Spectrum of Mycoses



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Spectrum of Mycoses

Thomas J. Walsh

Dennis M. Dixon

General Concepts

Classification of Mycoses

The clinical nomenclatures used for the mycoses are based on the



  1. site of the infection,

  2. route of acquisition of the pathogen, and

  3. type of virulence exhibited by the fungus.

Classification Based on Site

Mycoses are classified as

  • superficial,

  • cutaneous,

  • subcutaneous,

  • systemic (deep) infections depending on the type and degree of tissue involvement and the host response to the pathogen.

Classification Based on Route of Acquisition

Infecting fungi may be either



  • exogenous: Routes of entry for exogenous fungi include airborne, cutaneous or percutaneous

  • endogenous. Endogenous infection involves colonization by a member of the normal flora or reactivation of a previous infection.

Classification Based on Virulence

Primary pathogens can establish infections in normal hosts. Opportunistic pathogens cause disease in individuals with compromised host defense mechanisms.



Epidemiology

The primary pathogens have relatively well-defined geographic ranges; the opportunistic fungi are ubiquitous.





INTRODUCTION

Current magnitude and problems of mycoses

Fungal infections or mycoses cause a wide range of diseases in humans. Mycoses range in extent from

superficial infections involving the outer layer of the stratum corneum of the skin to disseminated infection involving the brain, heart, lungs, liver, spleen, and kidneys. The range of patients at risk for invasive fungal infections continues to expand beyond the normal host to encompass patients with the acquired immunodeficiency syndrome; those immunosuppressed due to therapy for cancer and organ transplantation, and those undergoing major surgical procedures. Each of these patient populations has a high risk of developing invasive fungal infections. As the population at risk continues to expand so also does the spectrum of opportunistic fungal pathogens infecting these patients also continue to increase. Many of the deeply invasive mycoses are difficult to diagnose early and often difficult to treat effectively. The development of new approaches to diagnosis and treatment of invasive fungal infections is the subject of intensive research.

Concepts of classification

Fungal infections may be classified according to



  1. the site of infection,

    • superficial,

    • cutaneous,

    • subcutaneous, and

    • deep

  2. route of acquisition,

  3. type of virulence

Superficial mycoses are limited to the stratum corneum and essentially elicit no inflammation.

Cutaneous infections involve the integument and its appendages, including hair and nails. Infection may involve the stratum corneum or deeper layers of the epidermis. Inflammation of the skin is elicited by the organism or its products.

Subcutaneous mycoses include a range of different infections characterized by infection of the subcutaneous tissues usually at the point of traumatic inoculation. An inflammatory response develops in the subcutaneous tissue frequently with extension into the epidermis.

Deep mycoses involve the lungs, abdominal viscera, bones and or central nervous system. The most common portals of entry are the respiratory tract, gastrointestinal tract, and blood vessels (Fig. 75-2).





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