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DIAGNOSIS THROUGH CLINICAL FEATURES, PATHOLOGY AND LABORATORY EXAMINATIONS
Giant cell arteritis is a systemic idiopathic vasculitis with a few very unusual features: it affects the large- and medium-calibre arteries of subjects who are only ever over the age of 60. The lesions predominate in the network of vasculature around the external carotid artery and they cause a number of ischaemic phenomena in the face.
This diagnosis must be considered in a subject with disease-specific (50 – 70%) (clinical abnormality of the temporal arteries, jaw claudication, facial necrosis) or non-specific signs (headaches, scalp hyperesthesia) presenting in the head. The ophthalmological signs (10 - 30%) render this disease very serious in the immediate term but they are not pathognomonic (reduced visual acuity, oculomotor nerve palsy, ptosis, pupil abnormalities); blindness due to acute anterior optic nerve ischaemia may be revealed by transient signs (amaurosis fugax) and as a rule this is irreversible once established. Signs affecting the head may also be lacking and the disease must be still considered in the presence of less suspicious signs, whether they are general (50%) (deterioration in general health, fever), vascular (limb claudication, inflammatory aneurysms, especially aortic aneurysms, and even some forms of stroke, or myocardial or intestinal ischaemia), rheumatological (50%) (polymyalgia rheumatica, RS3PE), or respiratory (5 – 10%) (unexplained dry cough).
Dermatological signs are rare in giant cell arteritis. Necroses of the face (scalp, tongue, lips) are exceptional but highly suspicious; they point to diffuse disease and/or disease that has been aggravated by use of a vasoconstrictor (for example, an anti-migraine treatment initiated in error for headaches). Involvement of the large vessels sometimes manifests as Raynaud’s syndrome. Cutaneous vasculitis is almost never part of giant cell arteritis, or when it is, in exceptional cases, it exists as a borderline form with other types of systemic vasculitis.
Since the clinical signs are often not particularly suspicious, it is often signs of very significant inflammation (95% of cases) that draw the clinician’s attention, and these are ideally measured by acute phase proteins, because the erythrocyte sedimentation rate is sometimes difficult to interpret in older subjects. There is no other laboratory examination that has demonstrated any value in the diagnosis of giant cell arteritis.
Imaging is of minimal value in diagnosing this disease. Some examinations may be useful, particularly to exclude other causes of unexplained headaches or inflammation in an elderly patient. Colour-Doppler sonography of the temporal arteries is promising when it shows flow abnormalities associated with a halo sign surrounding the artery, but it remains for the use of trained teams with the appropriate equipment.
Once it has been suggested, the diagnosis must be confirmed by pathological examination of an arterial specimen, usually from the superficial temporal artery or one of its branches. The examination will ideally use an arterial specimen of at least 3 cm in size that is established as pathological on clinical assessment or sonography. The presence of an inflammatory infiltrate of mononuclear cells within the arterial wall generally points to this diagnosis, since the typical finding of granuloma in the tunica media centred on the internal elastic lamina fragmented by giant mononuclear cells is not always present. If the arterial specimen is short, because of the segmental nature of these lesions, this means that the temporal artery biopsy could be negative (around 30% of cases in Europe). Corticosteroid therapy for a period of few days to a few weeks does not mask the histological signs of the disease. In fewer than 2% of cases, the temporal artery biopsy will lead to diagnosis of a different form of systemic vasculitis, but the confirmed diagnosis of this will depend on associated clinical and pathological signs and laboratory examinations.
There are two main points that it is important for patients to understand. Firstly, the initial risk of blindness justifies the swiftness with which they are prescribed steroids, sometimes even before the diagnosis has been confirmed. In the longer term, the essential requirements of the diet and additional steps to follow while taking corticosteroids must often be re-explained in order to avoid facial lipodystrophy and other complications.
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