Genetic Etiology Of Cleft Lip And Cleft Palate
Write short note on etiology of cleft lip and palate.
Answer.
Etiology of cleft lip and palate
Syndromic Cleft Cases
“Speech issues caused by genetic cleft palate”
In syndromic cases, clef occurs by monogenic mode of transmission, i.e. by a single mutant gene producing a large effect. Over 300 syndromes have been reported in the literature which have associated cleft along with other defects.
Velocardiofacial syndrome (velum = palate, cardia = heart, facies = face) is the most common syndrome to exhibit cleft.
genetic causes of cleft lip
“Understanding the genetic causes of cleft lip and palate”
The features include the following:
- Clef palate
- Cardiac defects
- Characteristic facial appearance
- Learning problems and speech
- Feeding problems.
“Pathophysiology of genetic cleft lip and palate explained”
Non-syndromic Clefts
Recent investigations show that both heredity and environmental factors act together in causation of non-syndromic cleft. Such a mode of transmission of a defect/trait caused by interaction of multiple genes and multiple environmental factors is known as multifactorial inheritance.
“Importance of genetic testing for cleft lip and palate”
Hereditary
In contrast to syndromic cleft caused by single mutant gene, cleft in non-syndromic patients are caused by multiple genes (polygenic), each producing small effects which together create this condition. Every individual carries some genetic liability for clefting, but there is no clef formation until the threshold level for expression is reached. When the total genetic liability of an individual reaches a certain level, the threshold for expression is reached and clef occurs.
“Chromosomal abnormalities causing cleft lip and palate”
Environmental Factors
- Recent studies have shown that environmental factors play a significant contributory role at the critical time of embryo- genic development when lip and palatal shelves are fusing.
- A number of environmental factors have been suggested as causative factors including:
- A defective vascular supply to the area involved during critical time of embryonic development.
- A mechanical disturbance in which size of the tongue may prevent union of parts.
- Excessive concentration of circulating substances such as alcohol, certain drugs i.e. teratogens (antibiotics, steroids, insulin) and toxins.
- Viral infections.
- Exposure to radiation.
- Hypoxia.
- Vitamin deficiencies.
- Stress.
“Role of IRF6 gene mutations in cleft palate”
“Impact of TBX22 gene defects on cleft palate”
Multifactorial Etiology
As per the recent studies, the etiology of clef lip and palate cannot be attributed solely to either the environmental or the genetic factors. It also involves more than one factor.
“Facial deformities linked to genetic cleft conditions”
cleft lip genetic disorder
Risk of Producing a Child with Cleft Deformity
- Every parent has approximately 1 in 700 risk of having a child with a cleft
- Parents having a child with a clef have increased risk of having the 2nd child affected 2-5%.
- If more than one person in immediate family has a cleft risk rises to 10-12%.
- A parent having a cleft has 2-5% chance of having a child with a cleft
- If a syndrome is involved, the risk for recurrence within a family can be as high as 50%.
- Maternal age-increased risk of clefting is observed when age of conceiving is late.
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