Coccidioidomycosis
Introduction: This is a fungal infection, which is caused
by Coccidioides immitis. It is also known under the names "valley
fever" or "San Joaquin fever"). It occurs in the southwest
of the US (Texas west of El Paso, New Mexico, Arizona and the central
valley of California). It also occurs in Mexico, Central America and Argentina.
Infection is due to inhalation of dust containing the spores of C.immitis. There
is a complicated
cycle the organism goes through. The endospores are inhaled into the human
host. There is a certain incubation time, which makes it often confusing
in the traveling public to know exactly where this fungal infection came from.
Similar to other inhaled fungal infections the spores get activated in the lungs
by the temperature shift from the outside to the body temperature. With primary
coccidioidomycosis the spores transform in the lungs into large
"spherules", which contain multiple endospores. As the spherules enlarge
there comes a point where they rupture and the cycle repeats itself with many
more new spherules growing. The lung tissue reacts to the foreign pathogen by
forming inflammatory granulation tissue around the areas where spherules
are present. Eventually this forms scar tissue and leads to cavities similar to
tuberculosis of the lungs, which may be visible on chest
X-rays. Eventually, like with blastomycosis or histoplasmosis the
disease can change from the primary form, which is confined to the lungs, to a
disseminated form, called progressive coccidioidomycosis.
This usually requires a weak immune system such as in AIDS patients , in chemotherapy
patients who are treated for cancer, or in certain ethnic groups (Filipinos, black
and native Americans, Orientals and Hispanics) who are genetically more susceptible.
Similar to the other fungal disseminated infections the disease in this case is
spreading into the lymph glands, spleen, bone marrow, vital organs including the
brain. Signs and symptoms: Symptoms in the beginning
of the primary coccidioidomycosis may be absent. However, as the disease
is getting established there likely will be flu-like symptoms with a fever and
cough. There can be chills, coughing up of blood and chest pains. Some patients
develop an allergic reaction to the fungal infection, which manifests itself as
redness in the eyes (conjunctivitis), joint pains (arthritis), a skin rash with
red marks of multiple shapes (erythema multiforme) and a painful swelling over
the shins, called erythema nodosum. Symptoms of progressive
coccidioidomycosis could occur only months or years after the
primary infection. This occurs more in men and is often associated with AIDS or
other severe immune deficiencies. Weight loss and shortness of breath from lung
fibrosis due to the long standing primary form of the disease are common. This
is associated with Bluish discoloration of the skin (cyanosis), shortness of breath
and a chronic cough with phlegm consisting of yellow-greenish mucous mixed with
blood. Other symptoms are dependent on where the disease has spread. Inner organs
such as liver or kidneys can get infected, but it can also spread into the brain
(encephalitis) or into the membranes around the brain (meningitis). Bones and
joints or the skin may also get infected. Usually by that time the patient is
extremely ill and would have been examined by a physician in the hospital setting.
An infection specialist would be consulted who would have made the diagnosis,
if that disease was not already diagnosed before. Diagnostic tests:
There are several diagnostic tests to diagnose coccidioidomycosis.
Body fluids, phlegm or tissue specimens can be set up for culture and the laboratory
can report the result as positive or negative for C. immitis. Another possibility
is to stain tissue samples or samples of body fluid directly with special stains
and look under the microscope for spherules containing endospores, a very specific
appearance, which will make the diagnosis, if present. Finally, a blood test where
IgG antibodies are measured using a complement fixation test, is very useful in
detecting the disease, as the titers can predict how active the disease is (see
table, based on data from Ref.1, p. 1215).
| Antibody titer test
to diagnose coccidioidomycosis | | Anticoccidioidal
antibody titer : | Comments: |
| more than 1:4 | positive
for infection (likely confined to lungs only) |
| more than 1:32 | high
probability of progressive coccidioidomycosis | In
immunosuppressed patients the titers may be lower than would otherwise be expected.
It might appear as if they are confined to the lungs only, but the clinician
has to then rely on clinical judgment and a number of more tests in order to know
whether the immune system is weak. With neurological signs of meningitis a CSF
sample is taken by lumbar puncture and this is also examined with the antibody
titer test. This is a better indicator (it is more sensitive) than to culture
CSF (could be false negative). Other tests would involve X-rays such as CT
scans, bronchoscopy and biopsy. Treatment:
For milder cases oral therapy with fluconazol (brand name: Diflucan) or
itraconazole (brand name: Sporanox) is given. The end point of treatment is reached
when repeat blood tests for the complement fixation titer are negative. Serious
infections are usually treated with intravenous amphotericin B. AIDS patients
need maintenance therapy with itraconazole (brand name: Sporanox). Meningitis
cases have to be treated longterm by the specialist (neurologist) with intrathecal
antifungal medicine and often for month, years or lifelong. Bone marrow
infection in bones is called "osteomyelitis" and this is another condition,
which is very frustrating to treat. The orthopedic surgeon may have to remove
the infected bone to cure this condition. Longterm antifungal therapy is warranted
in these cases as well (Ref. 1, p. 1216). |
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