Fungal Infections
Fungal infections (mycoses) are diseases caused by pathogenic fungi — yeasts, moulds, and dermatophytes — that range from common superficial infections of skin, hair, and nails to life-threatening invasive disease of deep tissues and the bloodstream. Their clinical importance has grown with the expansion of populations whose immune defences are weakened by disease or medical treatment.
Definition
A fungal infection is a disease caused by colonisation and invasion of host tissue by a fungal organism, classified by the depth and site of infection (superficial, cutaneous, subcutaneous, or deep/systemic) and by the host's immune status.
Scope
This area orients the reader to the major categories of human fungal disease and how they are grouped: invasive infections of deep organs, opportunistic infections in immunocompromised hosts, superficial dermatophyte infections of keratinised tissue, and candidiasis as a clinically dominant example. It is a navigational overview within infectious diseases, not a diagnostic or treatment guide.
Sub-topics
Key concepts
- Superficial versus deep (invasive) mycoses
- Opportunistic versus primary pathogens
- Host immune status as a determinant of disease
- Yeasts, moulds, and dermatophytes
- Antifungal drug classes and resistance
- Endemic versus ubiquitous fungi
Mechanisms
Fungi cause disease along a spectrum determined jointly by fungal virulence and host defence. Superficial mycoses are largely confined to keratinised tissue, whereas invasive disease follows breaches of barrier defences and impaired immunity. Many medically important fungi are opportunists that cause serious disease chiefly when neutrophil number or function, cell-mediated immunity, or mucosal integrity is compromised. The principal antifungal drug classes act on distinct fungal targets, and resistance to them is an increasing concern across species.
Clinical relevance
Fungal disease is a substantial and under-recognised contributor to global morbidity and mortality, and recognising the host factors that predispose to it is part of general clinical reasoning in infectious diseases. This entry describes how mycoses are categorised and studied; it is reference material and not a basis for individual diagnosis or therapy.
Epidemiology
Estimates of the global burden of serious fungal disease run into the hundreds of millions of cases annually when superficial infections are included, with several million life-threatening invasive infections and high attributable mortality. The burden of invasive disease has risen alongside growth in immunocompromised populations, and antifungal resistance compounds the problem in several settings.
History
Medical mycology emerged as a distinct discipline in the nineteenth and twentieth centuries, with dermatophytes among the first human pathogens to be linked microscopically to disease. The latter twentieth century saw invasive and opportunistic mycoses move to the foreground as transplantation, cancer chemotherapy, critical care, and HIV expanded the population at risk.
Related topics
Seminal works
- bongomin-2017
- perlin-2017
Frequently asked questions
- How are fungal infections classified?
- They are commonly grouped by the depth and site of infection — superficial, cutaneous, subcutaneous, and deep or systemic — and by whether they occur in otherwise healthy hosts or chiefly as opportunists in people with impaired immunity.
- Why have invasive fungal infections become more common?
- Their rise tracks the growth of populations with weakened immune defences, including transplant recipients, patients receiving cancer chemotherapy, critically ill patients, and people with advanced HIV.