Abdallat Davis Farrage syndrome is an extremely rare genetic condition that was first identified and described in 1980. It is characterized by pigmentation irregularities in the skin and nervous system problems. The condition is named for the team of medical professionals who first wrote it up, describing the appearance of the syndrome in a family from Jordan. It manifested in two brothers and a sister who were the children of first cousins who had married, suggesting a strong genetic link, and later testing did indeed reveal that the condition is genetic in nature.
This condition is a recessive trait, meaning that in order to manifest symptoms, someone must inherit a gene for Abdallat Davis Farrage syndrome from both parents. It is also autosomal, not linked to either of the genes that determine gender, so it can manifest in both men and women. People with only one gene are carriers, and they typically manifest no symptoms; in the event that someone inherits both genes, symptoms usually appear before one year of age.
A multitude of symptoms are associated with Abdallat Davis Farrage syndrome, but it is fundamentally classified as a form of phakomatosis, meaning that it is a disease of the central nervous system which is accompanied with skin abnormalities. It's also known as “neurocutaneous syndrome, Abdallat type,” referencing the neurological and skin problems associated with patients who have inherited both genes for the syndrome.
The skin problems associated with this condition include albinism, splotches or irregular pigmentation on the skin, and increased freckling. Many patients also exhibit unusual hair color, as part of the albinism. The central nervous system problems of Abdallat Davis Farrage syndrome patients cause them to experience extreme impairment in their extremities, including weakness in the arms and legs known as spastic paraparesis, and they tend to have a lack of sensitivity to pain, which can be problematic. Most experience peripheral neuropathy, a slow and steady degeneration of their peripheral nerves.
As yet, there is no treatment for Abdallat Davis Farrage syndrome. Care for patients usually focuses on keeping them comfortable and enabling them to live as normally as possible. Like other recessive traits, the condition can be brought out through intermarriage within an extended family. Many nations specifically ban such marriages for this very reason, and in regions where marriage within the family is not banned, people may want to think carefully about the consequences of a cousin marriage, as it greatly increases the risk for passing on dangerous genetic traits.