The language of the autopsy suggests that starvation and stress caused a perforation in the upper gastrointestinal tract. The ulcer developed [or if it was preexisting, was aggravated] in the duodenum, the upper area of the small intestine, not the stomach. There are also differences between the causes of stomach ulcers and duodenal ulcers.
The autopsy seems to contradict itself by referring to starvation and stress as the cause of death. Wasn’t the mechanism of death from internal bleeding caused in turn by starvation and stress? This may seem like arguing over semantics, but starvation in general is seldom seen as a cause of death.
What we can say is there appears to be a relationship between endocrine disorders and holoprosencephaly. Thus the answer to the question appears to be that Nora did have a pre-exisiting condition. Medical history is likely to confirm this, along with a prescribed medical maintenance program. Nora’s parents ought to be in a position to confirm medical treatment in this regard. Hopefully further information in this area will be forthcoming.