House observes the sisters in their shared room. He notices that while they look identical, Maya (the one with lung failure) has a slightly different callus on her finger. He realizes she isn't just a gymnast; she’s a secret smoker. But that doesn't explain Lea's seizures.
: House’s team (Chase, Cameron, and Foreman) is stymied. Because they are monozygotic triplets, any genetic defect should be present in all three. However, their bodies are reacting differently to the same environment. Dr. House: 2Г—3
: House treats them as a single organism with three different "outputs." He theorizes that while their DNA is the same, their epigenetics —how those genes are expressed—have diverged due to secret lifestyle differences. House observes the sisters in their shared room
The title refers to a high-stakes medical mystery where Dr. Gregory House must solve a case involving a set of triplets whose identical DNA makes diagnosing their divergent symptoms a nightmare . The Case of the Mirror Triplets But that doesn't explain Lea's seizures