Which fictional specialty did House lead at Princeton-Plainsboro in House M.D.?

House led the fictional Department of Diagnostic Medicine at Princeton-Plainsboro Teaching Hospital.

The department handles unusually complicated cases that other physicians have been unable to solve. House and his fellows assemble clues from symptoms, medical histories, tests, and sometimes risky procedures to identify a disease or condition.

Diagnostic medicine is a real medical activity, but House’s department is portrayed more dramatically and independently than most real-world hospital structures. In practice, difficult diagnoses commonly involve collaboration among multiple specialties rather than one small team operating as a separate mystery-solving unit.

The department’s membership changes repeatedly throughout the series. Early team members include Robert Chase, Allison Cameron, and Eric Foreman, while later seasons introduce other physicians. House himself is also associated with nephrology and infectious disease, but those are his personal specialties; the department he leads is Diagnostic Medicine.