3 March 2021

Rheuma reasoning: giant cell arteritis

Clinical Rheumatology

A 75-year-old female presents with a four-week history of severe pain in the shoulder, pelvic girdle region and both hands.

She is unable to lift her arms in the air. Her hands are swollen and she is unable to do some basic daily care. Her mobility is impaired due to pain. 

Her pain has not been responsive to paracetamol or NSAIDs. She has been waking in the early hours of the morning and feels stiff most of the day. On closer questioning she has a global headache which has been present on most days, partially relieved with paracetamol. 

She has not paid much attention to this as her other pain is more dominant. She has rarely experienced a headache in her lifetime. She has not noted any jaw claudication. 

Her past history is notable for osteoporosis, with a lumbar spine T-score of -3.0, although she has not had a prior minimal trauma fracture. She has been on denosumab injections every six months for the last two years. She also has type 2 diabetes mellitus and takes metformin. She has no macrovascular or microvascular complications.

Examination shows synovitis in both wrists and multiple MCP joints and inability to make a fist. She cannot raise her hands above shoulder height. She is tender over the greater trochanters bilaterally and there is mild hip irritability. There is a small right knee effusion.  She is tender over the right side of the scalp and also has a sensation of scalp numbness. The temporal arteries are palpable and pulsatile.

ESR is raised at 72 (N<5), CRP is 64 (N<20). White cell count and platelets are raised. RF and CCP antibodies are negative. 

My initial concern is giant cell arteritis (GCA). She has clearly presented with an inflammatory condition given the peripheral joint swelling, raised CRP and ESR and predominance of morning stiffness. Her symptoms have both a polymyalgic presentation (hip and shoulder girdle pain) but there is also peripheral joint involvement. 

Jaw claudication is the most specific symptom for GCA. I often find the headache in GCA is not particularly severe, is often relieved temporarily by simple analgesia such as paracetamol, but is always recurrent. It is not always localised to the temporal region, despite the moniker of temporal arteritis.  

I immediately start her on prednisone 50mg daily. I typically use a dose of 1mg per kilogram up to 50mg daily, unless there are visual complications, where an admission to hospital for intravenous methylprednisolone is indicated. The gold standard diagnostic procedure is still a temporal artery biopsy. This should be done within two weeks of starting prednisone. A delayed temporary biopsy could yield a false negative result. 

The feared complication of sudden onset visual loss usually occurs prior to the use of prednisone, thus I start prednisone as soon as I contemplate this diagnosis. However, it is imperative there is urgent referral for specialist involvement and diagnostic investigation.  

There has been a recent push to utilise other non-invasive diagnostic tools for giant cell arteritis. These methods may involve ultrasound of the temporal arteries, CT or MR angiography or PET scanning. Very few centres have the necessary skills or experience to accurately use ultrasound to diagnose GCA. A PET scan can be useful to assess for large vessel uptake away from the cranium; however, a PET scan is not funded on the PBS for this indication and it must still be performed soon after starting prednisone. Hence a temporal artery biopsy is still the diagnostic procedure of choice in most situations. 

A right-sided temporal artery biopsy was performed. The biopsy confirms GCA with an inflammatory infiltrate in the intima and media and disruption of the internal elastic membrane. Ideally a 20-30mm sample should be obtained as there can be skip lesions and a longer biopsy will be more likely to provide a true result. Her headache and polymyalgia symptoms completely resolve within a few days of starting prednisone. 

The main challenge in managing GCA is the morbidity associated with the long-term high doses of prednisone. The patient population is usually older and frequently have pre-existing comorbidities. In her situation, osteoporosis and type 2 diabetes mellitus are concerning comorbidities which complicate the management. 

Tocilizumab (IL-6 inhibitor) has recently received PBS approval for treatment of giant cell arteritis if certain criteria are met. The main benefit of using tocilizumab is it allows a more rapid type of prednisone and this avoids some of the morbidity associated with high doses of prednisone.  With her comorbidities, I thought tocilizumab would help minimise steroid side-effects. Tocilizumab is a weekly subcutaneous injection. It nearly always induces normal ESR and CRP due to its mechanism of action. If I am using tocilizumab, I aim for a taper of prednisone to 10mg daily over six to eight weeks. This compares with my usual target of reducing prednisone to around 20mg over the course of three months if prednisone monotherapy is used. 

Methotrexate has weak evidence as a mild steroid-sparing agent in GCA, although it does not allow such a rapid taper of prednisone as tocilizumab. The use of aspirin is controversial and PPI cover should be given if there is co-administration of aspirin and prednisone. 

Most people diagnosed with GCA are over the age of 60 years and will need some form of bone protection given the high doses of prednisone. I always utilise calcium and vitamin D supplementation, aiming for vitamin D3 level of greater than 60. If bone mineral density scans show a T-score lower than -1.5 then I will use an anti-resorptive agent such as denosumab or zoledronic acid, however denosumab is not funded under the PBS for steroid-induced osteoporosis.

GCA is a chronic condition requiring long-term immunosuppression. The main challenge in this condition is minimising treatment complications in an age group who frequently have comorbidities and are susceptible to steroid-induced side-effects.

Dr Andrew Jordan is a rheumatologist based in Parramatta, Sydney, with a special interest in inflammatory arthritis, gout and PRP injections

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