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 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.