Pediatric
Chromosomal anomalies
Trisomy 21

Author: Elena Puscasiu, M.D. (see Authors page)

Revised: 19 April 2016, last major update February 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Trisomy 21 [title] pediatric

Related: Congenital anomalies general, Trisomy 18, Trisomy 13


Cite this page: Trisomy 21. PathologyOutlines.com website. http://pathologyoutlines.com/topic/pediatrictrisomy21.html. Accessed January 23rd, 2017.
Terminology
  • Trisomy 21 syndrome, Down syndrome
Essential Features
  • General:
    • Hypotonia with open mouth and protrusion of the tongue
    • Hyperflexibility of joints
    • Small stature
  • CNS: intellectual disability
  • Craniofacial:
    • Brachycephaly
    • Up slanting palpebral fissure
    • Small nose with low nasal bridge
    • Inner epicanthic folds
    • Flat facial profile
  • Eyes:
    • Myopia
    • Nystagmus
    • Strabismus
    • Cataracts
  • Ears:
    • Small
    • Hearing loss
  • Dentition:
    • Hypoplasia
    • Irregular placement
  • Neck: short with loose folds of skin
  • Hands:
    • Short metacarpals and phalanges
    • Hypoplasia of midphalanx of fifth finger
    • Single crease
    • Simian crease
  • Feet: wide gap between first and second toe
  • Pelvis: hypoplasia
  • Cardiac:
    • Anomaly in approximately 40%
    • Endocardial cushion defect
    • Ventricular septal defect
    • Patent ductus arteriosus
    • Atrial septal defect
  • Skin:
    • Cutis marmorata
    • Dry, hyperkeratotic skin with time
  • Hair: fine, soft, sparse
  • Genitalia:
    • Small penis and testicles
    • Cases of fertility in female reported
    • No male has reproduced
Epidemiology
  • The most common pattern of human malformation: 1 in 660 newborns
  • The risk increases with increasing maternal age (1:1000 at age 20; 1:300 at age 35; 1:95 at age 40)
Pathophysiology
  • 95% are due to nondisjunction and 4% are due to translocation (most frequent between chromosomes 21 and 14)
Prognostic Factors
  • 50% of fetuses die prenatally
  • 40% of liveborn children die within first year of life
  • Many (15%) who live 40 years or longer develop Alzheimer disease
    • Of those who reach 60 years of age, 50 - 70% have the disease
  • Although the overall risk of cancer is not changed, the risk of leukemia and testicular cancer is increased, but the risk of solid cancers is reduced
  • Leukemia is 10 - 15 times more common in children with Down syndrome
    • Acute lymphoblastic leukemia is 20 times more common, and the megakaryoblastic form of acute myelogenous leukemia is 500 times more common
    • Transient myeloproliferative disease, a disorder of blood cell production that does not occur outside of Down syndrome, affects 3 - 10% of infants
      • This disorder is typically not serious but occasionally can be
      • It usually resolves without treatment, but carries a 20 - 30% risk of developing acute leukemia
  • Solid cancers are believed to be less common due to increased expression of tumor suppressor genes present on chromosome 21
Clinical Images

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Features

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Facial features

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Brushfield spots

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Epicanthal folds

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Transverse crease

Micro Images

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Cystic Hassall's corpuscles

Molecular / Cytogenetics Description

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Typical karyotype