"We report a case of a 5-year-old patient with autism, who presented with scurvy secondary to the dietary restrictions of a ketogenic diet."
That was the aim of the paper by Syed Amir Ahmad and colleagues  who continue an important theme in autism research and clinical practice circles pertinent to the seeming over-representation of illnesses of malnutrition in relation to autism (see here).
The 'value added' bit to the Ahmad findings is the observation that scurvy - a disease caused by insufficient vitamin C in the diet - was seemingly present as a result of "the dietary restrictions of a ketogenic diet" (where a ketogenic diet represents a high fat, low carbohydrate eating schedule). I assume said diet was put in place in light of some previous research suggesting that a ketogenic diet (KD) may be 'useful' for some children on the autism spectrum (see here and see here) from a behavioural perspective or where indicated following the detection of an inborn error of metabolism for example.
Scurvy is something of a pet topic on this blog (see here and see here). Described as a rare disease, the growing [research] literature on autism and scurvy indicates that it is perhaps not as rare as many people think or would like it to be. One of the big issues in this area is that more screening needs to be done for scurvy in relation to a diagnosis of autism, particularly when children (and adults) on the autism spectrum might have a limited or restricted diet (see here).
"This case emphasizes the importance of vitamin supplements in patients consuming a special diet." I wholeheartedly agree with that conclusion made by the authors. I say this in the context that supplementation with various vitamins, minerals and nutrients where autism is present and a 'special diet' is being followed is already a good idea (see here). The fact that some of those nutrients being supplemented might themselves have an 'effect' of on the behaviour of some children (see here and see here for examples) is also something important to mention.
the bottom line: screen and keep screening for health issues like scurvy when autism is diagnosed.
 Ahmad SA. et al. Florid Scurvy in an Autistic Child on a Ketogenic Diet. Pediatr Emerg Care. 2018 Nov 19.