PMR & Giant Cell Arteritis

Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are linked inflammatory conditions of adults over 50: PMR causes girdle pain and stiffness, and GCA is a large-vessel vasculitis that can cause irreversible visual loss.

Around 50% of people with GCA have PMR features, and around 15% of people with PMR develop GCA. Suspected GCA is a medical emergency and is treated the same day.

Masters athletes and older event populations may present pitchside.

Both conditions are T-cell driven inflammatory responses in genetically susceptible people (HLA-DR4, northern European ancestry), with different targets.

• •PMR: bursitis and synovitis around the shoulders (subacromial and subdeltoid bursitis, biceps tenosynovitis) and hips (trochanteric and iliopsoas bursitis). The pain comes from these structures, not from muscle, despite the name.
• •GCA: granulomatous inflammation of large and medium arteries, starting in the adventitia. Multinucleated giant cells form in the media, the internal elastic lamina is disrupted and intimal hyperplasia narrows the lumen.

Interleukin-6 (IL-6) drives the systemic response and is the target of tocilizumab. Visual loss comes from posterior ciliary artery occlusion, causing anterior ischaemic optic neuropathy (AION): sudden, painless and irreversible, with the other eye at risk. It occurs in around 15% to 20% of untreated GCA and is largely preventable with prompt steroids.