19. A case of giant cell arteritis (GCA) co-existent with systemic lupus erythematosus (SLE)/rheumatoid arthritis (RA) overlap syndrome
Authors: Steward Matthew , Lee Wah Phin , Ediriweera Anushka , Savanovic-Abel Ognjenka 
Published: September 2019

Abstract

Introduction
The diagnosis of GCA is relatively straightforward. However, the diagnosis of GCA can be more challenging in the context of complicated SLE and RA in part due to the rarity of the combination of autoimmune disorders. To our knowledge, it is rarely reported in the literature. This case highlights the pitfalls of diagnosis and the added complexities and difficulties in diagnosing GCA in the context of SLE/RA overlap syndrome.

Case description
We present a 74-year-old lady with SLE/RA overlap syndrome (RF/ANA & anti-Ro positive) with a medical background of lupus nephritis (WHO grade III), atrial fibrillation and hypothyroidism.
She was in clinical remission from RA/SLE whilst on hydroxychloroquine and a yearly rituximab infusion. She then re-presented with a four-week history of fronto-temporal headache progressing to scalp tenderness and pain waking her from sleep. She denied visual symptoms or jaw claudication and there were no features of active lupus or RA. Her C-reactive protein was 62. She was assessed at the rheumatology clinic one week after commencement of prednisolone (40mg) by her GP, with some improvement of symptoms and referred for temporal artery biopsy (TAB) which was negative. By then her symptom improvement with steroid was not consistent. CT head was arranged which showed features that could be related to neuro-lupus.
As a result, prednisolone was weaned off quickly. In the next few months, she suffered joint flares and constitutional symptoms despite rituximab and was started on mycophenolate. She also had visual symptoms which were contributed to cataract by the ophthalmologist. Her RA and SLE responded to mycophenolate, but her headache persisted with a further CRP rise to 100 in the absence of RA/SLE features. In this instance, ultrasound demonstrated the ‘halo effect’ in axillary artery on left. She was referred for a repeat TAB which revealed florid GCA findings histologically and was restarted on 60mg prednisolone.
During further reduction of her steroid she was re-admitted 6 months later with new neurological symptoms in keeping with an acute stroke. Her MRI head demonstrated multiple infarcts possibly related either to vasculitis or embolic source. However CT angiogram concluded atheromatous changes as opposed to vasculitic. CRP was 10. At present she remains in clinical remission with a moderately elevated CRP.

Discussion
GCA is diagnosed on the basis of clinical features, laboratory features and positive histology on TAB. Temporal headache, visual symptoms, jaw claudication characterise the GCA, and persistent severe headache can be a manifestation of cerebral lupus in patient who has the diagnosis of SLE. Therefore, in this case, the histological confirmation was essential in the diagnosis of GCA. Even though negative biopsy was discouraging at first, her persistent headache along with further rising of CRP led us to repeat biopsy on the contralateral side which was positive, confirming the diagnosis of GCA. Temporal artery biopsy could be negative an estimated 15-20% of cases, often due to length of biopsy sample, skip lesions and use of steroids pre-biopsy. There is up to a 5% chance of the contralateral biopsy being positive when the first biopsy was negative for GCA.
SLE/RA overlap syndrome is uncommon with an estimated prevalence of between 1-2% of patients with lupus and a general prevalence of around 0.09%. Patients have a tendency towards RA symptoms with typically less SLE features. This case posed diagnostic uncertainty given the persistent features of headache and variable CRP following reduction in steroid therapy, all of which could have been related to symptoms of SLE/RA rather than GCA. Persistently raised inflammatory markers in a scenario with an overlap of 3 inflammatory diseases make unpicking clinical features and an approach to management much more complex in regard to making treatment decisions. There is no data available to guide the management of GCA in these patients.

Key learning points
GCA has a heterogeneous clinical presentation which may be complicated by concurrent auto-immune disease and the features of the conditions could overlap. One negative TAB should not discourage performing repeat TAB in this instance if there is high degree of clinical suspicion. Temporal artery biopsy is commonly negative and there is a growing role for the use of ultrasound in the diagnosis of GCA, the combination of these two investigations could increase the diagnostic yield. Place of PET CT or MR angiogram in diagnosis of GCA in this context should be considered.
In the presence of persistently high CRP without clinical evidence of active flare could indicate subclinical inflammation, the approach to which is uncertain. Tocilizumab is licensed for rheumatoid arthritis and recently gained a license for treatment of giant cell arteritis; however there is no sufficient evidence on efficacy and safety in lupus although there is promising outcome from a phase one open label trial.

Conflict of interest
The authors declare no conflicts of interest.