Rare diseases

Maintain a high index of clinical suspicion for AAV in patients with SSc: experts 

The combined pathologies of systemic sclerosis (SSc) and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) can result in “potentially devastating” outcomes, according to experts. Though relatively rare, they recommend a vigorous focus on definition and therapeutic strategy for SSc-AAV.

AAVs – including granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis – are characterised by small vessel inflammation, and development of antibodies toward myeloperoxidase (MPO) and proteinase 3.

“There are multiple areas of potential interaction in the pathogenesis of SSc and AAV that can exacerbate/compound underlying SSc-vasculopathy,” wrote study authors led by Dr Michael Hughes, of Sheffield Teaching Hospitals NHS Foundation Trust, in Rheumatology.

ANCA positivity is relatively common among patients with SSc, with rates as high as 35% reported in at least one study. The development of systemic vasculitis, however, is relatively rare. In one study of 2,200 patients, 1.6% had evidence of vasculitis.

“SSc-AAV can result in a devastating clinical phenotype,” the authors wrote. Kidney involvement is seen in 75 to 80% of patients, while pulmonary haemorrhage is seen in about one-third of SSc-AAV patients. Interstitial lung disease has been reported in up to 80% of patients, though the authors note the connection remains controversial.

About 10% of SSc-AAV patients develop necrotising vasculitis, resulting in limb ischaemia and vasculitic skin rash. One study reported neurological involvement in 15.7% of patients in a case series.

“The key to diagnosis is to maintain a high index of clinical suspicion as to the potential development of AAV in patients with SSc,” the authors advised. “In patients with acute renal failure and features not in keeping (or less frequently observed) with scleroderma renal crisis [SRC] and/or pulmonary haemorrhage, AAV should be strongly suspected.”

It is critical to distinguish between SRC and SSc-AAV, as the management differs significantly.

“There are no specific data to inform the treatment of SSc-AAV and therefore management invariably follows that of isolated AAV,” they wrote. “The treatment of AAV may be extremely hazardous in patients with SSc, for example, the strong association between high-dose steroid treatment and SRC.”

They call for more research to understand the complicated clinical entity, including aetiopathogenesis, and to define a therapeutic strategy for SSc-AAV.

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