Indistinguishable From Trisomy 18 Distal 1 3 example essay topic

TRISOMY 18 SYNDROME DEFINITION: A chromosomal disorder resulting in a syndrome characterized by specific (small) dysmorphic features and organ malformations. EPIDEMIOLOGY: incidence: 1/8000 live births most die in embryonic or fetal life 2nd most common autosomal aberration 2nd most common multiple malformation syndrome age of onset: newborn risk factors: advanced maternal age F M (4: 1) HISTORY: 1960 first recognized as a specific clinical entity by the discovery of an extra chromosome 18 in babies with a particular pattern of malformation by three independent groups (Edwards et al., Palau et al., Smith et al.) PATHOGENESIS: 1. Genetics 1. Trisomy 18 90% of cases due to meiotic nondisjunction less than 1% recurrence rate 2. Mosaicist 10% of cases due to post zygotic (post fertilization) mitotic nondisjunction leads to the partial clinical expression of Trisomy 18 with a longer survival 3. Translocations very rare give rise to partial trisomy 18 syndromes short arm: causes non-specific clinical features with mild or no mental deficiency long arm: entire: clinically indistinguishable from trisomy 18 distal 1/3 - : partial clinical picture of trisomy 18 with a longer survival and less profound mental retardation CLINICAL FEATURES: 1.

Dysmorphic Features 1. Facial microcephaly with prominent occiput narrow bi frontal diameter short palpebral fissures low-set malformed ears cleft lip +/- palate narrow palatal arch micrognathia 2. Skeletal neck webbed chest short sternum widely spaced nipples hips: small pelvis, congenital dislocation of the hips, limited hip abduction extremities: phocomelia rocker bottom feet or equino varus short dorsiflexed big toes fixed flexion deformity of the fingers (overlapping of the 2nd and 5th fingers over the 3rd and 4th fingers) simple arch pattern of the fingers and toes hypoplasia of fingernails single crease of 5th finger or all fingers (absence of interphalangeal flexion creases) simian crease 2. Organ Malformations 1. Central Nervous System severe mental retardation hypotonic - hypertonic neural tube defects poor suck and weak cry failure to thrive ocular anomalies 2. Respiratory apnea 3.

Cardiovascular ( 95%) major: VSD, ASD, PDA minor: transposition, ToF, coarctation, anomalous coronary artery, dextrocardia, aberrant subclavian artery, arteriosclerosis, PS, bicuspid aortic and / or pulmonic valves 4. Gastrointestinal inguinal, umbilical, and / or diaphragmatic hernia congenital defects: diastasis recti, hetero topic pancreas, mal rotation, Meckel's, tracheoesophageal fistula 5. Genitourinary cryptorchidism congenital defects: double ureter, ectopic kidney, horseshoe kidney, hydro nephrosis, polycystic kidney INVESTIGATIONS: 1. Imaging Studies to rule out organ malformations: cardiovascular anomalies - Echo gastrointestinal anomalies - Barium Swallow, Endoscope genitourinary anomalies - Ultrasound 2. Karyotyping MANAGEMENT: 1. Supportive very poor prognosis with: 30% dying by 1 month of age 50% dying by 2 months of age 90% dying by 12 months of age genetic counselling recurrence rate depends on genotype.