Interstitial deletions of chromosome band Xq26.3 are rare. We report on a 
2-year-old boy in whom array comparative genomic hybridization analysis revealed 
an interstitial 314 kb deletion in Xq26.3 affecting SLC9A6 and FHL1. Mutations 
in SLC9A6 are associated with Christianson syndrome (OMIM 300243), a syndromic 
form of X-linked mental retardation (XLMR) characterized by microcephaly, severe 
global developmental delay, ataxia and seizures. FHL1 mutations cause 
Emery-Dreifuss muscular dystrophy (OMIM 310300), X-linked myopathy with postural 
muscle atrophy (XMPMA, OMIM 300696), scapuloperoneal myopathy (OMIM 300695), or 
reducing body myopathy (OMIM 300717, 300718). The clinical problems of the 
patient reported here comprised severe intellectual disability, absent speech, 
ataxia, epilepsy, and gastroesophageal reflux, and could mostly be attributed to 
SLC9A6 insufficiency. In contrast to the majority of reported Christianson 
syndrome patients who were microcephalic, this patient was normocephalic, but 
his head circumference had decelerated from the 50th centile at birth to the 
25th centile at the age of 2 ²/¹² years. Muscle problems due to the FHL1 
deletion are not to be expected before late childhood, which is the earliest age 
of onset for FHL1 associated Emery-Dreifuss muscular dystrophy. This patient 
broadens the spectrum of SLC9A6 mutations and contributes to the clinical 
delineation of Christianson syndrome. This is also the first patient with a 
deletion affecting both SLC9A6 and the complete FHL1 gene.