Rosalind_UranianMoon
Makemake spent most of his life without help, so whenever he was sick, he'd often just ignore it or sleep the pain away.
Of course, after finding his found family, the people who actually care for him, there was no need for that anymore... right?
He didn't need to lie when he didn't feel good.
But what's the fun in that? He was the smartest one there after all... he could still deal with stuff like this on his own. He was independent!! He didn't need any help-
Or; Makemake hides the fact that he's sick from the people he loves, but due to the fact that people's personalities and actions often temporarily change for the worse when sick, which he didn't take into account, his friends find out anyways.