LVV is a term used to describe a range of idiopathic chronic primary vasculitides characterised by granulomatous inflammation affecting the aorta and its major branches.
The major variants are giant cell arteritis (GCA) and Takayasu arteritis (TA).
GCA usually affects persons over the age of 50,
with a higher incidence reported in Northern European women at a ratio of 2.5:1..
TA is a rare disease usually found in young females.
It is being increasingly recognised in Europe with reported incidence estimates varying from 0.4 to 1.5 per million in recent epidemiological studies .
Diagnosis may be difficult as patients commonly present with several non-specific constitutional symptoms such as:
· loss of appetite
· fever of unknown origin
· weight loss
No approved diagnostic criteria exist for GCA and The American College of Rheumatology (ACR) criteria mainly focus on patients with cranial symptoms.
Presentation can be atypical and symptoms often do not meet criteria for ACR diagnosis [3,4].
The combination of symptoms,
histology and angiography is used to establish a diagnosis.
Inflammatory markers play an important role in diagnosis,
however they lack specificity and may not correlate to disease activity .
Temporal artery biopsy is the gold-standard test used in the diagnosis of GCA.
Although high in specificity,
this procedure remains invasive and is associated with high false-negative rates with normal results in up to 19 % of cases [6,7].
In extracranial GCA,
temporal arteries are spared in up to 40% of patients and in these circumstances,
a histological diagnosis cannot be made unless the patient undergoes open surgery to treat an established aneurysm .
Conventional angiography is useful in the diagnosis of TA however it detects late disease,
when anatomical changes such as arterial occlusions and stenoses have already occurred.
this technique is invasive and associated with several procedural complications such as vessel wall damage and iatrogenic embolism.
The limitations of the diagnostic tests described highlight the need for a non-invasive,
sensitive and specific modality to diagnose disease its early stages prior to development of complications.
functional and metabolic alterations often precede morphological change in the vessel walls.
GCA is characterised by injury to the arterial tunica intima and media,
with associated transmural infiltration of inflammatory cells.
TA is characterised by mononuclear infiltrates in giant cells involving the arterial tunica adventia and media .
These changes result in increased metabolic demands within the aggregated leucocytes and macrophages at the site of inflammatory change,
thus enabling the use of PET.
PET is a non-invasive,
metabolic imaging modality.
Although traditionally associated with cancer staging and evaluation of treatment response,
it is now assuming an increasingly important role in the diagnosis of inflammatory conditions such as LVV,
where inflammatory changes can be identified at an early stage.
Emergent studies demonstrate a good,
overall diagnostic accuracy in the use of PET for the diagnosis of LVV and changes the medical management in a significant proportion of patients [10,11].