Fungal Infections Merck Manual Chapter 185

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The Merck Manual of Medical Information--Home Edition

Section 17. Infections

Chapter 185

Fungal Infections

A type of plant, fungi include molds and mushrooms. Spores of many

fungi are everywhere in the environment. Often these spores float in

the air. Of the wide variety of spores that land on the skin or are

inhaled into the lungs, some can cause minor infections, which only

rarely spread to other parts of the body. A few types of fungi, such

as the Candida strains, can live normally on body surfaces or in the

intestines. These normal body inhabitants only occasionally cause

local infections of the skin, vagina, or mouth, but seldom do more

harm. Occasionally, however, certain strains of fungi can produce

severe infections of the lungs, the liver, and the rest of the body.

Risk Factors for Developing Fungal Infections

Therapy that suppresses the immune system

Anticancer drugs (chemotherapy)

Corticosteroids and other immunosuppressant drugs

Diseases and conditions

AIDS

Kidney failure

Diabetes

Lung disease, such as emphysema

Hodgkin's disease or other lymphomas

Leukemia

Extensive burns

Fungi have a special tendency to cause infections in people with a

compromised immune system. For example, people with AIDS or those

undergoing treatment for cancer are more likely to develop serious

fungal infections. Sometimes, people with impaired immunity develop

infections caused by types of fungi that seldom, if ever, inflict

harm in people whose immune systems are functioning normally. Such

infections include mucormycosis and aspergillosis. (see page 935 in

Chapter 188, Infections in People With Impaired Defenses)

Some fungal infections are more common in certain geographic areas.

For example, in the United States, coccidioidomycosis occurs almost

exclusively in the Southwest, whereas histoplasmosis is common in

the East and Midwest, especially in the Ohio and Mississippi River

valleys. Blastomycosis occurs only in North America and Africa.

Because many fungal infections develop slowly, months or years may

pass before a person realizes medical attention is needed. These

infections may be difficult to treat, and treatment usually takes a

long time. A variety of antifungal drugs are available. (see box,

page 851)

Histoplasmosis

Histoplasmosis is an infection caused by the fungus Histoplasma

capsulatum that occurs mainly in the lungs but can sometimes spread

to all parts of the body.

The spores of Histoplasma are present in the soil, particularly in

certain eastern and midwestern states of the United States. Farmers

and others working with infected soil are most likely to inhale the

spores. Severe disease may result when large numbers of spores are

inhaled. People with human immunodeficiency virus (HIV) infection

are more likely to develop histoplasmosis, especially the form that

spreads throughout the body.

Symptoms and Prognosis

Most people who are infected don't have any symptoms. However, in

those who show signs of infection, histoplasmosis occurs in one of

three forms: the acute form, the progressive disseminated form, or

the chronic cavitary form.

In the acute form, symptoms usually appear 3 to 21 days after a

person inhales the fungal spores. The person may feel sick and have

a fever and a cough. Symptoms usually disappear without treatment in

2 weeks and rarely last longer than 6 weeks. This form of

histoplasmosis is seldom fatal.

The progressive disseminated form doesn't normally affect healthy

adults. It usually occurs in infants and in people who have an

impaired immune system (such as those with AIDS). Symptoms may

worsen either very slowly or extremely rapidly. The liver, spleen,

and lymph nodes may enlarge. Less commonly, the infection causes

ulcers in the mouth and intestines. In rare cases, the adrenal

glands may be damaged, causing 's disease. (see page 712 in

Chapter 146, Adrenal Gland Disorders) Without treatment, the

progressive disseminated form of histoplasmosis is fatal in 90

percent of people. Even with treatment, death may occur rapidly in

people with AIDS.

The chronic cavitary form is a lung infection that develops

gradually over several weeks, producing a cough and increased

difficulty in breathing. Symptoms include weight loss, a feeling of

illness (malaise), and a mild fever. Most people recover without

treatment within 2 to 6 months. However, breathing difficulties may

gradually worsen, and some people may cough up blood, sometimes in

large amounts. Lung damage or bacterial invasion of the lungs

eventually may cause death.

Diagnosis and Treatment

To make the diagnosis, a doctor obtains samples from an infected

person's sputum, lymph nodes, bone marrow, liver, mouth ulcers,

urine, or blood. These samples are then sent to a laboratory for

culture and analysis.

People with the acute form of histoplasmosis rarely require drug

treatment. Those with the progressive disseminated form, however,

often respond well to treatment with amphotericin B given

intravenously or to itraconazole given orally. In the chronic

cavitary form, itraconazole or amphotericin B may eliminate the

fungus, although the destruction caused by the infection leaves

behind scar tissue. Breathing problems similar to those caused by

chronic obstructive pulmonary disease usually remain. Therefore,

treatment should begin as soon as possible to limit lung damage.

Coccidioidomycosis

Coccidioidomycosis (San Joaquin fever, valley fever) is an infection

caused by the fungus Coccidioides immitis that usually affects the

lungs.

Coccidioidomycosis occurs either as a mild lung infection that

disappears without treatment (the acute primary form) or as a

severe, progressive infection that spreads throughout the body and

is often fatal (the progressive form). The progressive form is often

a sign that the person has a compromised immune system, usually

because of AIDS.

The spores of Coccidioides occur in soil in certain areas of North

America, Central America, and South America. Farmers and others who

work with soil are most likely to inhale the spores and become

infected. People who become infected while traveling may not develop

symptoms of the disease until after they leave the area.

Symptoms

Most people with the acute primary form of coccidioidomycosis have

no symptoms. If symptoms develop, they appear 1 to 3 weeks after the

person becomes infected. The symptoms are mild in most people and

may include a fever, chest pain, and chills. The person also may

cough up sputum and occasionally blood. Some people develop desert

rheumatism--a condition consisting of inflammation of the surface of

the eye (conjunctivitis) and joints (arthritis) and the formation of

skin nodules (erythema nodosum).

The progressive form of the disease is unusual and may develop

weeks, months, or even years after the acute primary infection or

after living in an area where the disease is common. Symptoms

include a mild fever and losses of appetite, weight, and strength.

The lung infection may worsen, causing increased shortness of

breath. The infection also may spread from the lungs to the bones,

joints, liver, spleen, kidneys, and the brain and its lining.

Diagnosis

A doctor may suspect coccidioidomycosis if a person who lives in or

has recently traveled through an infected area develops these

symptoms. Samples of sputum or pus are taken from the infected

person and sent to a laboratory for analysis. Blood tests may reveal

the presence of antibodies against the fungus. Such antibodies

appear early but disappear in the acute primary form of disease; the

antibodies persist in the progressive form.

Prognosis and Treatment

The acute form of coccidioidomycosis usually clears up without

treatment, and recovery usually is complete. However, people with

the progressive form are treated with intravenous amphotericin B or

oral fluconazole. Alternatively, the doctor may treat the infection

with itraconazole or ketoconazole. Although drug treatment can be

effective in localized infections, such as those in skin, bones, or

joints, relapses often occur after treatment is stopped. The most

serious types of progressive disseminated coccidioidomycosis are

often fatal, especially meningitis (infection of the membranes of

the brain and spinal cord). If a person develops meningitis,

fluconazole is used; alternatively, amphotericin B may be injected

into the spinal fluid. Treatment must be continued for years, often

for the rest of the patient's life. Untreated meningitis is always

fatal.

Blastomycosis

Blastomycosis (North American blastomycosis, Gilchrist's disease) is

an infection caused by the fungus Blastomyces dermatitidis.

Blastomycosis is primarily a lung infection, but occasionally it

spreads through the bloodstream. Spores of Blastomyces probably

enter the body through the respiratory tract when they are inhaled.

It is not known where in the environment the spores originate, but

beaver huts were linked to one outbreak. Most infections occur in

the United States, chiefly in the Southeast and the Mississippi

River valley. Infections have also occurred in widely scattered

areas of Africa. Men between the ages of 20 and 40 are most commonly

infected. The disease is rare in people with AIDS.

Symptoms and Diagnosis

Blastomycosis of the lungs begins gradually with a fever, chills,

and drenching sweats. A cough that may or may not bring up sputum,

chest pain, and difficulty in breathing may develop. Although the

lung infection usually worsens slowly, it sometimes gets better

without treatment.

The disseminated form of blastomycosis may affect many areas of the

body. A skin infection may begin as small, raised bumps (papules),

which may contain pus (papulopustules). The papules and

papulopustules last for a short time and spread slowly. Raised,

warty patches then develop, surrounded by tiny, painless abscesses--

some that are the size of a pinpoint. Bones may develop painful

swellings. In men, painful swelling of the epididymis (a cordlike

structure attached to the testes) or deep discomfort from an

infection of the prostate gland (prostatitis) may occur.

A doctor can make the diagnosis by examining a sample of sputum or

infected tissue, such as skin, under the microscope. If fungi are

seen, the sample can be cultured and analyzed in a laboratory to

verify the diagnosis.

Treatment

Blastomycosis may be treated with intravenous amphotericin B or oral

itraconazole. With treatment, the person begins to feel better in a

week, and the fungus disappears rapidly. Without treatment, the

infection slowly worsens and leads to death.

Candidiasis

Candidiasis (candidosis, moniliasis) is an infection caused by

strains of Candida, especially Candida albicans.

Infection of the mucous membranes, as occurs in the mouth or vagina,

is common in people with a normal immune system. (see pages 946 in

Chapter 189, Sexually Transmitted Diseases and 980 in Chapter 202,

Fungal Skin Infections) However, these infections are more common or

persistent in people with diabetes or AIDS and in pregnant women.

People with an impaired immune system commonly develop candidiasis

that spreads throughout the body. People at risk of developing an

infection in the bloodstream (candidemia) include those with a low

white blood cell count--which can be caused by leukemia or by

treatment for other cancers--and those who have a catheter placed in

a blood vessel. An infection of the heart valves (endocarditis) may

result from surgery or other invasive procedures involving the heart

and blood vessels.

Symptoms and Diagnosis

Symptoms of candidiasis vary, depending on which tissue is infected.

For example, infection of the mouth (thrush) causes creamy, white,

painful patches to form inside the mouth. Patches in the esophagus

can make it difficult for a person to swallow or eat. An infection

of the heart valves can cause a fever, a heart murmur, and

enlargement of the spleen. An infection of the retina (the light-

sensitive membrane on the inner surface of the back of the eye) can

cause blindness. An infection of the blood (candidemia) or kidney

can cause a fever, very low blood pressure (shock), and a decrease

in urine production.

Many candidal infections are apparent from the symptoms alone. For a

definite diagnosis, a doctor must be able to see the fungi in a skin

sample under a microscope. Samples of blood or spinal fluid that

have been cultured may also reveal the presence of the Candida fungi.

Prognosis and Treatment

When candidiasis occurs only in the mouth or vagina, antifungal

drugs may be applied directly to the area, or fluconazole can be

taken orally. Candidiasis that has spread throughout the body is a

severe, progressive, and potentially fatal disease that usually is

treated with intravenous amphotericin B, although fluconazole is

effective for some people.

Certain medical conditions, such as diabetes, can worsen candidiasis

and must be controlled to help eradicate the infection.

Sporotrichosis

Sporotrichosis is an infection caused by the fungus Sporothrix

schenckii.

Sporothrix is typically found on rosebushes, barberry bushes,

sphagnum moss, and other mulches. Most often, farmers, gardeners,

and horticulturists are infected.

Sporotrichosis usually affects the skin and nearby lymph vessels.

Occasionally, the lungs or other tissues may be infected.

Symptoms and Diagnosis

An infection of the skin and nearby lymph vessels typically starts

on a finger as a small, nontender nodule that slowly enlarges and

then forms a sore. Over the next several days or weeks, the

infection spreads through the lymph vessels that lead from the

finger through the hand and arm to the lymph nodes, forming nodules

and sores along the way. Usually, the person has no other symptoms.

An infection of the lungs may cause pneumonia, with a slight chest

pain and cough, usually in people who have some other lung disease,

such as emphysema. Less commonly, an infection may occur in other

parts of the body, such as the bones, joints, muscles, or eyes. Very

rarely, an infection occurs in the spleen, liver, kidney, genitals,

or brain.

The characteristic nodules and sores may lead a doctor to suspect

sporotrichosis. The diagnosis is confirmed by culturing and

identifying Sporothrix from samples of infected tissue.

Treatment

Sporotrichosis that affects the skin usually spreads very slowly and

is seldom fatal. The skin infection is treated with itraconazole

taken orally. Oral potassium iodide may be prescribed instead, but

it is not as effective and causes side effects in most people, such

as rash, runny nose, and inflammation of the eyes, mouth, and

throat. For life-threatening, body-wide infection, amphotericin B is

given intravenously, but oral itraconazole may prove to be as good

or better as it is tested in more and more cases.