In hemophilia, how is the Partial Thromboplastin Time (PTT) affected?

In hemophilia, the Partial Thromboplastin Time (PTT) is significantly affected due to the underlying issues with the blood's clotting ability. Hemophilia is a genetic disorder characterized by a deficiency in certain clotting factors, commonly factors VIII (hemophilia A) or IX (hemophilia B). These factors are crucial for the intrinsic pathway of the coagulation cascade.

When there is a deficiency or absence of these factors, the intrinsic pathway is impaired, leading to a prolonged PTT. This reflects the time it takes for blood to clot through this pathway. Thus, in individuals with hemophilia, the PTT is expected to increase, indicating that the coagulation process is taking longer than normal due to the dysfunction in the clotting factors.

In contrast, conditions that do not affect the intrinsic pathway would not alter the PTT, nor would an increase be expected if there were normal functioning of the clotting factors involved. The increase in PTT is a key diagnostic indication when assessing for hemophilia in a patient presenting with bleeding tendencies.