Which fictional medical specialty did House's department represent in House M.D.?

House's department in House M.D. was Diagnostic Medicine.

The Department of Diagnostic Medicine investigates difficult cases that remain unexplained after routine tests and consultations. Gregory House leads a small team of doctors who combine specialties, review evidence, and repeatedly revise their working diagnosis. The department is a fictionalized television device, but it draws on real clinical practices such as differential diagnosis and consultation among specialists.

The show often begins with an apparently simple illness that develops unexpected symptoms. House's team proposes several possibilities, orders tests, and responds to new information. This structure gives the series its medical-mystery format and lets the doctors use knowledge from neurology, immunology, infectious disease, cardiology, and other fields.

Diagnostic medicine should not be confused with a single conventional specialty such as neurology. House himself is described as a diagnostician with specialties in infectious disease and nephrology, while his department draws on the broader process of solving unexplained medical cases.