Congenital Anomalies (Birth Defects) PDF

CONGENITAL ANOMALIES (Birth defects)  INTRODUCTION A congenital anomaly is a structural abnormality of any type that is present at birth. Congenital anomalies may be induced by genetic or environmental factors. Most common congenital anomalies, however, show the family...

CONGENITAL ANOMALIES (Birth defects)  INTRODUCTION A congenital anomaly is a structural abnormality of any type that is present at birth. Congenital anomalies may be induced by genetic or environmental factors. Most common congenital anomalies, however, show the family patterns expected of multifactorial inheritance (determined by a combination of genetic and environmental factors). About 3% of all liveborn infants have an obvious major anomaly. The incidence is about 6% in 2-year-olds and 8% in 5-year-olds. Congenital anomalies may be single or multiple and of minor or major clinical significance.  Causes of congenital anomalies 1-Genetic factors such as chromosomal abnormalities and mutant genes. 2-Environmental factors e.g.: the mother had German measles in early pregnancy will cause abnormality in the embryo. 3-Combined genetic and environmental factors (mutlifactorials factors).  Types of abnormalities 1-Malformations: this occurs during the formation of the structures of the organ (during organogenesis) results in partial or complete non formation or alterations in the normal structure. This occurs in the 3rd to the 8th week of gestation. Ex. Cleft lip and or cleft palate. 2-Disruptions: results in morphological change of the already formed structure due to exposure to destructive process. e.g.: vascular accidents leading to intestinal atresia, amniotic band disruption. 3-Deformations: due to mechanical forces that affect a part of the fetus over a long period. Ex: talipes equinovarus deformity. 4-Syndrome: is a group of anomalies occurring together due to a common cause. Ex: Down Syndrome: Trisomy 21. Mental retardation, characteristic facial features, Simeon crease in hand.  Trisomy Trisomy is a condition similar to triploidy. It occurs when only certain pairs of chromosomes (the 13th, 18th, and 21st chromosomes being the most common) get an extra chromosome in every cell. The most common types of trisomy are: trisomy 13, or Patau syndrome trisomy 18, or Edwards syndrome trisomy 21, or Down syndrome  Common Problems cont. Muscular and skin problems: Polydactyly, or extra fingers/toes Low-down ears Prominent heels and deformed feet, called ‘rocker-bottom’ feet Strange palm patterns, commonly called the Simian line Overlapping of the fingers over thumb Cleft palate Polydactyly The Simian line ‘Rocker-bottom’ feet 7  Common Problems, cont. Vascular Problems: Kidney problems Heart defects such as ventricular septal defect The disease shown right is called Polycystic kidney disease (PKD). This is a disorder in which clumps of cysts develop within your kidneys. Cysts are Kidney Problem small round sacs containing water-like fluid. Cayden Phipps: 3A - 8 Abrams  Trisomy 18- Edwards syndrome Trisomy 18 (also known as Edward syndrome) is a chromosomal condition in which all or a part of chromosome 18 is present in the cells of the body three times (trisomy) rather than the usual two times Mental deficiency; growth retardation; prominent occiput; short sternum; ventricular septal defect; micrognathia; low-set malformed ears, flexed digits, hypoplastic nails; rocker-bottom feet.  Turner syndrome ((45,X or a female missing one X), and Klinefelter syndrome (47,XXY or a male person with an extra X chromosome). Klinefelter syndrome- XXY trisomy Small testes, hyalinization of seminiferous tubules; aspermatogenesis; Often tall with disproportionately long lower limbs. Intelligence is less than in normal siblings. Approximately 40% of these males have gynecomastia  Structural chromosomal anomalies include chromosomal deletion, duplication, translocation, inversion, and ring and iso chromosomes. It may also lead to severe congenital anomalies or fetal death. Teratogens  Terminology Definition: any environmental agent that causes damage to the fetus during prenatal period. – viruses, drugs, chemicals, and radiation – others categories? 95% of all newborns are normal. Of the remaining 5%, – 3% have mild, temporary or reversible defects. – only 2% having continuing effects. Effect- What happens- the developmental outcome or consequence of exposure to a teratogen- variation in the development of the embryo, fetus, or child. Mechanism- How it happens- the physiological or biological processes that explain the cause or how specific events occur  Environmental factors 1) Infectious Agents: 1-Infectious agents include a number of viruses: n Rubella used to be a major problem. It causes cataract, glaucoma, heart defects and deafness. n Cytomegalovirus :The infection is often fatal and if not meningoencephalitis produce mental retardation. n Herpes simplex, varicella and human immunodeficiency viruses are other examples. 2- Toxoplasmosis 3- Syphilis : leads to congenital deafness and mental retardation.  Environmental factors 2)Radiation : Ionizing radiation kills rapidly proliferating cells, producing any type of birth defect depending upon dose and stage of development. Ex. Atomic bomb on Hiroshima and Nagasaki. Exposure of the pregnant woman to a large dose of x- ray can lead to microcephaly, spina bifida or cleft palate.  Environmental factors 3) Chemical agents: There are many dangerous drugs, if have given to the pregnant female, can produce congenital anomalies. Ex.: - Thalidomide (antinauseant sleeping pills) produce limb defects (phocomelia) and heart malformations. - Diphenylhydantoin produce facial defects and mental retardation. Tetracycline (bone and teeth anomalies) Aspirin may cause harm in large doses. Cocaine cause birth defect possibly to its effect as a vasoconstrictor that cause hypoxia. Alcohol cause fetal alcohol syndrome.  Environmental factors 5)Hormones: n Androgenic agents (synthetic progestin to prevent abortion) cause masculinization of the genitalia of female embryos. n Endocrine hormones as Diethylstilbestrol cause malformation of the uterus, uterine tubes, upper vagina, vaginal cancer and malformed testes. n Insulin which treat diabetes of the mother à congenital anomalies. n Cortisone (in large doses) may cause cleft palate.  Environmental factors 6)Maternal Disease: Diabetes cause variety of malformations as heart and neural tube defects. 7)Nutritional deficiency: particularly vitamins deficiency. 8)Heavy metals: Eg: organic mercury.  PRENATAL DIAGNOSIS Methods of prenatal diagnosis are divided into invasive and non-invasive techniques. Technique Time Disorders diagnosed (in weeks) A. Non-invasive: Maternal serum screen: Alpha feto protein (AFP) 16 Neural tube defects (NTD) Triple test 16 Down syndrome Ultrasound 18 Structural defects in many organs as CNS, heart, kidney, and limbs. B. Invasive: - Amniocentesis 14-16 Chromosomal and metabolic abnormalities, and DNA analysis. - Chorionic villus sampling 10-12 As amniocentesis. - Fetal blood sample near term As amniocentesis + blood disorders. Technique of amniocentesis Technique of CVS U/S showing polydactyly U/S showing micrognathia U/S showing Umibilical hernia (associated with Trisomy 18 in 50% of cases)  Trisomy 21, or Down syndrome Trisomy 21 (47, +21), - 94 %, The frequency of trisomy increases with increasing maternal age  Clinical Features Head and neck Extremities Brachycephaly Short broad hands Up-slanting palpebral fissures Short fifth finger Epicanthal folds Incurved fifth finger Brushfield spots Flat nasal bridge Transverse palmer crease Folded or dysplastic ears Space between first and second Open mouth toe Protruding tongue Hyper flexibility of joints Short neck Excessive skin at the nape of neck  Neonatal features Flat facial profile Dysplasia of pelvis Poor Moro reflex Anomalous ears Excessive skin at the Dysplasia of nape of neck midphalanx of fifth Slanted palpebral finger fissures Transverse palmer Hypotonia crease Hyper flexibility of joints