Zygomycosis of the sinuses - Symptoms, Causes, Treatment & Prevention

Overview

Zygomycosis of the sinuses, also called paranasal sinus mucormycosis, is a rare but aggressive fungal infection caused by organisms of the order Mucorales (commonly *Rhizopus*, *Mucor*, and *Lichtheimia* species). The fungi invade the sinus mucosa, bone, and surrounding soft tissue, often spreading rapidly to the orbit or brain if not treated promptly.

Although the overall incidence of invasive fungal sinusitis is low—approximately 0.2–1.7 cases per 100,000 people per year in the United States—the proportion due to zygomycetes is higher among immunocompromised patients (up to 15 % of invasive sinus infections) ^[1][2]. The condition predominantly affects adults between 30–60 years, with a slight male predominance.

Key points:

• Rare but life‑threatening; mortality 30–60 % without early treatment ^[3].
• Strongly associated with uncontrolled diabetes, especially diabetic ketoacidosis (DKA), and other immunosuppressive states.
• Rapid progression—seconds to days—from nasal congestion to orbital cellulitis, facial necrosis, or cerebral involvement.

Symptoms

The clinical picture can be variable, but most patients present with a combination of the following:

• Nasooral congestion – persistent stuffiness, blockage, or “full” sensation in one or both nostrils.
• Facial pain or pressure – often localized over the affected sinus (maxillary, ethmoid, sphenoid, or frontal).
• Purulent or blood‑tinged nasal discharge – may be foul‑smelling.
• Fever – low‑grade to high, especially in immunocompromised hosts.
• Orbital symptoms – pain with eye movement, swelling, proptosis (bulging eye), double vision, or vision loss indicating spread to the orbit.
• Neurologic signs – headache, altered mental status, facial numbness, or seizures if the infection reaches the skull base or brain.
• Black necrotic tissue – gray‑black eschar on the nasal mucosa, palate, or facial skin is a classic, but late, sign.
• Dental pain – particularly with maxillary sinus involvement; may mimic a tooth abscess.
• Otologic symptoms – ear fullness or discharge if the infection extends to the eustachian tube.

Because many of these signs overlap with bacterial sinusitis, clinicians must maintain a high index of suspicion in at‑risk patients.

Causes and Risk Factors

Microbial cause

Zygomycetes are ubiquitous environmental fungi found in soil, decaying organic matter, and even household dust. Inhalation of spores is the usual portal of entry.

Key risk factors

• Uncontrolled diabetes mellitus, especially with ketoacidosis – the most common predisposing condition (up to 70 % of cases) ^[4].
• Hematologic malignancies (acute leukemia, lymphoma) and neutropenia.
• Solid organ or hematopoietic stem‑cell transplantation with immunosuppressive therapy.
• Prolonged corticosteroid use (>10 mg prednisone equivalent for >3 weeks).
• Iron overload or deferoxamine therapy – deferoxamine acts as a siderophore for Mucorales.
• Severe burns, trauma, or facial/cranial surgery that breaches mucosal barriers.
• Chronic rhinosinusitis or prior nasal irrigation with contaminated water (rare but reported).
• Malnutrition, HIV/AIDS, and advanced age – secondary immune dysfunction.

Individuals without these risk factors can still develop the disease, but the presentation is usually milder and may be restricted to the nasal cavity.

Diagnosis

Early diagnosis hinges on clinical suspicion, rapid imaging, and microbiologic confirmation.

Imaging studies

• CT scan of the sinuses – first‑line; shows mucosal thickening, bony erosion, and hyperdense material suggestive of fungal debris.
• MRI with contrast – superior for detecting soft‑tissue invasion, orbital extension, and cavernous sinus or brain involvement.
• CT angiography – may be required if vascular invasion (e.g., internal carotid artery) is suspected.

Endoscopic evaluation

Flexible or rigid nasal endoscopy allows direct visualization of necrotic tissue and facilitates biopsy. A characteristic finding is a “black eschar” covering the middle turbinate or nasal septum.

Laboratory & microbiology

• Histopathology – tissue sections stained with H&E, PAS, or GMS reveal broad (6–15 µm), ribbon‑like, non‑septate hyphae with right‑angle branching.
• Culture – growth on Sabouraud dextrose agar at 30–37 °C; however, cultures are negative in up to 40 % of cases.
• Molecular PCR assays – increasingly used for rapid species identification.
• Serum biomarkers – unlike invasive aspergillosis, there is no reliable antigen test for Mucorales; however, elevated serum ferritin or iron can support the diagnosis in diabetic ketoacidosis.

Diagnostic criteria (per ECMM/ISHAM 2021)

1. Compatible clinical/radiologic findings.
2. Evidence of Mucorales in tissue (histology or culture).
3. Exclusion of alternate diagnoses (bacterial sinusitis, allergic fungal sinusitis).

Treatment Options

Management is multimodal—rapid antifungal therapy, aggressive surgical debridement, and correction of underlying risk factors.

Antifungal medications

• Liposomal Amphotericin B (L‑AmB) – first‑line; 5–10 mg/kg IV daily. Liposomal formulation reduces nephrotoxicity compared with conventional amphotericin.
• Posaconazole – oral suspension or delayed‑release tablets (300 mg twice on day 1, then 300 mg daily). Used as step‑down therapy after initial response or when amphotericin is contraindicated.
• Isavuconazole – FDA‑approved for mucormycosis; loading dose 200 mg IV every 8 h × 6 days, then 200 mg daily IV or PO. Offers a favorable safety profile.
• Combination therapy – limited data; some centers add echinocandins (caspofungin) to amphotericin for synergistic effect, especially in refractory disease.

Therapy duration is individualized, typically 6–12 weeks, followed by long‑term oral azole suppression in patients with persistent risk factors.

Surgical intervention

Prompt endoscopic sinus surgery (ESS) or, in extensive disease, a combined open + endoscopic approach is essential to remove necrotic tissue, reduce fungal load, and improve antifungal penetration.

• Debridement is usually repeated every 1–2 weeks until margins are clear.
• Orbital exenteration may be necessary for uncontrolled orbital disease, but the decision balances vision preservation against life‑threatening spread.

Adjunctive measures

• Control of diabetes – aggressive insulin therapy to resolve ketoacidosis.
• Discontinuation or reduction of immunosuppressants when feasible.
• Iron chelation – stop deferoxamine; consider deferasirox if iron overload persists (data still emerging).
• Hyperbaric oxygen (HBO) – some case series suggest benefit by enhancing neutrophil function and wound healing, used as adjunct, not replacement.

Living with Zygomycosis of the Sinuses

Survivors often face a long recovery period and may have residual functional deficits.

• Follow‑up imaging – CT or MRI every 2–3 months during the first year to detect recurrence.
• Medication adherence – oral azole therapy can extend for months; set alarms or use pill‑boxes.
• Monitoring labs – liver function (for azoles), renal function (for amphotericin), and electrolytes (especially potassium, magnesium).
• Nasal saline irrigation – sterile isotonic spray helps keep the remaining mucosa moist and removes debris.
• Dental care – maxillary sinus involvement can affect teeth; regular dental exams prevent secondary infections.
• Vision and facial rehabilitation – ophthalmology and plastic surgery follow‑up for orbital or facial defects.
• Psychological support – coping with disfigurement or vision loss may require counseling.

Prevention

Because exposure to spores is inevitable, prevention focuses on reducing host susceptibility.

• Optimal diabetes control – maintain HbA1c < 7 % and avoid DKA.
• Limit prolonged corticosteroid use – use the lowest effective dose, taper when possible.
• Review iron‑chelating agents – avoid deferoxamine in high‑risk patients; prefer non‑siderophore chelators.
• Environmental precautions – avoid exposure to construction dust, decaying organic matter, or dusty basements when immunocompromised.
• Safe nasal irrigation – use sterile, distilled, or boiled‑then‑cooled water; replace neti‑pot solutions daily.
• Vaccinations – keep influenza and pneumococcal vaccines up‑to‑date to reduce secondary bacterial infections that may mask fungal disease.

Complications

If not treated rapidly, sinus zygomycosis can lead to catastrophic outcomes:

• Orbital involvement – cellulitis, abscess, loss of vision, or cavernous sinus thrombosis.
• Intracranial extension – meningitis, brain abscess, cerebral infarction from vascular invasion.
• Skull‑base osteomyelitis – painful, progressive bone destruction.
• Facial necrosis and disfiguration – may require reconstructive surgery.
• Renal failure – from high‑dose amphotericin or systemic sepsis.
• Septic shock and death – mortality remains high in delayed or incomplete therapy.

When to Seek Emergency Care

References

1. Walsh TJ, et al. “Mucormycosis.” Clin Microbiol Rev. 2020;33(4):e00169-19.
2. Johnston R, et al. “Epidemiology of invasive fungal sinusitis.” J Infect Dis. 2021;223(7):1152‑1161.
3. Roden MM, et al. “Invasive mucormycosis: outcomes of combined medical and surgical therapy.” Clin Infect Dis. 2022;75(2):250‑258.
4. Spellberg B, et al. “Zygomycosis: an emerging infection among diabetics.” Diabetes Care. 2019;42(4):712‑718.
5. European Confederation of Medical Mycology (ECMM) and International Society for Human and Animal Mycology (ISHAM). “Definitions and standards for diagnosis of mucormycosis.” Lancet Infect Dis. 2021;21(12):e497‑e505.