Genetic diseases

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  • Sickle Cell Anemia / Sickle Cell / Falcemia: autosomal recessive (Mendelian), occurs through the change of glutamic acid for valine in hemoglobin. It produces a red blood cell deformed, poor oxygenation in the blood and organs. Common symptoms include paleness, jaundice, fatigue, tachycardia, and stunting in children.
  • Huntington's chorea: codon CAG repeat on chromosome 4 (Anticipation - No Mendelian). It can be passed on to children. Common symptoms: rapid, jerky movements (dance), facial grimacing, antisocial behavior, progressive dementia, unsteady gait and mood.
  • Fragile X Syndrome / Martin & Bell, repetition of CGG codon in the X chromosome gives frail to be viewed by microscope (Anticipation - No Mendelian), most common inherited form of mental retardation. Common symptoms: mental retardation, hyperactivity, attention problems, hyperextensible joints, prominent ears and large testes.
  • Angelman syndrome (happy puppet / happy puppets) defect on chromosome 15 inherited from the mother (impregnated Genomics - No Mendelian). Common symptoms: stiff gait, excessive laughter, epileptic seizures, hyperactivity, lack of language and mental retardation.
  • Prader-Willi syndrome: defect in chromosome 15 inherited from the father (Impregnation Genomics - No Mendelian), patients lack the feeling of satiety. Common symptoms: excessive and constant hunger, deficiency of muscle tone, lack of energy and delay in the development of learning.
  • Marfan syndrome: autosomal dominant (Mendelian) on chromosome 15 that encodes the protein fibrillin. Common symptoms: heart failure, a prominent height, slender limbs and long, spider-like fingers (arachnodactyly), scoliosis (crooked spine) and myopia.
  • Klinefelter syndrome or 47XXY: only occurs in men have one X plus (Aneuploidy). Common symptoms: small penis and testicles, little body hair, enlarged breast tissue (gynecomastia) and infertility.
  • Turner Syndrome / Bonnevie-Ullrich or 45X0: only occurs in women, have less than X (Aneuploidy). Only viable monosomy. Common symptoms: short stature, lack of development of the ovaries and breasts, loss of menstruation, simian crease in hand, webbed neck, and infertility.
  • Down Syndrome / Trisomy 21/Translocación 1914-1921: the existence of an extra chromosome 21 (aneuploidy) or translocation of chromosome 21 to 14. Common symptoms: heart defects, visual or auditory, almond eyes, small ears, small mouth (seems to have a large tongue), flattened nasal bridge and short neck.
  • Phenylketonuria: A rare inherited disease in which the body does not properly metabolize the amino acid phenylalanine can cause mental retardation and severe if treatment is not performed, is a disease that is inherited as an autosomal recessive trait.

The genetically determined abnormality in phenylketonuria is the absence of the enzyme called phenylalanine hydroxylase, as a result, there is an accumulation in the body of high levels of phenylalanine.

The causes brain damagesevere mental retardation at the end of the first year of life. Older children may develop movement disorders ( athetosis ), rocking, and hyperactivity.


Skin rash ( eczema )



Jerking movements of arms and legs ( spasticity )

Unusual positioning of hands



Delayed mental and social skills

Mental Retardation

A distinctive smell of "mouse" in the urine and sweat

Pale (often pale complexion, blond hair and blue eyes.)

Phenylalanine occurs in significant quantities in foods such as milk, eggs and other common foods.

  • Galactosemia: It is the body's inability to use ( metabolize ) the simple sugar galactose (which causes the accumulation of galactose 1-phosphate), which reaches high levels in the body and cause liver damage, central nervous system and various other body systems. It is a hereditary disease transmitted as a trait autosomal recessive .

There are three forms of the disease: deficiency of galactose-1-phosphate transferase (classic galactosemia, the most common and most severe), galactose kinase deficiency and deficiency of galactose-6-phosphate epimerase. People with galactosemia are unable to fully break down the simple sugar galactose, which makes up half of lactose, the sugar found in milk.


  • Jaundice (yellowing of the skin and sclera)
  • Vomiting
  • Poor feeding (baby refusing to drink milk-containing formula)
  • Poor weight gain
  • Irritability
  • Seizures

treatment is carried out in strict abstinence is the consumption of all types of milk and milk products

  • Hurler Scheie syndrome:

Alpha-L-iduronidase; Mucopolysaccharidosis type I, MPS I, Hurler Scheie syndrome, Scheie syndrome (MPS1S)

It is an inherited disease that belongs to a group of diseases called mucopolysaccharidoses, or MPS. Hurler syndrome is inherited as an autosomal recessive trait.

Hurler syndrome (MPS1) is an inherited, progressive disorder that results from the body's inability to produce an enzyme called alpha-L-lysosomal ioduronidasa that helps break down mucopolysaccharides. The enzyme deficiency found in Hurler's syndrome causes the mucopolysaccharides accumulate in the body and the result is a multisystem disorder with symptoms ranging from mild to severe. This disease damages many organs including the heart.

Symptoms: The symptoms of intermediate MPS1 usually develop between 3 and 8 years old and it is common that the person will survive to adulthood.

Hunter syndrome: An inherited disease in which there is a disorder in the breakdown of a mucopolysaccharide (a chemical that is widely distributed in the body outside of cells). This chemical builds up and causes it to present a characteristic facial appearance, abnormal function of multiple organs and, in severe cases, death.

Alternative Names: Mucopolysaccharidosis type II, iduronate sulfatase deficiency

Hunter syndrome is inherited as an X-linked disease

The metabolic abnormality that causes Hunter syndrome is the lack of the enzyme iduronate sulfatase, in whose absence, mucopolysaccharides collect in various body tissues, causing damage. Affected children may develop an early-onset type (severe form) shortly after age 2.


  • Coarse facial features
  • Large head ( macrocephaly )
  • Joint stiffness
  • Increased hair ( hypertrichosis )
  • Deafness (progressive)
  • Enlargement of internal organs like the liver and spleen
  • Abnormal retina (back of the eye)

  • Thalassemia: They are the most common group of disorders in humans in the synthesis of Hb, so inherited. They are a heterogeneous group of disorders and are classified according to the chain or individual globin chains synthesized in small amounts, ie alpha, beta, gamma and delta.

The thalassemias are a heterogeneous group of inherited anemias characterized by decreased or total absence of synthesis of one or more chains of hemoglobin.

It is due to the inheritance of a disease or two alleles of one or more genes on chromosomes 11 and 16 (all received two copies of a gene, one copy from the father and a mother, each of these copies is called an allele).

Thalassemia genes are widely distributed throughout the world, but is mostly found in the Mediterranean coast, much of Africa, the Middle East, Indian subcontinent and Southeast Asia. It is probably the most common genetic disease.

Hemoglobin (Hb) of normal adult consists of a heme (iron carries) and four globin chains. These globin chains are distributed as follows: 97% HbA1 (two chains and two chains b), 2.5% of HbA2 (two chains and two chains d) and HbF (2 g chains and two chains, the predominant in the fetus and in the newborn). Alpha and beta chains are the most important in postnatal life.

Depending on which globin chain is synthesized in smaller amounts (but always were normal globin) is called alpha thalassemia (a) or beta thalassemia (b).

And according to the severity of the disease: thalassemia major (inherit two copies of the gene with a significant alteration in every copy or allele), intermediate (two copies are inherited two moderately impaired or significantly alter and moderate) or minor (also known as thalassemia trait is due to the inheritance of an altered and one normal allele).

Of the various types of these hemolytic anemias, we refer to the most frequent in medical practice:

  • ALFA-thalassemia: Due to insufficient production of alpha-globin chains.

Alpha-thalassemia Alpha-thalassemia

Severa. Leve.

There are no strings are produced

alpha-chain alpha-globin, but

globins. by introducing a very

It is associated with reduced compared

utero death of the beta-globin.

the fetus. It is compatible with life.

- The mapping studies of alpha-globin region on chromosome 16, show that there is structural genes for alpha-globin genes in this chromosome, and the disease is caused by deletions of one or more of these structural genes. These deletions, are thought to have arisen by crossing over in meiosis unpaired.

  • Beta-thalassemia: Due to insufficient production of beta-globin chain

- Rarely is due to a deletion.

- They are responsible for them, a variety of different mutations including: point mutations, insertions and deletions of one or more bases.

- Mutations are classified as:

a) - Mutations of the transcription.

b) - Changes in mRNA unions.

c) - Mutations in the RNA-modifying regions.

d) - Changes in the termination of the chain.

e) - nonsense mutations.

- The affected individuals are usually compound heterozygotes, ie have different mutations in beta-globin genes.

  • Hereditary persistence of fetal hemoglobin: Included in thalassemia and is a persistence of fetal hemoglobin production in childhood and adulthood. These individuals continue to produce significant amounts of fetal Hb after birth.

It is not associated with any symptoms and was originally considered a scientific curiosity rather than a medical problem.

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