Opportunistic Mycoses vs. Systemic

What's the Difference?

Opportunistic mycoses and systemic mycoses are two types of fungal infections that affect humans. Opportunistic mycoses occur when a person's immune system is compromised, allowing normally harmless fungi to cause infection. These infections typically affect specific areas of the body, such as the skin, nails, or mucous membranes. On the other hand, systemic mycoses are caused by fungi that are capable of infecting healthy individuals and spreading throughout the body. These infections can be more severe and affect multiple organs, including the lungs, brain, and bloodstream. While opportunistic mycoses primarily target individuals with weakened immune systems, systemic mycoses can affect anyone, although they are more common in individuals with underlying health conditions.


AttributeOpportunistic MycosesSystemic
DefinitionCaused by fungi that normally do not cause disease in healthy individualsCaused by fungi that can infect both healthy and immunocompromised individuals
Host SusceptibilityPrimarily affects immunocompromised individualsAffects both immunocompromised and immunocompetent individuals
Common PathogensCandida, Aspergillus, CryptococcusHistoplasma, Blastomyces, Coccidioides
Mode of TransmissionUsually acquired through inhalation or direct contact with contaminated materialsPrimarily acquired through inhalation of fungal spores
Organ InvolvementCan affect various organs, including lungs, skin, and mucous membranesPrimarily affects the respiratory system, but can also involve other organs
TreatmentTreated with antifungal medications, often in combination with immune system supportTreatment involves antifungal medications, sometimes requiring long-term therapy

Further Detail


Mycoses, or fungal infections, can be classified into various types based on their clinical presentation and the host's immune status. Two significant categories of mycoses are opportunistic mycoses and systemic mycoses. While both types involve fungal infections, they differ in terms of the causative agents, risk factors, clinical manifestations, and treatment approaches.

Opportunistic Mycoses

Opportunistic mycoses are fungal infections caused by organisms that are typically harmless in healthy individuals but can cause disease in immunocompromised individuals. These infections occur when the immune system is weakened, allowing the fungi to invade and multiply. Common opportunistic fungi include Candida species, Aspergillus species, Cryptococcus neoformans, and Pneumocystis jirovecii.

Opportunistic mycoses often affect individuals with conditions such as HIV/AIDS, organ transplantation, cancer, or those receiving immunosuppressive therapy. The fungi can enter the body through inhalation, ingestion, or direct contact with the skin. Once inside, they can cause localized or disseminated infections, affecting various organs and systems.

Clinical manifestations of opportunistic mycoses can vary depending on the site of infection. For example, Candida species can cause oral thrush, esophagitis, or invasive candidiasis. Aspergillus species can lead to invasive pulmonary aspergillosis, sinusitis, or disseminated disease. Cryptococcus neoformans primarily affects the central nervous system, causing meningitis. Pneumocystis jirovecii is associated with severe pneumonia in immunocompromised individuals.

Treatment of opportunistic mycoses involves antifungal medications, such as azoles, echinocandins, or polyenes, depending on the specific fungal species and the severity of the infection. In addition to antifungal therapy, managing the underlying immunosuppression or immune deficiency is crucial to prevent recurrent infections.

Systemic Mycoses

Systemic mycoses are fungal infections caused by fungi that are capable of causing disease in both immunocompromised and immunocompetent individuals. These fungi are typically found in the environment and can be inhaled or acquired through direct contact with contaminated materials. Examples of systemic fungi include Histoplasma capsulatum, Coccidioides immitis, Blastomyces dermatitidis, and Paracoccidioides brasiliensis.

Unlike opportunistic mycoses, systemic mycoses can affect healthy individuals, although the severity of the infection may vary depending on the immune status. The primary route of infection is inhalation of fungal spores, which can lead to respiratory symptoms and subsequent dissemination to other organs.

Clinical manifestations of systemic mycoses depend on the specific fungal species and the organs involved. For instance, Histoplasma capsulatum can cause flu-like symptoms, pneumonia, or disseminated disease affecting the liver, spleen, and bone marrow. Coccidioides immitis is associated with pulmonary symptoms, skin lesions, or disseminated disease involving the bones, joints, or meninges.

Treatment of systemic mycoses often requires prolonged antifungal therapy, such as azoles or amphotericin B, depending on the severity and extent of the infection. In some cases, surgical intervention may be necessary to remove infected tissues or abscesses. Early diagnosis and prompt treatment are crucial to prevent complications and improve outcomes.


Opportunistic mycoses and systemic mycoses are two distinct categories of fungal infections, differing in terms of the causative agents, risk factors, clinical manifestations, and treatment approaches. Opportunistic mycoses primarily affect immunocompromised individuals, caused by fungi that are normally harmless. In contrast, systemic mycoses can affect both immunocompromised and immunocompetent individuals, caused by fungi present in the environment. Understanding the differences between these two types of mycoses is essential for accurate diagnosis, appropriate treatment, and prevention of complications.

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