While there is no specific treatment for the underlying genetic cause of LFS; corrective procedures, preventive intervention measures and therapies may be considered in the treatment and management of the many craniofacial, orthopedic and psychiatric problems associated with the disorder. More pressing issues such as cardiac involvement or epileptic seizures should be routinely examined and monitored. Close attention and specialized follow-up care, including neuropshycological evaluation methods and therapies, and special education, should be given to diagnose and prevent psychiatric disorders and related behavioral problems such as psychosis and outbursts of aggression.

FG syndrome (FGS; also known as Opitz–Kaveggia syndrome) is a rare genetic syndrome caused by one or more recessive genes located on the X chromosome and causing physical anomalies and developmental delays. FG syndrome was named after the first letters of the surnames of the first patients noted with the disease. First reported by Opitz and Kaveggia in 1974, its major clinical features include intellectual disability, hyperactivity, hypotonia (low muscle tone), and a characteristic facial appearance including macrocephaly (an abnormally large head).

Lujan–Fryns syndrome (LFS), also referred to as X-linked mental retardation with Marfanoid habitus and Lujan syndrome, is an X-linked genetic disorder that causes mild to moderate intellectual disability and features described as Marfanoid habitus, referring to a group of physical characteristics similar to those found in Marfan syndrome. These features include a tall, thin stature and long, slender limbs. LFS is also associated with psychopathology and behavioral abnormalities, and it exhibits a number of malformations affecting the brain and heart. The disorder is inherited in an X-linked dominant manner, and is attributed to a missense mutation in the "MED12" gene. There is currently no treatment or therapy for the underlying "MED12" malfunction, and the exact cause of the disorder remains unclear.

FG syndrome's major clinical features include intellectual disability, usually severe; hyperactive behavior, often with an outgoing personality; severe constipation, with or without structural anomalies in the anus such as imperforate anus; macrocephaly; severe hypotonia; a characteristic facial appearance due to hypotonia, giving a droopy, "open-mouthed" expression, a thin upper lip, a full or pouting lower lip, and partial or complete loss of the corpus callosum. About a third of reported cases of individuals with FG syndrome die in infancy, usually due to respiratory infection; premature death is rare after infancy.