Mucormycosis cerebral arteritis mimicking a flare in ANCA-associated vasculitis

Abstract

A 65-year-old man presented with type 2 diabetes and a relapsing antineutrophil cytoplasmic antibody (ANCA)associated vasculitis. He was admitted for a suspected new vasculitis fl are with the onset of frontal headache. Brain CT and MRI showed sinusitis and right hemispherical recent ischaemic lesions. The patient developed left hemiplegia and died. Autopsy showed multiple areas of right hemispherical brain infarctions and a segmental destruction of the right middle cerebral artery wall by an abscess with the presence of many hyphae in the media and many mycotic thrombi occluding the wall (fi gure, A–D; hemalum-phloxine staining in A, Weigert staining in B, and Gomori-Grocott staining in C). Mucormycosis is becoming increasingly common in immunocompromised patients. Patients with diabetes are especially vulnerable. Rhinocerebral mucormycosis is the most common form of the infection. The clinical hallmark is vascular invasion, but mycotic arteritis is rarely documented. The neurological signs of our patient could be explained by a parietal involvement of the right middle cerebral artery with wall segmental destruction by an abscess (fi gure, A–C) leading to cerebral ischaemia in the zone of vascularisation. The multiple areas of right hemispherical infarctions could have also resulted from previous septic fungi emboli. A high index of suspicion is required to make the diagnosis of rhinocerebral mucormycosis, as evidenced by the fact that half of all cases are diagnosed post mortem, as was the case for our patient. Diagnosis relies on identifi cation of the fungal agent either by culture or histology. Nevertheless, culturing organisms from a potentially infected tissue is rarely suffi cient to establish diagnosis because the causative agent is ubiquitous and a relatively frequent laboratory contaminant. Furthermore, the organism can be killed as tissue specimens are processed for culture, and it is rarely isolated from samples of infected areas. Biopsies of sinus mucosa, thickened extraocular muscles, or both are thus warranted. Direct microscopic examination should show the characteristic wide, ribbon-like, aseptae hyphal elements that branch at right angles (fi gure, D). Delayed diagnosis has been associated with poor outcomes. Survival depends on the clinical form of the infection, the nature of underlying disease, and the prompt initiation of treatment. In conclusion, mucormycosis can mimic a vasculitis fl are in patients with underlying vasculitis. A high degree of awareness is warranted to rule out mucormycosis in immunocompromised patients with systemic disease before a cerebral disease fl are is conclusively diagnosed.