Fragile X Syndrome, the most common cause of inherited mental retardation, results from mutation in fragile X mental retardation gene (FMR1) on long arm of X chromosome, Xq27.3. Clinical features include moderate to severe mental retardation without neurologic deficit, long face, large ears, prominent jaw, macro-orchidism, attention deficit, behavior disorder and occasionally autistic behavior . Hyperextensible joints     may also be seen in these patients. There is no other congenital
   malformation in fragile X syndrome.

          In this article we presented a 6 years old boy with fragile X syndrome who in addition to his characteristic clinical features had large thumbs and toes, which was disproportionate in size to his thumb nails and toe nails. In a case report from division of medical Genetics, Newyork Hospital in Cornell University, a twin brothers with fragile X syndrome also had cleft palate and ventricular septal defect . 

          The diagnosis of this case was performed by culturing the patient’s peripheral blood lymphocytes in media lacking folate which expose the fragile X sites. The chromosomal analysis was performed using G-banding.