of the Cx32 gene. Thus, when a male has a mutation in his There are at least five different genes that can cause Cx32 gene, he will have CMT. Therefore, CMT2 has subtypes A, B, C, D two X chromosomes and therefore have two copies of the and E. If they have a mutation in one copy of their the location of most of the CMT2 causing genes. Cx32 genes, they will only have mild to moderate symp- However, the specific genes and the mutations have not toms of CMT that may go unnoticed. Very recently, the gene for their normal copy of the Cx32 gene produces sufficient CMT2E has been found.