Make the Diagnosis: Flu Symptom Surprise

Classical histoplasmosis, also known as Darling disease, small-form histoplasmosis, American histoplasmosis, cave disease, Ohio valley disease, or reticuloendotheliosis, is a systemic infection caused by the thermally dimorphic fungus Histoplasma capsulatum var. capsulatum. The yeast phase is present in tissue.

Classical histoplasmosis is endemic to the Ohio/Mississippi River Valley, South and Central America, northern South America, and Brazil, Argentina, Uruguay, and Paraguay.

Bird and bat excrement enhance the growth of the organism in the soil. Initially, microconidia are inhaled into the lungs where they transform into yeast forms.

There are three forms of the disease: pulmonary (acute and chronic), disseminated (acute and chronic), and primary cutaneous histoplasmosis.

Pulmonary:

In acute pulmonary histoplasmosis, the patient presents with cough, chest pain, fever, and occasionally a rash caused by immune complexes (erythema multiforme, toxic erythema, or erythema nodosum).

Chronic pulmonary histoplasmosis resembles pulmonary tuberculosis and is not usually associated with skin findings.

Disseminated:

In patients with acute disseminated histoplasmosis, the fungus spreads to other organs such as the liver, spleen, and bone marrow. This form commonly is seen in immunocompromised patients. Skin rash is more common in the disseminated form. Severe weight loss, fever, anemia, and hepatosplenomegaly can result.

Chronic disseminated histoplasmosis commonly appears months after a patient has left an endemic area. Patients may present with oral or pharyngeal ulcerations or with adrenal insufficiency after adrenal infiltration.

Disseminated histoplasmosis may be complicated by central nervous system infection in 5%-10% of cases and can manifest as meningitis, endocarditis, or pericarditis.

Cutaneous:

Primary cutaneous histoplasmosis is rare and occurs after trauma to the skin with an infected instrument. This may present as a nodule or indurated ulcer with associated lymphadenopathy.

In general, people at higher risk of exposure to infected soils include spelunkers, construction workers, and agricultural workers. Risk factors for systemic histoplasmosis include many immunosuppressed states. Disseminated histoplasmosis is considered as an AIDS-defining illness. AIDS patients with histoplasmosis usually present with weight loss and fever.

What To Look For: Pulmonary:

In acute pulmonary histoplasmosis, look for nonspecific reactive changes such as erythematous macules and papules or targetoid erythematous macules on the trunk or extremities (erythema multiforme) or tender red-brown nodules over the shins and extremities (erythema nodosum).

Chronic pulmonary histoplasmosis has no associated skin findings.

In acute disseminated histoplasmosis, look for erythematous papules and umbilicated papules, small nodules, or molluscum-like lesions. Shallow ulcers and crusted papules may develop later. Folliculitis-like and rosacea-like lesions have been reported.

In chronic disseminated histoplasmosis, look for oral ulcers, which are common. Ulcers may also occur anywhere along the gastrointestinal tract from the mouth to the colon. Plaques, nodules, and ulcers of the tongue, buccal mucosa, larynx, or lips may be seen in some patients.

In primary cutaneous histoplasmosis, look for an indurated papule or nodule at the trauma site, which sometimes may ulcerate and crust. Local lymphadenopathy.

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