L6: Dysmorphic Disorders Flashcards
Def of Dysmorphology
Pathogenic Mechanisms of Dysmorphology
Malformation, Deformation, Disruption & Dysplasia
Def of Malformation
- Early arrest or misdirection of normal development of an organ or a part of an organ.
Causes of Malformation
It results from an intrinsic abnormal developmental process.
Types of Malformation
Examples of Malformation
Def of Deformation
- Abnormal form, shape or position of part of body which has differentiated normally.
Causes of Deformation
It results from mechanical forces (extrinsic defect).
Examples of Deformation
- Developmental defect isn’t essentially detectable at birth but develops later and still genetically determined.
…
Def of Disruption
A morphologic defect of an organ or a part of an organ or a larger region of the body.
Causes of Disruption
Results of Disruption
- If it occurs early during gestation → atresia
- If it occurs later in gestation → necrosis
Examples of Disruption
- Cerebral & cerebellar infarction
- Intestinal atresia (not duodenal)
Def of Dysplasia
It is a structural defect.
Causes of Dysplasia
Results of Dysplasia
It affects just one general tissue type throughout the body
Examples of Dysplasia
- Storage diseases (e.g., mucopolysaccharidoses).
- Ectodermal Dysplasia with involvement of skin, hair, nail & teeth.
- Osteogenesis imperfecta: All parts of the skeleton are affected
Difference between:
- Disruption and deformation
- Disruption and malformation
Types of Birth Defects
- Major versus Minor anomalies
- Isolated versus Multiple anomalies
Major versus Minor anomalies
Def of Major Anomalies
Examples of Major Anomalies
- Cleft lip
- Pyloric stenosis
- VSD
- Down syndrome
Percentage of Major Anomalies
3% of newborns
Def of Minor Anomalies
Abnormalities that are of primarily cosmetic significance.
Examples of Minor Anomalies
- Clinodactyly of the 5th finger
- Preauricular tag
- Epicanthal folds
Percentage of Minor Anomalies
14% of newborns
Isolated versus Multiple anomalies
Def of Isolated Anomalies
Anomalies that affect only a single body site.
Incidence of Isolated Anomalies
About 2/3 of major anomalies are isolated
Examples of Isolated Anomalies
- Cleft lip + palate
- Pyloric stenosis
- Congenital heart disease
Def of Multiple Anomalies
- Anomalies that affect multiple sites and have different causes & prognosis
Examples of Multiple Anomalies
- The possible combinations of anomalies are limitless.
- But, as a role, ≥ 2 major anomalies are usually associated with several minor anomalies.
Etiologies of congenital anomalies
Genetic Causes of congenital anomalies
- Chromosomal Abnormalities
- Single Gene Defect
- Multi-Factorial Inheritance
Genetic Causes of congenital anomalies
- Chromosomal Abnormalities
Genetic Causes of congenital anomalies
- Single Gene Defect
Genetic Causes of congenital anomalies
- Multi-Factorial Inheritance
Environmental Causes of congenital anomalies
Unknown Causes of congenital anomalies
- No near cause can be established.
- Risk of recurrence is very low.
Dx Approach for a child with congenital anomalies
- Hx
Dx Approach for a child with congenital anomalies
- Ex
Dx Approach for a child with congenital anomalies
- INVx
Investigations for a child with congenital anomalies
- Chromosomal analysis
Investigations for a child with congenital anomalies
- Rad
Skeletal dysplasia, cardiac & renal anomalies.
Investigations for a child with congenital anomalies
- Autopsy
Should be encouraged if the child has died, in order to:
- define the full extent of anomalies.
- establish the cause of death.
