Dermatophytic and Subcutaneous Mycoses: Understanding Cutaneous Fungal Infections and Their Subdermal Affect
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,
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 (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 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).
These are attributable to fungi that develop in soil and on vegetation
and are launched into subcutaneous tissue by means of trauma.
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
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.
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.
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
(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
(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-
(B) A methenamine silver stain examined within the gentle microscope
revealed budding yeasts.
(C) A KOH preparation examined within the gentle microscope revealed
(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
(A) Amphotericin B
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 &
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