Fragile X Syndrome and Periventricular Heterotopias: A Rare Association

Fragile X syndrome (FXS) is the most common hereditary cause of intellectual disability in males, with an estimated prevalence of 1:4000. Epilepsy occurs in 10 to 20% of males with FXS and usually has a favorable prognosis and positive response to antiepileptic medication. Numerous anomalies in the central nervous system have been reported in FXS. Among these, periventricular heterotopia (PH) has been reported in two previous cases. Epilepsy is also a common comorbidity in PH, but in contrast to epilepsy in FXS, the severity may vary markedly. We present a boy with FXS, PH, and epilepsy—a combination not previously reported in the literature. The presented case suggests a necessity to consider PH in cases of refractory epilepsy or status epilepticus in patients with FXS, emphasizes the importance of ruling out FXS in children with intellectual disability even if there are only discreet or no clinical signs of the disorder, and underscores that FXS should be considered in patients with PH if no other cause can be found.