Luke became his mother's caregiver after she lost her job to what her doctors thought was schizophrenia. He kept detailed records of what she ate and drank, and organized her clothing for her. He usually accompanied her to social services offices and made sure her bills were paid. He usually lied and said he was 18 when anyone asked. When someone asked who was Lucy's dependent listed on her forms, he said it was his younger brother.
At one trip to social services, Luke gave his mother some alcohol to calm her. However, she soon after collapsed due to a deep vein thrombosis. He accompanied her to the hospital where Dr. Wells told him that he thought the deep vein thrombosis was due to alcoholism. However, Luke denied this could be the case as he monitored her alcohol intake. Dr. Wells discounted his explanation, but Gregory House overheard the conversation and chipped in to ask Dr. Wells if he had checked for other signs of alcoholism. It was obvious that Dr. Wells hadn't, but he resented House interfering in his case. Dr. House agreed to take the case and took Luke's copious notes to his team and told them the notes could be trusted.
Dr. House soon realized that Lucy could be suffering from Vitamin K deficiency. When an environmental scan showed that Lucy had been eating nothing but frozen hamburgers which lacked Vitamin K, Luke felt very guilty. Dr. House told him that he shouldn't be blaming himself, and also confronted him about his age, guessing that Luke was about 15 and using growth plates in his leg as the reason he thought that. Luke was bluffed out and admitted he was only 15. House agreed not to rat him out.
However, Lucy was also found to be suffering from liver cancer. While she was recovering from risky but successful surgery, child services showed up to remove Luke from her custody. Luke blamed House, but House knew he hadn't done it. A little detective work found that Lucy had phoned child services from her room. This intrigued House as such a decision would be atypical for a schizophrenic. He started to dig deeper into her medical history and found one of her last appointments had been with an opthamologist. After discussing it with his team, Allison Cameron suggested Wilson's disease, which was confirmed when Kaiser-Fleischer rings were found in her iris. She was treated for it and soon recovered. Soon after, she was reunited with Luke.
Luke confronted House about ratting him out, and House took responsibility, claiming he did it because he was tired of Luke. Lucy smiled quietly in gratitude.