OMIM ID:
Manitoba Oculotrichoanal Syndrome
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
The ocular phenotype has not been completely defined because of the limited number of families reported. Colobomas, unilateral and bilateral, of the upper eyelids seems to be the most consistent finding. Clinical hypertelorism is also a common finding. Nasolacrimal duct obstruction, unilateral clinical anophthalmia, cryptophthalmos, and a cloudy cornea have also been reported.
Systemic Features
The anterior scalp hairline is abnormally low, sometimes extending to the eyebrows. The anus is anomalous and may be stenotic in some cases. The nasal tip is often broad and has a notch. Several patients had omphaloceles.
Genetics
Inheritance
Autosomal recessive inheritance has been assumed as no direct transmission from parent to child has been reported, and most affected individuals (including sibs) have been found in an isolated population of Manitoba Indians with a high rate of consanguinity. Homozygous deletions of exons 8-23 in FREM1 as well as simple 4bp deletions (9p22.3) have been found in several families confirming the presumed autosomal recessive mode of inheritance.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.