| Zygomycosis | |
|---|---|
 | |
| Group of periorbital fungal infections includingmucormycosis (shown) andphycomycosis | |
| Specialty | Infectious diseases  |
Zygomycosis is the broadest term to refer to infections caused bybread moldfungi of thezygomycota phylum. However, because zygomycota has been identified aspolyphyletic, and is not included in modern fungal classification systems, the diseases that zygomycosis can refer to are better called by their specific names:mucormycosis[1] (afterMucorales),phycomycosis[2] (afterPhycomycetes) andbasidiobolomycosis (afterBasidiobolus).[3] These rare yet serious and potentially life-threatening fungal infections usually affect theface ororopharyngeal (nose and mouth) cavity.[4] Zygomycosis type infections are most often caused by common fungi found in soil and decaying vegetation. While most individuals are exposed to the fungi on a regular basis, those with immune disorders (immunocompromised) are more prone to fungal infection.[2][5][6] These types of infections are also common after natural disasters, such as tornadoes or earthquakes, where people have open wounds that have become filled with soil or vegetative matter.[7]
The condition may affect thegastrointestinal tract or theskin, often beginning in the nose and paranasalsinuses. It is one of the most rapidly spreading fungal infections in humans. Treatment consists of prompt and intensiveantifungal drug therapy andsurgery to remove the infected tissue.
In the primary cutaneous form, the lesions are usually painful and necrotic, with blackeschar, accompanied by a fever. Patients will usually present with a history of poorly controlled diabetes or malignancy.[8] Myocutaneous infections may lead to amputation. Pulmonary tract infections seen with lung transplant patients, who are at high risk for fatal invasive mycoses.[9] Rhinocerebral infection is characterized by paranasal swelling with necrotic tissues. Patient may have hemorrhagic exudates (tissue fluid from lesions tinged with blood) from the nose and eyes as the fungi penetrate through blood vessels and other anatomical structures.[10]
Pathogenic zygomycosis is caused by species in two orders:Mucorales orEntomophthorales, with the former causing far more disease than the latter.[11] These diseases are known as "mucormycosis" and "entomophthoramycosis", respectively.[12]
Diagnosis is done withpotassium hydroxide (KOH) preparation in tissue. On light microscopy, there will be broad, ribbon-likeseptate hyphae with 90 degree angles on branches.[10] KOH wet mount of the black eschar will show fungalaseptate hyphae with right angle branching.Periodic Acid Schiff (PAS) staining will reveal similar broad hyphae in the dermis and cutis. Fungal culture can also confirm the organism.[13] Diagnosis remains difficult due to the lack of laboratory tests as mortality remains high. In 2005, a multiplex PCR test was able to identify five species ofRhizopus and may prove useful as a screening method for visceral mucormycosis in the future.[14]
The clinical approach to diagnosis includes radiologic, where more than ten nodules and pleural effusion are associated to pulmonary forms of the disease. In CT, a reverse halo sign is noted. Direct microscopy and histopathology, and cultures remain the gold standards for diagnoses.[15]Zygomycophyta share close clinical and radiological features to Aspergillosis. Invasive procedures such as bronchial endoscopy and lung biopsy may be necessary to confirm pulmonary diagnosis are no validated indirect tests are available. Quantitative polymerase chain reaction to detect serum DNA of the pathogen shows promise.[16]
The condition may affect thegastrointestinal tract or theskin. In non-trauma cases, it usually begins in the nose and paranasalsinuses and is one of the most rapidly spreading fungal infections in humans.[2] Common symptoms includethrombosis and tissuenecrosis.[17]
Due to the organisms' rapid growth and invasion, zygomycosis presents with a high fatality rate. Treatment must begin immediately with debridement of the necrotic tissue plusamphotericin B.[10] Complete excision of the infectious tissue may be required as suspected dead tissue must be excised aggressively.[13][18][19] In a documented case, conservative surgical drainage and intravenous amphotericin B in an insulin-dependent diabetic was proven effective in sino-orbital infection.[20] The prognosis varies vastly depending upon an individual patient's circumstances.[17]
Zygomycosis has been found in survivors of the2004 Indian Ocean earthquake and tsunami and in survivors of the2011 Joplin, Missouri tornado.[21]
The termoomycosis is used to describeoomycete infections.[22] These are more common in animals, notablydogs andhorses. These areheterokonts, not true fungi. Types includepythiosis (caused byPythium insidiosum) andlagenidiosis.
Zygomycosis has been described in acat, where fungal infection of thetracheobronchus led to respiratory disease requiringeuthanasia.[23]