The condition - caused by drinking alcohol during pregnancy - means he has uncontrollable outbursts of rage and is incredibly sensitive to the slightest changes to his routine or environment.
Amanda Clegg, who adopted Isaac five years ago, said even the weather turning from sun to rain can cause a meltdown.
“Everything in his life has to be perfect for him to manage,” she said. “We have to think three steps ahead, 24/7 but there are always other factors that we can’t predict, like the weather or other people.
“It’s an invisible disability. He can hold it together for so long but what people don’t realise is that his brain is going 100mph all the time. He can go from laughing and joking with you and the next moment he can be in full blown crisis mode and exploding with anger.”
She and Isaac are sharing their experiences in a bid to raise more awareness of FASD, which Amanda says seems rarely known about.
She has even had to explain the condition to some health professionals.
She also wants to make more women aware of the risks of drinking in pregnancy.
“Everybody thinks you have to be alcohol dependent during pregnancy but you don’t - it can be a glass of wine with your meal on a Saturday,” she said. “You’re playing Russian roulette with your baby’s brain.”
Amanda praised Warley Town School, where Isaac is in Year 2, and King Cross Park RLFC, where Isaac plays, for being “brilliant” with her little boy.
For more about FASD, click here.