I want to briefly talk about the letter to the editor from Esra Demirci  (open-access) today and a continuation of some rather important research/clinical chatter about the inborn error of metabolism called phenylketonuria (PKU) intersecting with cases of autism (see here).
The author describes a case report of a child who was diagnosed with an autism spectrum disorder (ASD) "after performing a clinical assessment that included the Autism Behavior Checklist (ABC) and Childhood Autism Rating Scale (CARS)" and then subsequently diagnosed with PKU following some important metabolic investigations. They also highlight how instigation of a low phenylalanine diet - the treatment of choice for PKU - seemed to impact on the presentation of autism: "Eight months after the phenylalanine intake diet was initiated, he began to make eye contact, look when his name was said, and form two word sentences. His ABC scores fell from 57 to 46, and his CARS scores fell from 48 to 42."
The 'double syndrome' mentioned in the title of this post refers to the idea that there may be those on the autism spectrum who also have "an already described medical condition" and findings of autism and PKU comorbid fall into that category. I have to say that I'm a fan of this kind of thinking given the range of particularly metabolic conditions that do see to have 'an autistic element' to them (see here for another example). Screening is yet again implied (bearing in mind that PKU is already fairly routinely examined in all newborns in many countries). The idea, also yet again, that use of a low phenylalanine diet might also affect some of the signs and symptoms of autism in such cases remains a point for further investigation into hows and whys...
 Demirci E. Autism Spectrum Disorder and Phenylketonuria: Dyzygotic Twins with Double Syndrome. Noro Psikiyatr Ars. 2017 Mar;54(1):92-93.
Demirci E (2017). Autism Spectrum Disorder and Phenylketonuria: Dyzygotic Twins with Double Syndrome. Noro psikiyatri arsivi, 54 (1), 92-93 PMID: 28566968