Histoplasmosis The 5 Minute Pediatric Consult


	Histoplasmosis

Hector L. Flores-Arroyo

Database
Differential Diagnosis
Data Gathering
Physical Examination
Laboratory Aids
Therapy
Follow-Up
Common Questions and Answers
Bibliography

DATABASE

DEFINITION

Infection of the lung caused by the fungus Histoplasma capsulatum.

CAUSES

Inhalation of spores of the dimorphic fungus Histoplasma capsulatum
Localized mononuclear cell infiltrate that may develop into a tuberculoid granuloma with multinucleated giant cells
Lesions can undergo caseation necrosis, fibrosis, and, ultimately, calcification.
Lesions usually localized to the lungs, though dissemination can occur.

GENETICS

No genetic implications

EPIDEMIOLOGY

The most common systemic fungal infection in the United States.
Organism has been found in soil, blackbird and pigeon roosts, chicken houses, caves, attics, and old buildings.
Endemic in the eastern and central United States, more specifically in the Mississippi and Ohio valleys, where 80% of the adults are skin test positive.
No human-to-human or animal-to-human transmission.
The symptoms depend on the immunological status of the host, as well as the size of the innoculum.
The incubation period is between 1 to 3 weeks.
Severe cases have been found to happen in the immunocompromised hosts as well as in children younger than 2 years of age.

COMPLICATIONS

In general, complications are rare.

Include:
- Tracheobronchial compression
- Mediastinal granuloma formation
- Fistula formation
- Pericarditis
- Mediastinal fibrosis
Disseminated disease involves:
- Skin
- Eyes
- Liver
- Spleen
- Bone marrow
- Heart
Severe form of histoplasmosis is seen in patients with immunodeficiencies who live in endemic areas.

DIFFERENTIAL DIAGNOSIS

Infections
- Pneumonia (viral, bacterial)
- Viral syndrome
- Tuberculosis
- Other fungal diseases: aspergillosis, blastomycosis, coccidiomycosis
- Sarcoidosis

DATA GATHERING

HISTORY

In children, severity of acute pulmonary histoplasmosis can vary:

Question: Upper respiratory symptoms, low grade fever, chest pain
Significance: Mild disease: 80% of patients affected; the course of the disease is 1 to 5 days. More than 95% of the patients are asymptomatic

Question: High fever, productive cough, chest pain, shortness of breath, hoarseness
Significance: Moderate disease: lasts approximately 15 days

Question: High fever, night sweats, weight loss, cough, chest pain, shortness of breath, hoarseness
Significance: Severe disease: lasts up to 3 weeks

PHYSICAL EXAMINATION

Finding: Flu-like signs and symptoms
Significance: Common presentations

Fever
Cough
Hepatosplenomegaly
Adenopathy
Pneumonitis
Skin lesions (erythema nodosum)
Disseminated histoplasmosis

LABORATORY AIDS

Test: Identification of organism
Significance: Histologic identification from sputum, blood, bone marrow, biopsy specimens, and/or cerebrospinal fluid

Test: Staining methods (if granulomas are present)
Significance: Gomori methenamine silver (GMS), Wright, Giemsa, periodic acid-Schiff (PAS)

Test: Culture of the organism in tissue specimens or peripheral blood smears

Test: Serologic studies

Test: Complement fixation
Significance: A single titer 1:32 is diagnostic; a four-fold increase in titers is diagnostic. This test is more sensitive than the immunodiffusion test, which is more specific.

Test: Precipitating antibodies
Significance: H band suggests active infection, M band less specific, presence of H and M bands highly diagnostic

Test: Skin testing
Significance: A positive reaction to the histoplasmin test may become reactive 2 to 6 weeks after the infection positive when area of induration <5 mm at 48 hours. This test is not recommended for diagnostic purposes.

IMAGING

Test: Chest radiograph
Significance: Normal in 75% of the patients with histoplasmosis

Most common radiologic changes include:
- Small 2- to 5-mm infiltrates in the lung bases
- Enlarged or calcified hilar nodes
- Buckshot calcifications seen in patients with large inoculurn
- Miliary pattern seen in patients with a high level of immunity
- Pleural effusions in 10% of adult films
- Calcified nodules in the liver and spleen

THERAPY

DRUGS

The uncomplicated cases of primary histoplasmosis of the lungs may not require medication therapy.
Patients with severe or disseminated disease or the immunocompromised may require treatment with antifungal agents. The recommended length of treatment is 6 weeks:
- Amphotericin B, 0.5 to 1.0 mg/kg/d IV for 2 to 6 weeks
- Ketoconazole, 6 to 8 mg/kg/d PO (400 mg/d is maximum dose) for 3 to 6 months
- Other effective agents include fluconazole and itraconazole, although the latter has not been approved for the use in children, it is effective in the treatment of HIV patients with severe histoplasmosis

FOLLOW-UP

WHEN TO EXPECT IMPROVEMENT

In mild-to-moderate cases not requiring drug therapy, usually 1 to 2 weeks
In cases requiring therapy, improvement is usually noted within 2 weeks.

PROGNOSIS

In most cases, prognosis is excellent.
90% mortality within 3 months in patients with acute disseminated histoplasmosis if left untreated.

PITFALLS

Can be difficult to distinguish between active disease and previous exposures in patients from endemic regions.

PREVENTION

Isolation of the hospitalized patient
- Must isolate from patients with immunodeficiencies, otherwise standard universal precautions

CONTROL MEASURES

None

COMMON QUESTIONS AND ANSWERS

Q: How can histoplasmosis be prevented?
A: Prevention can only be achieved by controlling the environmental factors in the affected areas; there are no vaccines for the prevention of histoplasmosis.

Q: Do patients with histoplasmosis need to be isolated?
A: No isolation of infected patients is required.

ICD-9-CM 115.90

BIBLIOGRAPHY

American Academy of Pediatrics. 1997 Red book: report of the Committee on Infectious Diseases. Evanston, IL; Academy of Pediatrics. 1997:277–278.

Bonner JR, Alexander WJ, Dismukes WE, et al. Disseminated histoplasmosis in patients with the acquired immune deficiency syndrome. Arch Intern Med 1984;144:2178–2181.

Davies SF. Serodiagnosis of histoplasmosis. Semin Respir Infect 1986;1:9–15.

Goodwin RA, Lloyd JE, Des Prez RM. Histoplasmosis in normal hosts. Medicine 1981;60:231–266.

Kanga J, Wilson HD. Pediatric respiratory disease: diagnosis and treatment. Philadelphia: WB Saunders, 1993:240–250.

Wheat J, French MLV, Kholer RB, et al. The diagnostic laboratory tests for histoplasmosis. Ann Intern Med 1982;97:680–685.

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