The formation of secondary palate starts with the growing of tissues vertically and mesially forming the right and left lateral palatal shelves. On the week 8, the tongue will be withdrawn downwards and the right and left lateral palatal shelves will be rapidly elevated, flipped into a horizontal orientation and fuse together from the front to the back two. The right and left lateral palatal shelves contact or fuse with each other at the midline to form the secondary palate two.A lot of growth factors are actively involved in the signalling to the tissues during craniofacial development. These growth factors function to control the cells proliferation, survival and apoptosis. Some of the growth factors that can be implicated in the facial development resulting in craniofacial defect are BMP, FGF, Shh, Wnt and endothelins. One of the environmental factors that has been identified in mice study to have link to cleft lip is teratogen which can interfere the molecular signalling between the growth factors. However, the exact mechanism is still not clear. Another environmental factors that has been actively involved in studies to prevent cleft lip and palate occurrences is the intake of folic acid during pregnancy. 0.4 mg folic acid intake per day has been shown to reduce one third risk of cleft lip (with or without cleft palate) in babies. However, it seems had no apparent effect on the risk of cleft palate alone.
Meacham syndrome is a rare genetic disorder which is characterized by lung, diaphragmatic and genitourinary anomalies. Signs and symptoms
Often people with this condition are born with both underdeveloped lungs and a herniated diaphragm. Urinary symptoms include a horseshoe kidney
Genital symptoms are different according to the biological sex of the baby, genetic males (46,XX) usually have pseudohermaphroditism, ambiguous genitalia, and perineal hypospadias. Genetic females (46,XX) often have septate uterus and duplication of the vagina. In some cases, karyotype is needed to know the biological sex of the baby.Additional symptoms include neoplasm, cryptorchidism, ventricular septal defect, atrial septal defect, hernia, patent ductus arteriosus, Tetralogy of Fallot, and penile hypoplasia. Causes
This condition is caused by an autosomal dominant missense mutation in the WT1 gene, in chromosome 11. This was found through two half-siblings reported by Suri et al. Epidemiology
According to OMIM, only 12 cases have been described in medical literature. == References ==