They destroy themselves physically.  They neglect their own health to care for the ill child.  They don't go to the doctor for themselves because they can't afford even a reasonable copay and deductible for themselves; every cent has to go to the child.  They take on second jobs, or they come home from their paid jobs to start a second shift as unpaid and untrained caregivers because there is no money to pay a professional and insurance seldom if ever covers this cost anywhere near as long or as often as needed.  They sacrifice sleep.  They eat cheap, nutrient-poor food in order to pay for the child's medication.

They destroy themselves emotionally.  They have to beg, beg, beg for money all the time.  I understand that in some countries parents don't have to put their children's photos on empty mayonnaise jars at grocery store cash registers in order to pay the oncologist--not that this ever really pays the  oncologist; it just slows the inevitable descent into poverty.  They have to pour so much of their time and attention into the ill child, since paid help is out of the question except for the rich, that the other children tend to be neglected.  They may work opposite shifts so somebody is always at home, but they can seldom just sit and talk as a couple, so the marriage suffers.

Having a seriously ill or impaired child can drag a whole family into poverty and break up a household.  All because socialism is such a dirty word here.

ETA:  As I'm sure you've noticed, the same people who scream about socialism invading and making us . . . all live without fear of dying due to lack of money, which is somehow . . . evil . . . or something, I dunno--anyway, they also like to rant and rave about lazy poors living high on the government hog.  So you not only go down in the slow-motion landslide of poverty in order to save your child's life and/or keep her out of an underfunded institution, but you also get rocks thrown at you all the way down.