Aspergillus is a genus of mold comprising hundreds of species, commonly found in soil, decaying vegetation, and household dust. Most individuals breathe in the microscopic spores daily without adverse effects, as a healthy immune system manages the exposure. Cutaneous aspergillosis (CA) is an uncommon infection where these fungal species invade the skin, typically signaling a disruption in the body’s natural defenses. This infection requires prompt medical attention due to its association with underlying health issues.
Conditions That Increase Susceptibility
Cutaneous aspergillosis is strongly correlated with a compromised immune system, which allows Aspergillus spores to establish an infection. Individuals undergoing intensive chemotherapy, those who have received an organ transplant, or patients with uncontrolled human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) face a heightened risk. These conditions often lead to neutropenia, a drop in infection-fighting white blood cells, which is a major factor in the fungus’s ability to invade.
The infection occurs through two distinct mechanisms: primary and secondary cutaneous aspergillosis. Primary infection results from direct inoculation, where the fungus enters through a break in the skin’s protective barrier. This entry frequently happens at sites of trauma, such as surgical wounds, burns, or around intravenous (IV) catheter insertion points. Secondary infection, which is more common, occurs when the fungus spreads to the skin through the bloodstream from a deep-seated systemic infection, usually originating in the lungs.
Recognizing the Symptoms on Skin
The appearance of cutaneous aspergillosis lesions varies widely, depending on whether the infection is primary or secondary. Primary lesions, resulting from direct entry, often begin as localized, red, and tender areas of inflammation (induration or erythema). These may progress quickly, developing into painful, raised plaques, pustules, or nodules. A hallmark of progression is the formation of a necrotic ulcer or a scab (an eschar), which appears as black, dead tissue.
In cases of primary infection associated with IV sites or occlusive dressings, the initial sign may be a hemorrhagic bulla, a large, blood-filled blister. Secondary lesions, which signal a disseminated infection, often appear as multiple, widespread macules or papules. These lesions can quickly evolve into ulcerative nodules that look similar to ecthyma gangrenosum, a condition typically caused by bacteria. The non-specific appearance of these manifestations sometimes complicates early recognition and diagnosis.
Medical Confirmation and Treatment
Confirming a diagnosis of cutaneous aspergillosis relies on specific laboratory and pathological procedures, as clinical symptoms alone are not sufficient. A skin biopsy is typically performed, where a tissue sample is taken from the lesion for histopathological examination. This tissue is stained to visualize the characteristic fungal hyphae, which are septate and show distinct 45-degree angle branching.
Fungal culture is another method, where a sample from the lesion is grown in a specialized medium to confirm the presence and species of Aspergillus. The diagnosis is definitive when both the culture is positive and the histopathology shows invasive fungal elements. Prompt intervention is necessary, especially for immunocompromised patients, to prevent the infection from spreading.
Treatment usually involves systemic antifungal medications administered intravenously or orally for an extended period. Azole antifungals, such as voriconazole or isavuconazole, are commonly used as first-line agents due to their effectiveness against Aspergillus species. Liposomal amphotericin B may be used in specific cases, particularly if there are concerns about drug resistance or interactions. Surgical debridement is also a component of therapy, involving the removal of infected and necrotic tissue to limit local fungal spread.
Reducing Environmental Exposure
For individuals with underlying health conditions, minimizing contact with Aspergillus spores is a practical strategy. High-risk activities like gardening, raking leaves, or handling compost and decaying plant matter should be avoided. Construction or excavation sites aerosolize large amounts of fungal spores, and these dusty environments should be bypassed.
If exposure to dusty conditions is unavoidable, wearing a National Institute for Occupational Safety and Health (NIOSH)-approved N95 respirator mask can help filter inhaled spores. Maintaining meticulous hygiene around any break in the skin, including surgical incisions or medical device insertion sites, is important. Healthcare providers may prescribe prophylactic antifungal medication for individuals at the highest risk, such as those undergoing stem cell transplantation.