6 Etiology of Diseases

Cards (145)

  • Genetic disorder is a pathological condition caused by an absent/defective gene or by a chromosomal aberration.
    • Humans have 30,000 genes that can involve in changes to their structure, causing diseases.
  • Hereditary disorders are diseases derived from parents.
    • caused by genetic mutations or variations passed down from one parent to their children.
    • genetic mutations may affect a single or multiple genes
  • Familial disorders are diseases transmitted in gametes through generations.
    • refers to diseases that runs in families but may not necessarily be caused by genetic mutations.
    • can result from environmental or lifestyle factors among the family members.
  • Congenital disorders are diseases present at birth.
  • Genetic disorder → there is a mutation
    • It implies that there are permanent changes in DNA.
  • Mutations affects:
    • Germ cells – transmitted to progeny
    • Somatic cells – not transmitted but causes cancers or malformations.
  • Point mutations or missense mutations are substitution of a single nucleotide base resulting in replacement of single amino acid in protein molecule
  • An example of point mutation is Sickle-cell anemia, where there is a mutation resulting in substitution of valine for glutamic acid at position 6 of ß-globin protein
  • Frameshift mutation is the insertion/deletion of one or two base pairs; changes DNA reading frame.
  • An example of Frameshift mutation is Tay-sach's disease, which is caused by a frameshift mutation in the hexagene
  • Trinucleotide repeat mutations are mutations where there are amplification of 3 sequential nucleotides.
  • Mendelian disorder results from mutation in single genes; diseases are hereditary and familial.
    includes many uncommon conditions such as:
    • storage diseases
    • inborn errors of metabolism
  • Complex disorders involves multiple genes as well as environmental influences or sometime called multifactorial diseases.
    includes some of the most common disorders of mankind:
    • hypertension
    • diabetes
    • allergic & autoimmune diseases
  • Chromosomal abnormalities are changes in the number or structure of chromosomes.
    • several rare developmental abnormalities are attributable to chromosomes alterations.
  • Mendelian disorder are diseases caused by single-gene defects and it follows mendelian pattern of inheritance
  • Autosomal Dominant disorders manifests heterozygous states (not AA/BB→ occurs at AB); there is a mutation of one allele.
    • at least one parent is affected, males/females; both can transmit.
    • enzyme proteins not affected but receptors and structural protein are involved; onset late sometimes.
  • In autosomal dominant disorder, if an affected person marries an unaffected individual, every child has a 50% chance of inheriting the disorder
  • Marfan syndrome is inherited and affects connective tissue; it most commonly affects heart, eyes, blood vessels, and skeleton.
  • Achondroplasia syndrome is a disorder of bone growth that prevent the changing of cartilage; particularly in bone of arms and legs.
    • characterized by dwarfism
    • limited range of motion at elbows
  • Nervous system autosomal dominant disorders:
    • Huntington’s disease
    • Neurofibromatosis
    • Myotonic dystrophy
    • Tuberous sclerosis
  • Urinary system autosomal dominant disorder:
    • Polycystic kidney disease
  • Gastrointestinal system autosomal dominant disorder:
    • Familial polyposis coli
  • Hematopoietic system autosomal dominant disorders:
    • Hereditary spherocytosis
    • Von Willebrand disease
  • Skeletal system autosomal dominant disorders:
    • Marfan syndrome
    • Ehlers-Danlos syndrome
    • Osteogenesis imperfecta
    • Achondroplasia
  • Metabolic system autosomal dominant disorders:
    • Familial hypercholesterolemia
    • Acute intermittent porphyria
  • Autosomal Recessive disorders are the largest group; both copies (allele) are mutated
    • parents asymptomatic (trait), children shows disease
    • siblings → 1 in 4 chance of being affected (25% risk)
    • possibility more in consanguineous marriage
    • males and females equally affected; early onset
    • involves enzyme proteins
  • Metabolic system autosomal recessive disorders:
    • Cystic fibrosis
    • PKU
    • Galactosemia
    • Homocystinuria
    • Lysosomal storage diseases
    • A1 – Antitrypsin deficiency
    • Wilson disease
    • Hemochromatosis
    • Glycogen storage diseases
  • Hematopoietic system autosomal recessive disorders:
    • Sickle cell anemia
    • Thalassemia
  • Endocrine system autosomal recessive disorder:
    • Congenital adrenal hyperplasia
  • Skeletal system autosomal recessive disorders:
    • Ehlers-Danlos syndrome (some variants)
    • Alkaptonuria
  • Nervous system autosomal recessive disorders:
    • Neurogenic muscular atrophies
    • Friedrich ataxia
    • Spinal muscular atrophy
  • X-linked disorders are sex-linked disorders
    • most are recessive.
    • transmitted by heterozygous females to their sons.
    • affected males do not transmit to sons, but daughters become carriers.
  • Duchenne muscular dystrophy is one of the severe forms of inherited muscular dystrophy; most common hereditary neuromuscular disease that does not exhibit predilection in any race or ethnicity.
  • Mutation in dystrophin gene leads to muscle fiber degeneration weakness
  • Musculoskeletal system X-linked disorder:
    • Duchenne muscular atrophy
  • Blood system X-linked disorders:
    • Hemophilia A & B
    • Chronic granulomatous disease
    • G6PD deficiency
  • Immune system X-linked disorders:
    • Agammaglobulinemia
    • Wiskott-Aldrich syndrome
  • Metabolic system X-linked disorders:
    • Diabetes insipidus
    • Lesch-Nyhan syndrome
  • Nervous system X-liked disorder:
    • Fragile X syndrome
  • Chromosomal abnormalities are genetic disorders caused by changes in the number structure of chromosomes.
    • these changes can occur spontaneously during cell division or can be inherited from one or both parents.