Down’s syndrome

Down syndrome is the most common chromosomal disorder reported in humans and the most common cause of Intellectual disability. Reported incidence is approximately 1 in 700 live newborns. 

Clinical diagnosis

Children with Down syndrome have characteristic dysmorphic features such as uplslant of eyes, brachycephaly, midface hypoplasia, small nose, flat nasal bridge, small ears, open mouth and protruding tongue, simian crease and sandle gap in the feet. 

Despite the facial gestalt, clinical diagnosis can be difficult in newborns and certain ethnicities. Halls criteria can be useful to clinically diagnose a newborn or child with Down syndrome. 

Halls criteria, first published in 1966, consist of 10 signs typically seen in this syndrome: 

  1. Hypotonia
  2. Poor moro’s reflex, 
  3. Flat face 
  4. Upward slant of palpebral fissures
  5. Small dysplastic ears
  6. Joint hyper flexibility
  7. Short neck and redundant skin
  8. Short 5th digit with clinodactyly
  9. Single transverse palmar crease
  10. Pelvic dysplasia. 

Associated morbidities in Down’s 

  • Congenital heart defects (50%) particularly septal defects (AVSD, VSD, ASD)/PDA/TOF
  • Developmental delay and short stature – universal in all the children. 
  • Hypothyroidism is common and warrants evaluation and treatment. 
  • Other reported abnormalities include, thrombocytopenia, leukaemia’s, gastrointestinal anomalies and Atlanto-axial instability. 
  • Later childhood, refractive errors, periodontal disease, conductive hearing loss, celiac disease.
  • Alzheimer disease in adulthood are reported with an increased incidence.

Lab Diagnosis

Karyotype (3ml blood in Heparinised vial) is essential in all suspected children to confirm the diagnosis and type of Down syndrome, 

Look for mosaicism (may be milder), evaluate recurrence risk and offer genetic counselling. If the karyotype is normal, consider Down like syndromes! 

In very sick babies, FISH test may be done for rapid diagnosis. 

Although there is no cure for Down syndrome, early intervention programs and monitoring shows significant benefit and improves quality of life for these children and their families. 

Post Pic : Smith’s Recognisable patterns of Human malformations, Seventh Ed, Elsevier, Philadelphia

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