What type of biopsy is considered definitive for diagnosing GCA?

The temporal artery biopsy is considered the definitive method for diagnosing giant cell arteritis (GCA). This condition is characterized by inflammation of the temporal arteries, which can lead to serious complications like vision loss if not promptly recognized and treated. The biopsy involves extracting a small section of the temporal artery and examining it histologically for the presence of granulomatous inflammation, multinucleated giant cells, and other characteristic features of GCA.

This specific biopsy is particularly valuable because GCA can cause a segmental arterial involvement, meaning that inflammation may not be uniformly present along the entire length of the vessel. Therefore, the temporal artery is targeted as it is easily accessible and its inflammation is often reflective of the systemic condition. Other biopsy types, such as skin, muscle, or liver biopsies, do not provide the necessary information about the vasculitis affecting the temporal arteries specifically, making them less relevant in the context of diagnosing GCA.