Meckel syndrome is a genetic disorder affecting multiple organs of the body. This condition is characterized by the sac-like protrusion of the brain at the back of the skull (encephalocele), enlarged kidneys with fluid-filled cysts and the presence of extra digits (polydactyly). Commonly, death occurs with most of the affected infants shortly after the birth as the result of respiratory problems or kidney failure.
Causes
This syndrome develops as the result of the mutations in one of at least eight identified genes. The proteins produced by these genes play an important role in the cell structures called cilia which are the finger-like projections that are essential for the signaling pathways for the transmission of information between the cells. The cilia are important for various functions in the brain cells, the kidneys and the liver. The genetic mutation results in the problem with the normal function and the structure of the cilia which affects the chemical signaling pathways in the early development of the fetus. Meckel syndrome is inherited in an autosomal recessive pattern meaning both the copies of the genes in each cell are defective. The parents of the affected individuals are each the carrier of a single copy of the defective gene and don’t necessarily show symptoms associated with this condition.
Symptoms
The symptoms of this condition vary greatly among the affected cases. The abnormality of the kidney, the lungs and the central nervous system causes the death of the affected infant. The common symptoms are the occipital encephalocele; a condition that presents a gap in the skull and the membranes that cover the brain often protrude. The occipital encephalocele causes the accumulation of cerebrospinal fluid in the skull resulting in the build-up of pressure on the brain tissues (hydrocephaly). The distinctive facial features include abnormally small jaw, low-set malformed ears, cleft palate, short neck and cleft lip. The multiple cysts of the kidney tissues are also common among these affected cases resulting in improper kidney function and renal failure. They infants also have the extra fingers and toes and the webbing of the digits. The abnormalities of the genitourinary tract include the failure of the testes to descend into the scrotum (cryptorchidism), a problem with the normal development of genitalia and the underdeveloped bladder. In some cases, they can also present abnormalities of the additional organs such as the liver, lungs and the heart.
Diagnosis
The diagnosis is possible with the identification of the clinical features associated with this condition after the birth. The prenatal diagnosis is also possible with the ultrasound during pregnancy as early as 14 weeks which can identify the associated abnormalities. The genetic testing can be used to confirm the diagnosis by detecting the genetic mutation responsible for developing this syndrome.
Treatment
There is no cure for Meckel syndrome at present and outcome is constantly fatal as the result of lung hypoplasia and renal failure. Genetic counseling can be beneficial for the affected families.
References
https://rarediseases.org/rare-diseases/meckel-syndrome/
https://ghr.nlm.nih.gov/condition/meckel-syndrome#inheritance
http://www.hfea.gov.uk/9085.html
