Meckel syndrome

Meckel syndrome
Classification and external resources
Specialty
ICD-10	Q61.9
OMIM	249000
DiseasesDB	31661
eMedicine	ped/1390
Patient UK	Meckel syndrome

Meckel syndrome (also known as Meckel–Gruber Syndrome, Gruber Syndrome, Dysencephalia Splanchnocystica) is a rare, lethal, ciliopathic, genetic disorder, characterized by renal cystic dysplasia, central nervous system malformations (occipital encephalocele), polydactyly (post axial), hepatic developmental defects, and pulmonary hypoplasia due to oligohydramnios.

Meckel–Gruber syndrome is named for Johann Meckel and Georg Gruber.

Diagnosis

Dysplastic kidneys are prevalent in over 95% of all identified cases. When this occurs, microscopic cysts develop within the kidney and slowly destroy it, causing it to enlarge to 10 to 20 times its original size. The level of amniotic fluid within the womb may be significantly altered or remain normal, and a normal level of fluid should not be criteria for exclusion of diagnosis.

Occipital encephalocele is present in 60% to 80% of all cases, and post-axial polydactyly is present in 55% to 75% of the total number of identified cases. Bowing or shortening of the limbs are also common.

Finding at least two of the three phenotypic features of the classical triad, in the presence of normal karyotype, makes the diagnosis solid. Regular ultrasounds and pro-active prenatal care can usually detect symptoms early on in a pregnancy.

Pathophysiology

This condition is inherited in an autosomal recessive pattern, meaning two copies of the gene in each cell are altered

Meckel–Gruber syndrome (MKS) is an autosomal recessive lethal malformation. Recently, two MKS genes, MKS1 and MKS3, have been identified. A study done recently has described the cellular, sub-cellular and functional characterization of the novel proteins, MKS1 and meckelin, encoded by these genes. The malfunction of this protein production is mainly responsible for this lethal disorder.

Type	OMIM	Gene
MKS1	609883	MKS1
MKS2	603194	TMEM216
MKS3	607361	TMEM67
MKS4	611134	CEP290
MKS5	611561	RPGRIP1L
MKS6	612284	CC2D2A
MKS7	608002	NPHP3
MKS8	613846	TCTN2
MKS9	614144	B9D1
MKS10	611951	B9D2

Relation to other rare genetic disorders

Recent findings in genetic research have suggested that a large number of genetic disorders, both genetic syndromes and genetic diseases, that were not previously identified in the medical literature as related, may be, in fact, highly related in the genetypical root cause of the widely varying, phenotypically-observed disorders. Thus, Meckel–Gruber syndrome is a ciliopathy. Other known ciliopathies include primary ciliary dyskinesia, Bardet–Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alstrom syndrome, and some forms of retinal degeneration. The MKS1 gene has been explicitly identified as a ciliopathy.

Incidence

While not precisely known, it is estimated that the general rate of incidence, according to Bergsma, for Meckel syndrome is 0.02 per 10,000 births. According to another study done six years later, the incidence rate could vary from 0.07 to 0.7 per 10,000 births.

This syndrome is a Finnish heritage disease. Its frequency is much higher in Finland, where the incidence is as high as 1.1 per 10,000 births. It is estimated that Meckel syndrome accounts for 5% of all neural tube defects there.