Some of these mutations include a 1-base pair duplication in exon 4, a 2-base pair insertion in exon 2, a 1-base pair deletion in exon 4, and a 329-base pair deletion in exon 4 of the gene. The above mutations cause a frameshift in the gene. A frameshift mutation refers to a condition in which the reading frame of the gene is disrupted by the insertion or deletion of base pairs from the gene (if the number of inserted or deleted base pairs is not divisible by three). This frameshift mutation ultimately results in a premature termination codon (the formation of a termination codon at a position more "forward" than normal). Other mutations include a base pair transition in the start codon, which is the starting site of translation of the gene. A transition mutation occurring at this codon disrupts the codon sequence and abolishes the site. This prevents the cell from carrying out translation of the gene. Diagnosis
The diagnosis of Filippi Syndrome is mostly done postnatally. Initial diagnosis of the disease relies on clinical observation of symptoms, including different degrees of syndactyly and craniofacial abnormalities, exhibited by affected individuals. Diagnosis can also be done through radiography, which checks for malformation of digits.Confirmation of diagnosis requires the use of genetic testing.
Brachydactyly is believed to be largely due to abnormalities arising from the bones inside the hands and feet, specifically the metacarpals and metatarsals. Craniofacial abnormalities
Furthermore, most people with Filippi Syndrome exhibit craniofacial abnormalities. Craniofacial abnormalities are birth defects observed at the head or face region of affected individuals. Some of the craniofacial abnormalities present in people with Filippi Syndrome include microcephaly (having a skull that is smaller than normal), prominent/ elevated nasal bridge, hypertelorism (having ones pair of eyes further apart from each other than normal), and underdeveloped nasal alae (underdeveloped tissues surrounding the nostril). Less common craniofacial abnormalities include having a broad forehead, thin vermilion border (having a thin upper lip), and frontal hirsutism (having a hairy forehead). Mental retardation
People with Filippi Syndrome may also demonstrate varying degrees of intellectual disability. Affected individuals may experience defective speech development, aphasia (experiencing difficulty in finding the appropriate words to use), vision impairment, and an inability to speak. Growth retardation
Another characteristic symptom of people with Filippi Syndrome is the occurrence of growth retardation, which is also referred to as growth delay. Such growth delays may be either prenatal or postnatal, meaning that they can occur both before and after birth. In particular, delayed bone maturation can be observed in patients with Filippi Syndrome. Other symptoms
People with Filippi Syndrome may exhibit some other physical abnormalities.