Aspergillus is a common type of mold, a microscopic fungus, found widely in the natural environment, including soil, decaying vegetation, and even indoor air. Most people breathe in Aspergillus spores daily without any ill effects. However, under specific circumstances, this mold can affect the skin, leading to a condition known as cutaneous aspergillosis. This skin involvement is less common than other forms of aspergillosis, which typically affect the lungs or sinuses.
How Aspergillus Appears on Skin
Cutaneous aspergillosis can present in several ways. Lesions often begin as single or multiple red or violet hardened patches or bumps, which may or may not be tender. These initial manifestations can resemble common skin conditions like cellulitis.
As the infection progresses, these lesions can develop into blisters filled with pus or blood. Ultimately, these blisters may break down, forming necrotic, blackened ulcers or scabs. These skin changes most frequently appear on the limbs and head, and their size can vary from small, localized areas to larger, more widespread involvement. In some instances, particularly in newborns, the lesions might present as pustules or discharge-producing sores.
Primary cutaneous aspergillosis, where the mold directly infects the skin, often starts at a site of skin trauma, such as a wound from a blood test or an intravenous cannula insertion. These infections can initially show redness and hardening at the puncture site. Secondary cutaneous aspergillosis occurs when the infection spreads to the skin from internal organs, most commonly from the lungs, through the bloodstream.
Factors Leading to Skin Involvement
Aspergillus affects the skin when its spores enter the body through a break in the skin barrier. Common entry points include cuts, burns, surgical wounds, or sites where medical devices like intravenous catheters are inserted. Prolonged skin moisture or the use of occlusive dressings can also create an environment conducive to infection.
The development of a skin infection by Aspergillus is linked to a weakened immune system. Individuals undergoing chemotherapy, those who have received organ transplants, or people with certain medical conditions that compromise immunity are more susceptible. Long-term corticosteroid use also increases vulnerability. In healthy individuals, primary cutaneous aspergillosis is associated with significant exposure to Aspergillus spores and repeated skin injuries, such as those experienced by farmers or gardeners.
Identifying and Treating Skin Infections
Diagnosing Aspergillus skin infections involves a thorough physical examination followed by specific laboratory tests. A skin biopsy of the affected lesion is a common diagnostic step. This biopsy specimen is divided, with one part sent for fungal culture, and the other part for histopathology. Histopathology involves examining tissue under a microscope to visualize the fungal hyphae.
Treatment for cutaneous aspergillosis involves antifungal medications, which can be administered topically for superficial infections or systemically (oral or intravenous) for more severe or widespread cases. Voriconazole is a recommended first-line antifungal, with other options including itraconazole, posaconazole, or amphotericin B. The duration of antifungal therapy can last several weeks to months, depending on the severity of the infection and the patient’s immune status. Surgical removal of the infected tissue may be combined with antifungal medication to achieve a cure, particularly for localized lesions. Addressing any underlying predisposing factors, such as optimizing immune function, is also an important aspect of managing the infection.