OMIM ID:
Microphthalmia, Syndromic 9
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Both microphthalmia and clinical anophthalmia have been described in this syndrome. However, autopsy has shown true anophthalmia in a few cases who were stillborn or died in the neonatal period. At least one eye can be cystic. The optic nerves are often hypoplastic and may be absent. High, upward-arching eyebrows may be seen.
Systemic Features
An early manifestation of this disorder is neonatal pulmonary distress. The lungs are usually hypoplastic or malformed. Cardiac malformations such as patent ductus arteriosus, septal and valvular defects, tetralogy of Fallot, and single ventricles are often present. Diaphragmatic hernias or defects are common but hiatal hernias and frank eventration of abdominal contents have also been reported. Renal anomalies and intrauterine growth retardation have been noted.
Some infants have micrognathia, low-set ears, a broad nasal bridge, brachycephaly, and midline clefts of the palate. Cerebral malformations are seldom present.
Genetics
Inheritance
Homozygous mutations in the STRA6 gene (15q24.1) have been found in a few cases which suggests autosomal recessive inheritance. Parental consanguinity has been reported in some families.
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.