Liver biopsy is how its found out for certain. Low energy, hypoglycemia, liver and kidney problems/failure eventually. If its completely absent fructose ingestion leads to death, usually infants completely lacking aldolase b will die after its first time consuming fructose. This condition is very rare, and likely not to concern you.
Good to know, thank you for sharing. I'm sorry that this has happened to you, is there any way to "fix" the deficiency as it sounds like it's a genetic abnormality? What is your diet like since finding this out?