Down Syndrome or Trisomy 21

Down Syndrome or Trisomy 21

Down syndrome or trisomy 21 also called mental retardation is a genetic disorder caused by the presence of an extra 21st chromosome in humans. It is described by a British doctor John Langdon Down in 1866.

Pathophysiology : The extra chromosome 21 affects almost every organ system in the body and then make results in a wide spectrum of phenotypic consequences. Down syndrome decreases prenatal viability, increases prenatal and postnatal morbidity. So far, Affected children have delayed physical growth, maturation, bone development, and dental eruption.

Down+syndrome
Down syndrome Patients have decreased buffering of physiologic reactions, resulting in hypersensitivity to pilocarpine also abnormal responses on sensory-evoked electroencephalographic tracings. Children with leukemic Down syndrome most of them have hyperreactivity to methotrexate.

Physical :

  • Growth: Short stature and obesity occurs during adolescence.


  • Behavior: Natural spontaneity, genuine warmth, cheerful, gentleness, patience, and tolerance are characteristics. A few patients exhibit anxiety and stubbornness.


  • Nose: Hypoplastic nasal bone and flat nasal bridge are typical characteristics.


  • Mouth and teeth: An open mouth with a tendency of tongue protrusion, a fissured and furrowed tongue, mouth breathing with drooling, a chapped lower lip, angular cheilitis, partial anodontia (50%), tooth agenesis, malformed teeth, delayed tooth eruption, microdontia (35-50%) in both the primary and secondary dentition, hypoplastic and hypocalcified teeth, malocclusion, taurodontism (0.54-5.6%), and increased periodontal destruction are noted.


  • Abdomen: Diastasis recti and umbilical hernia occur.

Medical Care :

  • Genetic counseling, If the couple has a child with trisomy 21, the risk of recurrence is about 1%. The risk does not appear to be increased in siblings of affected individuals.


  • Vaccination and medication


  • Medical care and monitoring for the adolescent with Down syndrome.

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