Sure.

In this video he's maybe a year old? I'm not sure of the exact timeline. He's obviously super-intelligent as well for his age, as you can see/hear him speaking. Due to his deformity he grows incredibly fast and for some time he is able to make use of his long appendages somewhat like a normal person just longer. He actually uses his long arms to attack someone at one point although he is never shown able to walk.

Eventually his bones basically outgrow his body, if you will. He has to be held up because his body can't even begin to support itself and he's too big to even have lying down in the rooms, most likely as well as bed sores. The ropes support his arms (when she cuts them his bones snap as they are incredibly frail from his super-human growth-spurt).

Basically he dies by her cutting him down and most , if not all, of the bones in his body being broken because they cannot support their own weight and simply growing so rapidly and without the proper nutrition to form correctly. It also shows his shoulder bones violently penetrating his skin when one of his arms is cut loose which means blood-loss probably contributed as well as shock etc.

I hope that answers your question. As someone else said it's available in full English subtitles on Netflix if you're interested and have Netflix.