In a newly published study, parents of patients with fragile X syndrome surveyed during  a 3-month course of treatment with an antibiotic commonly prescribed to treat adolescent acne reported increased attention spans and communication, and decreased anxiety in their children.

Fragile X syndrome is a genetic disorder, the result of a defect on the X chromosome. It is estimated to affect 1 in 3,600 males and 1 in 4,000 females. One-third of all children with fragile X syndrome develop autism and approximately 5 percent of children with an autism-spectrum disorder have fragile X.

Minocycline, the antibiotic used in the placebo-controlled study, is one of the most commonly prescribed medications for adolescent acne and has been in use since the 1960s.

The study, "Minocycline Treatment in Patients with Fragile X Syndrome and Exploration of Outcome Measures" is published in the September 2010 issue of the American Journal of Intellectual and Developmental Disabilities.

For the study, Randi Hagerman, MD, Fragile X Endowed Chair, medical director of the University of California-Davis MIND Institute and one of the world's leading experts on fragile X syndrome, prescribed minocycline to patients at the Fragile X Research and Treatment Center at the MIND Institute. Other participants were treated elsewhere by their primary-care physicians.

The study included a total of 53 patients, three of whom dropped out after a few days because of side effects. The remaining 50 participants, seven females and 43 males, took the drug for between 2 weeks and 20 months, with dosages of 25-200 mg per day. Participants ranged in age from 4 months to 25 years.

Fifty-four percent of the participants' parents said their children showed improvements in their use of language. Fifty percent said their children's attention spans improved. Forty-four percent said their children's social communication improved. And 30 percent said their children's anxiety levels decreased.

In anecdotal reports, parents said that after taking minocycline their children used more language, had clearer speech and were more understandable. Some said their children were "becoming more conversational, articulate and talkative," the study states. Parents also reported their children were more focused and "had longer attention spans when playing, doing homework or participating in another activity."

Most parents said their children experienced mild side effects, such as an upset stomach. Hagerman also wanted to learn whether the patients would experience the tooth discoloration common to individuals using tetracyclines; reports of those side effects were minimal.

Interest in using minocycline in human patients with fragile X surged after a 2009 study found minocycline improved cognition in mice genetically engineered to have fragile X. That study's senior author was Iryna M. Ethell of the Univeristy of California-Riverside, who also is an author in the Hagerman-led research.

Ethell and her colleagues found minocycline lowers the levels of matrix metalloproteinase 9 (MMP9), an enzyme present in the normal brain whose levels and activity are over-expressed in the fragile X mouse. MMP9 inhibits development of structures called dendritic spines, tiny mushroom-like projections at the ends of synapses /that allow neural cells to communicate. Lowering the amount and activity of MMP9 strengthens the dendritic spines and improves the establishment and maintenance of circuits in the brain.