Introduction:
Lujan et al. described the combination of intellectual disability (ID) with marfanoid characteristics and male gender in 1984. It is an X-linked mental retardation disease caused by a missense mutation in the MED12 gene. It is unknown what the prevalence is in the general population. Clinical manifestations are the primary basis for the diagnosis. This condition has no known treatments. In this article, the Lujan-Fryns syndrome is discussed in more detail.
What Is Lujan-Fryns Syndrome?
Lujan-Fryns syndrome (LFS) is a rare condition characterized by intellectual incapacity, behavioral issues, and certain physical characteristics. It mainly affects men. A mutation in the MED12 gene primarily causes this condition. Mild to moderate mental retardation, significant facial dysmorphism (long, narrow face, short jaw, and prominent forehead), a tall, marfanoid stature, long, slender extremities, and behavioral issues are all associated with the syndrome. The underlying genetic defect is unknown. According to X-linked recessive inheritance, genetic counseling is provided. There is no particular prenatal testing available for this condition.
What Are the Other Names for Lujan-Fryns Syndrome?
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LFS.
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Lujan syndrome.
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XLMR with marfanoid features.
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X- linked mental retardation with marfanoid habitus.
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X- linked intellectual deficit with marfanoid habitus.
What Is the Epidemiology of Lujan-Fryns Syndrome?
Lujan-Fryns syndrome is rare, but its frequency in the general population is unknown. It mainly affects men and this condition is more prevalent in mentally challenged and psychiatric patients.
What Are the Causes of Lujan-Fryns Syndrome?
Lujan-Fryns syndrome is caused by at least one mutation in the MED12 gene. This gene gives directions for the production of a protein that aids in the regulation of gene activity and is involved in a variety of early developmental processes. The MED12 gene mutation that causes Lujan-Fryns syndrome alters a single protein building block (amino acid) in the MED12 protein. This genetic mutation changes the structure and functions of this protein. However, it is unknown how the mutation impacts development and results in Lujan syndrome's cognitive and physical characteristics.
What Is the Inheritance of Lujan-Fryns Syndrome?
This disorder has an X-linked recessive inheritance pattern. The gene responsible for this disease is found on the X chromosome, one of the two sex chromosomes. In males, one mutant copy of the gene is sufficient to cause the condition because they have one X chromosome only. Females need a mutation in both copies of the gene to develop the disease. Hence, it commonly affects males more than females because females have two copies of the gene. In addition, fathers cannot pass on X-linked features to their sons, a trait of X-linked inheritance.
What Are the Physical Features of Lujan-Fryns Syndrome?
Lujan syndrome is characterized by a tall, slender body and a large head (macrocephaly). Affected people also have a long, thin face with recognizable physical characteristics such as a prominent top of the nose (high nasal root), a short space between the nose and the upper lip (philtrum), a narrow roof of the mouth (palate), crowded teeth, and a small chin (micrognathia). In addition, nearly everyone who has this condition has a weak muscle tone (hypotonia).
Heart defects, genitourinary disorders, and poor speech may be the additional symptoms of Lujan syndrome. In addition, long fingers and toes with an unusually wide range of joint action (hyperextensibility) are common in those affected. People with this condition also experience seizures and abnormalities of the corpus callosum.
How to Diagnose Lujan-Fryns Syndrome?
The existence of clinical manifestations is used to make a diagnosis. There is no specific diagnostic test available. A cardiac examination and ultrasound, ophthalmologic examination, chromosomal analysis with special emphasis on chromosome 5pter and 22q11 (FISH- fluorescence in situ hybridization studies), and biochemical analysis of amino acids in plasma and urine are necessary to rule out a differential diagnosis.
What Is the Differential Diagnosis of Lujan-Fryns Syndrome?
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The chromosomal study is necessary because people with tall stature may have a chromosomal problem such as Klinefelter syndrome (47, XXY) or 47, XYY syndrome.
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FISH tests should rule out a 22q11 deletion syndrome (Shprintzen syndrome or velo-cardio-facial syndrome) in patients with nasal speech, thin extremities, and psychological disorders.
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DNA (deoxyribonucleic acid) analysis of the FMR1 gene should rule out Fragile-X syndrome (molecular investigation of the expansion of the CGG repeat in the FMR1 gene).
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Clinical and cardiologic examinations can rule out the autosomal dominant condition of Marfan syndrome, including checking the thorax's shape (pectus excavatum).
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Cardiac ultrasound should be performed to rule out an aortic aneurysm or dissection and quantify the aortic root diameter and mitral and aortic regurgitation.
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During an ophthalmologic examination, the eyes should be checked under a slit light to rule out myopia, ectopia lentis, and retinal detachment.
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Biochemical analysis of amino acids in plasma and urine can rule out homocystinuria in patients with tall stature, chest wall deformity, and lens dislocation.
How to Treat or Manage Lujan-Fryns Syndrome?
This condition has no specific treatment. Preventing severe scoliosis and developing orthopedic disorders should be prioritized. Regular checkups should be performed on patients with heart issues or epileptic convulsions. Patients require specialized instruction, psychological follow-up, and thorough neuropsychological testing. Special care should be taken to prevent aggressive outbursts and to identify early psychiatric problems such as psychosis.
Conclusion:
Lujan syndrome is one of the XLMR (X-Linked Mental Retardation) diseases that poses a significant diagnostic problem for medical and dentistry professionals. This condition does not have a particular treatment. Patients require special education and psychological follow-up, and emphasis should be given to the early diagnosis of psychiatric conditions. The current form of treatment is palliative therapy, which may include speech, behavioral, and special education. Yet, some steps can be taken to improve the person's quality of life. Attention to heart problems, seizures, and other potentially fatal disorders is important. It is possible to be prescribed a range of corrective, preventative, and intervention therapy.
