Differentials
Aspergillosis
SIGNS / SYMPTOMS
No differentiating signs or symptoms. Air crescent sign upon CT chest may be more commonly seen in aspergillosis.[42] Presence of accompanying sinus disease makes aspergillosis less likely.
INVESTIGATIONS
Histopathology in aspergillosis demonstrates narrow (2.5-4.5 micrometres) septate hyphae, branching at an acute angle of 45°.
Positive serum galactomannan assay may favour the diagnosis of aspergillosis.
Bacterial sinusitis
SIGNS / SYMPTOMS
Clinically indistinguishable from mucormycosis in the initial stages, but typically responds to antibacterial therapy and lacks necrotic eschar.
INVESTIGATIONS
Sinus puncture with culture may be indicated when standard antibiotics have failed; however, this is considered controversial.
Bacterial peri-orbital cellulitis
SIGNS / SYMPTOMS
No differentiating signs and symptoms in the initial stages but more commonly lacks risk factors, has history of trauma, and responds to antibacterial therapy.
INVESTIGATIONS
Blood/eye swab cultures: positive for bacterial culture.
Sinus lymphomas
SIGNS / SYMPTOMS
B-cell or T-cell lymphomas may have presence of lymphadenopathy elsewhere in the body.
INVESTIGATIONS
Histopathology of biopsy is crucial and demonstrates atypical cells consistent with lymphoma.
Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis)
SIGNS / SYMPTOMS
May have renal failure and systemic manifestations of vasculitis in addition to sinus symptoms similar to mucormycosis.
INVESTIGATIONS
Blood test: positive anti-neutrophil cytoplasmic antibodies (ANCA) may help in diagnosis of granulomatosis with polyangiitis, but a negative ANCA test does not rule it out. In addition, granulomatosis with polyangiitis and mucormycosis can co-exist, especially in a patient treated with immunosuppressants for granulomatosis with polyangiitis.
Bacterial brain abscess
SIGNS / SYMPTOMS
No differentiating signs and symptoms.
INVESTIGATIONS
Aspiration and culture of abscess fluid is positive for bacteria.
Ecthyma gangrenosum
SIGNS / SYMPTOMS
Necrotic-appearing lesions on the skin, sometimes with surrounding erythema, occurring typically in the presence of pseudomonal sepsis. Similar host populations are vulnerable.
INVESTIGATIONS
Culture of lesions is positive for bacteria.
Fusariosis
SIGNS / SYMPTOMS
Patients with fusariosis have a high incidence of skin lesions as a manifestation of disseminated disease in >50% to 60%, as opposed to <5% to 10% in mucormycosis.[53]
Lesions are clinically indistinguishable from mucormycosis.
INVESTIGATIONS
High incidence of positive blood cultures (>50% of patients) as opposed to rare positive blood cultures in mucormycosis (<5%).[53]
Coronavirus disease 2019 (COVID-19)
SIGNS / SYMPTOMS
Consider the current COVID-19 epidemiological situation and any recent outbreaks. May give history of COVID-19 exposure or unwell contacts.
Fever, cough, and dyspnoea may mimic pulmonary mucormycosis. Patients with COVID-19 may report altered sense of smell or taste.
INVESTIGATIONS
Real-time reverse transcription polymerase chain reaction (RT-PCR): positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Rapid antigen tests may also be used.
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