Dermatophytic and Subcutaneous Mycoses: Understanding Cutaneous Fungal Infections and Their Subdermal Affect

Dermatophytic and Subcutaneous Mycoses: Understanding Cutaneous Fungal Infections and Their Subdermal Affect

 

INTRODUCTION

Medical mycoses could be divided into 4 classes: (1) cuta-

neous, (2) subcutaneous, (3) systemic, and (4) opportunistic.

Some options of the vital fungal ailments are described

in Desk 48–1. Cutaneous and subcutaneous mycoses are dis-

stubborn on this chapter, and vital options of the causative

organisms are described in Desk 48–2. The systemic and

opportunistic mycoses are mentioned in Chapters 49 and 50,

respectively.

CUTANEOUS MYCOSES

Dermatophytoses

Dermatophytoses are attributable to fungi (dermatophytes) that

infect solely superficial keratinized buildings (pores and skin, hair, and

nails), not deeper tissues. A very powerful dermatophytes

are categorised in to a few genera: Trichophyton, Epidermophyton,

and Microsporum. They’re unfold from contaminated individuals by

direct contact. Microsporum can be unfold from animals such

as canines and cats. This means that to forestall reinfection, the

animal have to be handled additionally.

Dermatophytoses (tinea, ringworm) are persistent infec-

tions typically situated within the heat, humid areas of the physique

(e.g., athlete’s foot and jock itch).1

Typical ringworm lesions

have an infected round border containing papules and ves-

icles surrounding a transparent space of comparatively regular pores and skin. The

lesions are usually pruritic. Damaged hairs and broken nails

are sometimes seen. The illness is usually named for the affected

physique half (i.e., tinea capitis [head], tinea corporis [body],

tinea cruris [groin], and tinea pedis [foot]) (Determine 48–1).

Tinea unguium, additionally known as onychomycosis, is a illness of

the nails, particularly toe nails. The nails develop into thickened,

damaged, and discolored.

Trichophyton tonsurans is the commonest reason for out-

breaks of tinea capitis in youngsters and is the principle reason for

endothrix (contained in the hair) infections. Trichophyton rubrum is

additionally a quite common reason for tinea capitis. Trichophyton schoen-

leinii is the reason for favus, a type of tinea capitis by which crusts

are seen on the scalp. Trichophyton species additionally trigger an inflam-

matory pustular lesion on the scalp known as a kerion. The marked

irritation is attributable to an intense T-cell–mediated response

to the presence of the fungus.

In some contaminated individuals, hypersensitivity causes dermato-

phytid (“id”) reactions (e.g., vesicles on the fingers). Id lesions

are a response to circulating fungal antigens; the lesions don’t

include hyphae. Sufferers with tinea infections present optimistic

pores and skin checks with fungal extracts (e.g., trichophytin).

Scrapings of pores and skin or nail positioned in 10% potassium hydroxide

(KOH) on a glass slide present septate hyphae beneath microscopy.

Cultures on Sabouraud’s agar at room temperature develop typical

hyphae and conidia. Tinea capitis lesions attributable to Microsporum

species could be detected by seeing fluorescence when the lesions

are uncovered to ultraviolet gentle from a Wooden’s lamp.

Therapy entails native antifungal lotions, corresponding to terbin-

afine (Lamisil), undecylenic acid (Desenex), miconazole (Micatin),

or tolnaftate (Tinactin). Oral griseofulvin (Fulvicin) or oral

itraconazole (Sporanox) may also be used. Tinea unguium can

be handled with efinaconazole answer utilized topically to the

nails. Prevention facilities on conserving pores and skin dry and funky.

Tinea Versicolor

Tinea versicolor (pityriasis versicolor), a superficial pores and skin infec-

tion of beauty significance solely, is attributable to Malassezia spe-

cies. The lesions are normally observed as hypopigmented areas,

particularly on tanned pores and skin in the summertime. There could also be slight

scaling or itching, however normally the an infection is asymptomatic. It

happens extra regularly in sizzling, humid climate. The lesions con-

tain each budding yeast cells and hyphae. Prognosis is normally

made by observing this combination in KOH preparations of pores and skin

scrapings. Tradition just isn’t normally finished. The remedy of selection

is topical miconazole, however the lesions generally tend to recur.

Oral antifungal medicine, corresponding to fluconazole or itraconazole, can

be used to deal with recurrences.

Tinea Nigra

Tinea nigra is an an infection of the keratinized layers of the pores and skin.

It seems as a brownish spot attributable to the melanin-like pig-

ment within the hyphae. The causative organism, Cladosporium

werneckii, is discovered within the soil and transmitted throughout damage.

In the USA, the illness is seen within the southern states.

Prognosis is made by microscopic examination and tradition of

pores and skin scrapings. The an infection is handled with a topical kerato-

lytic agent (e.g., salicylic acid).

SUBCUTANEOUS MYCOSES

These are attributable to fungi that develop in soil and on vegetation

and are launched into subcutaneous tissue by means of trauma.

Sporotrichosis

Sporothrix schenckii is a dimorphic fungus. The mildew type lives

on vegetation, and the yeast type happens in human tissue. When

spores of the mildew are launched into the pores and skin, usually by a

thorn, it causes a neighborhood pustule or ulcer with nodules alongside the

draining lymphatics (Determine 48–2). The lesions are usually

painless, and there’s little systemic sickness. Untreated lesions

might wax and wane for years. In human immunodeficiency virus

(HIV)-infected sufferers with low CD4 counts, disseminated

Chromomycosis

This can be a slowly progressive granulomatous an infection that’s

attributable to a number of soil fungi (Fonsecaea, Phialophora, Clado-

sporium, and so on.) when launched into the pores and skin by means of trauma.

These fungi are collectively known as dematiaceous fungi, so

named as a result of their conidia or hyphae are dark-colored, both

grey or black. Wartlike lesions with crusting abscesses lengthen

alongside the lymphatics. The illness happens primarily within the tropics

and is discovered on naked ft and legs. Within the scientific laboratory,

darkish brown, spherical fungal cells are seen in leukocytes or big

cells. The illness is handled with oral flucytosine or thiabenda-

zole, plus native surgical procedure.

Mycetoma

Soil fungi (Petriellidium, Madurella) enter by means of wounds on

the ft, fingers, or again and trigger abscesses, with pus discharged

by means of sinuses. The pus comprises compact coloured granules.

Actinomycetes corresponding to Nocardia could cause related lesions

(actinomycotic mycetoma). Sulfonamides might assist the acti-

nomycotic type. There isn’t any efficient drug in opposition to the fungal

type; surgical excision is really helpful.

SELF-ASSESSMENT QUESTIONS

1. Relating to ringworm and the dermatophytes, which one of many

following is most correct?

(A) The dermatophytes are molds and aren’t thermally dimorphic.

(B) The drug of selection for the remedy of ringworm lesions is

amphotericin B.

(C) The aim of the KOH prep is to watch fungal antigens

inside contaminated cells.

(D) The dermatophytid response refers back to the necrotic space typi-

cally seen within the middle of ringworm lesions.

(E) The principal reservoir of dermatophytes within the genus Tricho-

phyton is home animals corresponding to canines and cats.

2. Relating to sporotrichosis and Sporothrix schenckii, which one among

the next is most correct?

(A) The principle reservoir of Sporothrix is canine feces.

(B) Laboratory prognosis entails seeing a nonseptate mildew in an

aspirate of the lesion.

(C) Sporothrix is usually acquired by penetrating wounds sustained

whereas gardening.

(D) The remedy of selection for sporotrichosis is surgical removing

of the lesion as a result of there isn’t any efficient drug.

(E) Illness happens primarily in sufferers who’re poor within the

late-acting complement parts.

3. Your affected person is a 65-year-old lady with a 2-cm ulcerated lesion

on the palm of her hand that has been step by step getting larger

through the previous month. The lesion is barely barely tender and is

not purple, sizzling, or painful. A cautious historical past reveals that she was

making holly wreaths to be used at Christmas. (Holly leaves have

sharp factors.) She is afebrile and in any other case properly. An aspirate of

the lesion was obtained. Which one of many following would finest

help a prognosis of sporotrichosis?

(A) A tradition on blood agar at 25°C revealed white, beta-hemo-

lytic colonies.

(B) A methenamine silver stain examined within the gentle microscope

revealed budding yeasts.

(C) A KOH preparation examined within the gentle microscope revealed

septate hyphae.

(D) A tradition on Sabouraud’s agar at 37°C revealed a brownish

mycelium with inexperienced spores.

(E) An unstained pattern examined in the dead of night discipline microscope

revealed nonseptate hyphae.

4. Your affected person is a 10-year-old boy with tinea pedis (athlete’s ft).

Which one of many following is your best option of drug to deal with his

an infection?

(A) Amphotericin B

(B) Caspofungin

(C) Flucytosine

(D) Terbinafine

ANSWERS

(1) (A)

(2) (C)

(3) (B)

(4) (D)

SUMMARIES OF ORGANISMS

Temporary summaries of the organisms described on this chapter

start on web page 680. Please seek the advice of these summaries for a fast

assessment of the important materials.

PRACTICE QUESTIONS: USMLE &

COURSE EXAMINATIONS

Questions on the matters mentioned on this chapter could be discovered

within the Mycology part of Half XIII: USMLE (Nationwide Board)

Apply Questions beginning on web page 730. Additionally see Half XIV:

USMLE (Nationwide Board) Apply Examination beginning on