Down syndrome (DS), also called Down’s syndrome, Trisomy 21, trisomy G, or Mongolism, is one of the most common chromosomal (genetic) disorders presenting with intellectual disability and is associated with many other systemic complications. This syndrome is characterized by an additional copy of chromosome 21, either full or partial. The chromosomal aberration occurs during the meiotic phase of cellular division. In the USA, as of 2013, approximately 1 baby in every 700, had DS. Increased maternal age significantly increases the risk of DS in the offspring. In 2013, around 3,400 DS–related elective pregnancy terminations were reported in the USA, resulting in a 33% reduction in the number of babies with DS that would have been born in that year. In the USA, an increased prevalence of DS live births began in the 1980s which leveled off after 2005.
DS is a multisystem disorder that affects the individual physically, medically, and psychologically. Following are some of the obvious symptoms of DS:
Flat facial profile
Excessive skin at the nape of the neck (nuchal folds)
Slanted palpebral fissures
Poor motor reflex
Dysplasia of mid phalanx of the 5th finger
Single transverse palmar crease
Hyper flexibility of joints
Other findings include – characteristic brush field spots in the iris of the eye, cardiac murmur, poor respiratory effort, poor suck reflex, abdominal distension, and vomiting.
A physical examination carried out within the first 24 hours of birth is crucial in diagnosing DS. Prenatal screening for DS helps identify high-risk pregnancies and avoid a miscarriage, hence, is part of the routine investigations in a confirmed pregnancy, in most countries across the globe. No screening procedure can accurately detect DSs in all cases, false positive/negative results must be suspected. Nevertheless, many screening and diagnostic modalities are practiced for DS and the routinely used screening methods are ultrasound scan and maternal serum biochemical analysis, especially in the 1st and 2nd trimesters of pregnancy. The ultrasound characteristics of DS include increased nuchal translucency and an absent nasal bone. Maternal serum biochemical analytes, identified as indicators of a DS conceptus which include α–fetoprotein, β–human chorionic gonadotropin (HCG), unconjugated estriol, and inhibin A, and pregnancy-associated plasma protein (PAPP-A). The HCG and PAPP-A levels are measured via a blood test at 9-12 weeks of pregnancy. The invasive tests - amniocentesis and chorionic villi sampling (CVS) are offered when prenatal screening has established a high risk of DS conceptus.
Every individual with DS presents themselves with a unique set of strengths and challenges that emerge throughout their lifespan. Periodic screening is recommended for the various systemic comorbidities present in DS and the management of DS is largely dictated by the existing comorbidities and their severity. Prenatal management involves regular monitoring and counseling of pregnant women carrying a fetus with a confirmed diagnosis of DS. The American Academy of Pediatrics (AAP) has provided a guideline on age-wise supervision of the overall health of individuals with DS. ACEI drugs may benefit in cardiac issues, anticonvulsants may reduce the frequency of seizures, standard immunization protocol is followed to prevent infections, physical/exercise therapy helps improve muscular strength, periodic screening is recommended for gastrointestinal disorders, hearing aids are useful and vision defects errors can be corrected by aids/devices and/or surgery, especially for correction of cataract or glaucoma or keratoconus, and psychotherapy and counseling help in improving cognitive functioning. Early therapeutic intervention is necessary to improve the quality of life. Most individuals with DS can live almost independently, with adequate support and therapy.