Some fungi can only infect the skin when it is damaged. Intact, undamaged skin is a very effective defense against these kinds of fungi. The respiratory tract also has defenses which it uses against fungi that can cause infection when people inhale their spores. However, these defenses of the respiratory system are suppressed when the immune system is impaired due to illness, age, or certain medications or medical conditions.
Trichophyton
Trichophyton is a species of fungus that infects the nails, skin and hair. All of the fungi in this species can cause more infections when their environment is warm and moist. The most common one in this group is Tinea pedis, writes George Brooks, M.D., in "Jawetz, Melnick, & Adelberg's Medical Microbiology." Tinea pedis causes athlete's foot, which begins with an itch between the toes and can develop into cracking and peeling skin. Tinea corporis infects the palms and soles, while Tinea cruris is also called "jock itch."
Mucor, Rhizopus, Absidia
These fungi are usually grouped together because they cause a disease called mucormycosis. The disease primarily affects people who are not controlling their diabetes, those with an impaired immune system and those taking a medication named deferoxamine, according to The Merck Manuals Online Medical Library. After inhaling the spores of any one of these fungi, the fungus will usually invade the mucous membrane in the nose, then the sinuses, the bones around the eyes and sinuses, and the brain.
Aspergillus
This kind of fungus can cause infection in people who have an impaired immune system. Some people may develop allergic bronchopulmonary aspergillosis, a lung infection where they wheeze as if they have allergies or asthma. Other people may develop a "fungus ball." This is a mass of tangled aspergillus fungi and tissue. Sometimes the fungus invades the blood vessels and causes hemorrhaging or even invades the brain. Aspergillus is also the number one cause of fungal sinusitis, or the inflammation of the sinuses because of a fungal infection, notes the "Review of Medical Microbiology and Immunology."
Cryptococcus Neoformans
Cryptococcus neoformans causes lung infections that usually heal on their own without any medication except for people who have a weakened immune system. For them, this kind of fungus can spread throughout the body. Anyone who has AIDS and develops a cryptococcal infection needs treatment the rest of their life. The Merck Manuals Online Medical Library notes that this fungus especially infects the meninges, or the membrane that covers the brain. The infection causes meningitis, or the inflammation of the meninges, and it is a life-threatening infection.
References
- "Jawetz, Melnick, & Adelberg's Medical Microbiology"; George Brooks, M.D., Karen Carroll, M.D., Janet Butel, Ph.D., Stephen Morse, Ph.D.; 2007
- "Review of Medical Microbiology and Immunology"; Warren Levinson, M.D., Ph.D.; 2008
- The Merck Manuals Online Medical Library: Mucormycosis
