Causes
Fragile X syndrome is a genetic disorder which occurs as a result of a mutation of the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene on the X chromosome, most commonly an increase in the number of CGG trinucleotide repeats in the 5 untranslated region of FMR1. Mutation at that site is found in 1 out of about every 2000 males and 1 out of about every 259 females. Incidence of the disorder itself is about 1 in every 3600 males and 1 in 4000–6000 females. Although this accounts for over 98% of cases, FXS can also occur as a result of point mutations affecting FMR1.In unaffected individuals, the FMR1 gene contains 5–44 repeats of the sequence CGG, most commonly 29 or 30 repeats. Between 45 and 54 repeats is considered a "grey zone", with a premutation allele generally considered to be between 55 and 200 repeats in length. Individuals with fragile X syndrome have a full mutation of the FMR1 allele, with over 200 CGG repeats. In these individuals with a repeat expansion greater than 200, there is methylation of the CGG repeat expansion and FMR1 promoter, leading to the silencing of the FMR1 gene and a lack of its product. This methylation of FMR1 in chromosome band Xq27.3 is believed to result in constriction of the X chromosome which appears fragile under the microscope at that point, a phenomenon that gave the syndrome its name. One study found that FMR1 silencing is mediated by the FMR1 mRNA.
Other uses
Risperidone has shown promise in treating therapy-resistant obsessive-compulsive disorder, when serotonin reuptake inhibitors alone are not sufficient.Risperidone has proven to be effective in treatment with Attention deficit hyperactivity disorder especially in cases of aggression or with another mental condition.Risperidone has not demonstrated a benefit in the treatment of eating disorders or personality disorders, except for limited evidence in schizotypal personality disorder. Forms
Available forms of risperidone include tablet, oral dissolving tablet, oral solution, and powder and solvent for suspension for injection. Adverse effects
Common side effects include movement problems, sleepiness, dizziness, trouble seeing, constipation, and increased weight. About 9 to 20% of people gained more than 7% of the baseline weight depending on the dose. Serious side effects may include the potentially permanent movement disorder tardive dyskinesia, as well as neuroleptic malignant syndrome, an increased risk of suicide, and high blood sugar levels. In older people with psychosis as a result of dementia, it may increase the risk of death.While atypical antipsychotics appear to have a lower rate of movement problems as compared to typical antipsychotics, risperidone has a high risk of movement problems among the atypicals. Atypical antipsychotics, however, are associated with a greater amount of weight gain and other metabolic side effects. Drug interactions
Carbamazepine and other enzyme inducers may reduce plasma levels of risperidone. If a person is taking both carbamazepine and risperidone, the dose of risperidone will likely need to be increased. The new dose should not be more than twice the patients original dose.