Updated: 11/18/2019

Inheritance Patterns of Orthopaedic Syndromes

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Introduction
  • Allows for specific patterns of inheritance controlled by a single gene pair (“monogenic”)  
    •  4 different types of patterns
      • autosomal dominant
      • autosomal recessive
      • x-linked dominant
      • x-linked recessive
    • additional inheritance effects include
      • imprinting
      • anticipation
  • In general
    • defective structural proteins = AD
    • defective enzymes = AR
Pedigree Analysis
  • A pedigree chart displays a family tree and the members of the family affected by a genetic trait
  • Use
    • a pedigree chart can be used to determine the mode of transmission
    • dominance
      • whether the trait is dominant or recessive
    • linkage
      • whether the trait is X-linked or autosomal
  • Key
    • shapes
      • circles represent females
      • squares represent males
    • color
      • a black circle/square represents an individual affected by the genetic trait
      • a white circle/square represents an individual that is not affected by the trait 
    • lines
      • horizontal
        • a male and female connected by a horizontal line have mated and have children
      • vertical
        • vertical lines connect parents to their children
Autosomal Dominant
  
  • Description
    • only need to get the abnormal gene from one parent in order for you to inherit the disease.
  • Examples 
    • Syndactyly 
    • Polydactyly 
    • Marfan's syndrome 
    • Cleidocranial Dysostosis 
    • Hereditary Multiple Exostosis 
    • Achondroplasia 
    • MED 
    • Metaphyseal chondrodysplasia (Schmid and Jansen types) 
    • Kniest dysplasia 
    • Malignant hyperthermia 
    • Ehlers-Danlos syndrome 
    • Osteogenesis imperfecta (types I and IV) 
    • Osteochondromatosis/Multiple Hereditary Exostosis 
    • Osteopetrosis (tarda, mild form) 
Autosomal Recessive
  
  • Description
    • an autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.
  • Examples  
    • Diastrophic Dysplasia 
    • Friedreich's Ataxia 
    • Gaucher disease  
    • Spinal muscular atrophy 
    • Sickle cell anemia 
    • Osteogenesis imperfecta (II and III) 
    • Hypophosphatasia 
    • Osteopetrosis (infantile, malignant form) 
Sex-linked Recessive (males only)
  
 
  • Description
    • X-linked diseases usually occur in males. Males have only one X chromosome. A single recessive gene on that X chromosome will cause the disease.
  • Examples
    • Duchenne muscular dystrophy 
    • Becker's muscular dystrophy 
    • Hunter's syndrome 
    • Hemophilia  
    • SED tarda 
Sex-linked Dominant
 
  • Examples
    • Hypophosphatemic rickets 
    • Leri-Weill dyschondrosteosis (bilateral Madelung's deformity) 
Multiple inheritance patterns
  • Examples
    • Charcot-Marie-Tooth (AD, AR, Xlink) 
    • Osteopetrosis (AD, AR) 
    • Osteogenesis Imperfecta (AR, AD) 
    • Neurofibromatosis (AD, AR) 
    • SED (AD, Xlink) 
Miscellaneous Genetic Inheritance
  • Imprinting
    • a genetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner 
    • Examples
      • Angelman Syndrome
      • Prader-Willi Syndrome 
  • Anticipation
    • a phenotype occurs earlier (and typically worse) in each subsequent generation   
    • common in trinucleotide repeat disorders

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