An 8-year-old boy bleeds excessively after tooth extraction, and his partial thromboplastin time (PTT) is prolonged, corrected by hemophilia A plasma. What is the likely diagnosis?

The details provided in the scenario suggest a diagnosis of Hemophilia A. This condition arises from a deficiency in clotting factor VIII, which is critical in the coagulation cascade. The boy's excessive bleeding after tooth extraction is indicative of a bleeding disorder. The prolonged partial thromboplastin time (PTT) points towards a problem in the intrinsic pathway of coagulation, where factor VIII plays a vital role.

The correction of the PTT by hemophilia A plasma further supports the diagnosis, as administering plasma containing factor VIII would restore normal coagulation in a patient with Hemophilia A. The fact that the PTT corrects indicates that the underlying issue relates specifically to a deficiency of factor VIII, as adding that factor compensates for the lacking component.

In contrast, other conditions listed in the options are associated with different deficiencies or coagulation pathways. Therefore, the scenario strongly aligns with the characteristics of Hemophilia A, confirming it as the likely diagnosis.