{"id":1480,"date":"2020-08-07T00:54:39","date_gmt":"2020-08-07T00:54:39","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/genetic-diseases\/genetic-diseases-autosomal-recessive-diseases-ii\/"},"modified":"2020-08-07T01:01:33","modified_gmt":"2020-08-07T01:01:33","slug":"genetic-diseases-autosomal-recessive-diseases-ii","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/genetic-diseases\/genetic-diseases-autosomal-recessive-diseases-ii\/","title":{"rendered":"Genetic Diseases: Autosomal Recessive Diseases II"},"content":{"rendered":"<span class=\"block-heading\" id=\"header_1\">\n<h2 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Phenylketonuria(PKU)<\/h2>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<ul class=\"wp-block-list\"><li>Phenylketonuria is a <strong>monogenic<\/strong> inborn error of metabolism that is characterized by the presence of phenyl ketones in the urine.<\/li><li>It has different causes but the underlying problem is the excess amount of phenylalanine in the blood <strong>(Hyperphenylalaninemia)<\/strong>. This causes phenylalanine to accumulate in blood and body fluids. Eventually, it is metabolised to phenyl ketones that are excreted in the urine.<\/li><li>Hyperphenylalaninemia can affect the development of the nervous system in early childhood and this can lead to neurological problems later in life<\/li><li>There are 4 forms of PKU<\/li><\/ul>\n\n\n\n<ol class=\"wp-block-list\"><li>Classical PKU<\/li><li>Maternal PKU<\/li><li>Variant PKU<\/li><li>Diet resistant PKU<\/li><\/ol>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title3\">Classical PKU<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<ul class=\"wp-block-list\"><li>This is caused by a mutation in the enzyme <strong>Phenylalanine Hydroxylase(PAH)<\/strong>.<\/li><li>Lack of PAH activity causes phenylalanine to accumulate in the body because it is the enzyme responsible for conversion of Phenylalanine to Tyrosine<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title3\">Maternal PKU<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<ul class=\"wp-block-list\"><li>This is hyperphenylalaninemia of the newborn caused by untreated PKU of the mother(the excess phenylalanine can pass through the placenta to get to the baby).<\/li><li>It can lead to birth defects.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title3\">Variant PKU<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<ul class=\"wp-block-list\"><li>In this case, the mutant PAH enzyme has some activity and can metabolize phenylalanine.<\/li><li>There is a higher-than-normal phenylalanine concentration in the blood but not too high.<\/li><li>Most of them are compound heterozygotes<em>(details on compound heterozygotes are discussed in the Transmission Genetics: Deviations from Mendelian Genetics Course)<\/em>.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title3\">Diet resistant PKU<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<ul class=\"wp-block-list\"><li>This is PKU that is caused not by a defect in PAH, but a defect in the formation or recycling of<strong> Tetrahydrobiopterin(BH4)<\/strong> which is the cofactor of the PAH enzyme.<\/li><li>It will also lead to a decrease in the synthesis of neurotransmitters such as dopamine, serotonin, epinephrine and norepinephrine as BH4 is required for the synthesis of these neurotransmitters.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">PKU screening in newborns should be done within the first 2-3 days of life because early detection can lead to better treatment and prevent complications later on in life.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_6\">\n<h2 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Tay-Sachs Disease<\/h2>\n<\/span><span class=\"block-content\" id=\"contents_6\">\n\n\n<ul class=\"wp-block-list\"><li>This is a lysosomal storage disease.<\/li><li><strong>Lysosomal storage diseases<\/strong> are a group of metabolic disorders that arise from a defect in the ability of lysosomal hydrolases to break down and digest certain molecules.<\/li><li>Since the large molecules cannot be digested, they accumulate in the cell and eventually kill it.<\/li><li>Other lysosomal storage diseases are Hurler Syndrome, Hunter Syndrome and I-cell disease.<\/li><li>In Tay-Sachs disease, a sphingolipid known as <strong>GM2 ganglioside<\/strong> will accumulate inside the cells due to a defect in the enzyme <strong>Hexosaminidase A(HexA)<\/strong>.<\/li><li>It is very common in Ashkenazi Jewish populations and doesn&#8217;t appear until a few months after birth.<\/li><li>If untreated, it can cause blindness, neurological deterioration and eventually, death.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_7\">\n<h2 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Hurler Syndrome<\/h2>\n<\/span><span class=\"block-content\" id=\"contents_7\">\n\n\n<ul class=\"wp-block-list\"><li>This is a lysosomal storage disease.<\/li><li>In this disease, <strong>mucopolysaccharides or glycosaminoglycans<\/strong>&nbsp;will accumulate inside the cells due to a defect in the enzyme <strong>alpha-L-iduronidase<\/strong>.<\/li><li>It is one of the two <strong>mucopolysaccharidoses <\/strong>(because of accumulation of mucopolysaccharides). The other one is Hunter Syndrome.<\/li><li>It can cause skeletal abnormalities and short stature, mental retardation and other neurological problems and early death.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_8\">\n<h2 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">I-cell Disease<\/h2>\n<\/span><span class=\"block-content\" id=\"contents_8\">\n\n\n<ul class=\"wp-block-list\"><li>This is a lysosomal storage disease.<\/li><li>In this disease, unlike the others mentioned above, the enzymes are produced but they do not reach the cell.<\/li><li>For enzymes made in ribosomes to get to the lysosome, <strong>mannose-6-phosphate residues<\/strong> must be present on the enzymes because they need to be <strong>recognised by receptors<\/strong> on the lysosomes.<\/li><li>I-cell disease, also known as <strong>loss of glycosylation<\/strong>, is caused by a <strong>defect in the enzyme responsible for phosphorylation of the mannose residues<\/strong>.<\/li><li>It can cause skeletal abnormalities and short stature, mental retardation and other neurological problems and early death at 5-7 years.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_9\">\n<h2 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Alpha-1 antitrypsin deficiency<\/h2>\n<\/span><span class=\"block-content\" id=\"contents_9\">\n\n\n<ul class=\"wp-block-list\"><li>In this disease, <strong>Alpha 1 anti-trypsin<\/strong> is not produced.<\/li><li>Alpha 1 anti-trypsin is an inhibitor of serine proteases such as elastase.<\/li><li>Without the inhibitory activity of Alpha 1 anti-trypsin, overactivity of elastase can lead to emphysema as elastase destroys the alveolar walls.<\/li><li>Emphysema can also develop in healthy people who smoke. This is because the cigarette smoke oxidizes the methionine at the active site of Alpha 1 anti-trypsin and decreases its affinity for elastase.<\/li><\/ul>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h2 class=\"wp-block-heading\" class=\"wp-block-heading\">Phenylketonuria(PKU)<\/h2><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Classical PKU<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Maternal PKU<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Variant PKU<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Diet resistant PKU<\/h4><h2 class=\"wp-block-heading\" class=\"wp-block-heading\">Tay-Sachs Disease<\/h2><h2 class=\"wp-block-heading\" class=\"wp-block-heading\">Hurler Syndrome<\/h2><h2 class=\"wp-block-heading\" class=\"wp-block-heading\">I-cell Disease<\/h2><h2 class=\"wp-block-heading\" class=\"wp-block-heading\">Alpha-1 antitrypsin deficiency<\/h2><\/div>","protected":false},"excerpt":{"rendered":"<p>Phenylketonuria(PKU) Phenylketonuria is a monogenic inborn error of metabolism that is characterized by the presence of phenyl ketones in the urine. It has different causes but the underlying problem is the excess amount of phenylalanine in the blood (Hyperphenylalaninemia). This causes phenylalanine to accumulate in blood and body fluids. Eventually, it is metabolised to phenyl [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1450,"menu_order":2,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1480","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Genetic Diseases: Autosomal Recessive Diseases II &#8211; Meddists<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/genetic-diseases\/genetic-diseases-autosomal-recessive-diseases-ii\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/medical-genetics\\\/genetic-diseases\\\/genetic-diseases-autosomal-recessive-diseases-ii\\\/\",\"url\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/medical-genetics\\\/genetic-diseases\\\/genetic-diseases-autosomal-recessive-diseases-ii\\\/\",\"name\":\"Genetic Diseases: Autosomal Recessive Diseases II &#8211; 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