Madam Chen,who calls her son Ah Qiang, said: "Ah Qiang was born a mute. When he was growing up, I kept pushing him to call me 'ma', but he never opened his mouth. That broke my heart."
Ah Qiang has been unable to walk since he suffered a polio attack when he was a toddler.
He can only limp with Madam Chen's help.
Being unable to walk to the toilet also means Ah Qiang defecates wherever he is.

Madam Chen worries that her son may fall if he tries to stand. Because of this, she watches over him whenever she can.
Her other child, a daughter, moved out of the family's three-room flat in Ang Mo Kio after getting married years ago.
Madam Chen's greatest fear is that no one will be around to look after Ah Qiang after she dies.
Her husband, 70, has been bedridden since a stroke a few months ago.
He stopped working as a cleaner and the family now gets by with handouts from relatives.
Her husband's illness also means she is now burdened with caring for two men.

Husband bedridden

Besides looking after Ah Qiang, Madam Chen also has to feed and clean her husband.
She is not in robust health herself - her legs are swollen, making housework painful for her. Yet she soldiers on, attending to her son's needs.
When Lianhe Wanbao met mother and son, Madam Chen kept gazing lovingly at Ah Qiang.
She said: "He has been suffering since his birth. As a mother, the only thing I can do for him is to look after him. It's hard on me, but I don't mind."