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Unformatted text preview: Congenital and Genetic Diseases Congenital= present at birth (can be genetic but doesn’t have to be) Genetic= determined by genes (inherited; at birth OR in adulthood) I) Congenital Abnormalities (morphological defects present at birth; may or may not be a genetic basis for those defects; most common cause of mortality in 1 st year of life) • 1. Malformations= result from intrinsically abnormal developmental process; usually multifactorial rather than the result of a single gene or chromosomal defect; ex polydactyly (extra digit), spina bifida, congenital heart disease • 2. Deformations= results from mechanical forces (extrinisic) ; nothing intrinsically wrong with limb/organ (small uterus, large fetus, leiomyomas, oligohydraminios—decreased amniotic fluid so decreased cushioning; compression of fetus by biochemical force is the most common); localized or generalized compression of the growing fetus by abnormal biochemical forces; ex positional abnormalities of the feet (clubbed foot); extrinsic cause of abnormality that can be localized or generalized • 3. Disruptions= result from break down of a normal developmental process ( sudden development—acute event); extrinsic disturbance in morphogenesis are not inheritable and are not associated with risk of recurrence in subsequent pregnancies; from secondary destruction of an organ or body region that was previously normal in development; usually extrinsic in etiology; ex limb amputation due to an amniotic band (cuts off circulation and constricts growing limbs) • Sequence= multiple congenital anomalies result from secondary effects of a single localized aberration in organogenesis; initiating event may be a malformation, deformation or disruption • Agenesis= complete absence of organ • Aplasia/ hypoplasia= incomplete or underdevelopement of an organ • Atresia= absence of an opening • 4. Syndrome= a characteristic association of several anomalies; usually a combo of malformation and deformation; caused by a single etiologic agent affecting several tissues; may or may not be sequential; ex potter syndrome= both malformations and deformations; basic defect is absent or abnormal kidney development (malformation —intrinsic) resulting in decreased amniotic fluid (deformation-oligohydramnios) and compression of the fetus; these lead to abnormal development of the lung (deformation—pulmonary hypoplasia) and death due to respiratory insufficiency; fetal compression also produces abnormal facies and abnormal positioning of hands and feet; low set ears; usually don’t survive • Virtually all chromosomal syndromes are associated with congenital malformations Teratogens • Agents that produce congenital malformations • 50% of causes of congenital abnormalities are UNKNOWN; 12-25%=genetic; 8- 13%= environmental (teratogen—mother exposed to specific agents); 20-25%= multifactoral • **teratogens usually cause malformations (technically represent disruptions) • 1. Congenital Infections (mother infected while pregnant)...
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- Spring '11
- Pathology, Congenital heart disease, Mental retardation, Genetic disorder