Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (494 page)

   
Cutaneous
: Cutaneous infection is caused by direct inoculation of infectious mold into tissue or dissemination from the sites of primary infection. About 15% of cases of mucormycosis are cutaneous. Nodular lesions may show bruising with surrounding pallor. Lesions may be chronic or rapidly progressive. The extremities are most commonly involved, but 35–40% of cases occur on the head, neck, or thorax. The mortality is higher in central lesions.

   
Disseminated
: Disseminated infection occurs in about 5% of patients; the signs and symptoms depend on the extent of dysfunction of affected tissues. Specific organ disease may be apparent but nonspecific. Therefore, a high index of suspicion, based on patients underlying disease and clinical findings, is critical.

   Laboratory Findings

Histopathology
: Infected tissue is necrotic, hemorrhagic, thrombotic, or pale depending on the degree and type of vascular compromise. Inflammation is not prominent in acute infection. Angioinvasion may be seen.

Culture
: Specimens should be submitted for fungal culture, but cultures may be negative, depending on the location and type of infection and processing of specimens. Vigorous processing may damage hyphae, resulting in false-negative cultures. Therefore, when mucormycosis is suspected, the laboratory should be alerted to use gentle processing protocols, like gentle mincing of tissue rather than tissue homogenization. Cultures may be positive from acutely infected nasal sinus or turbinate tissue or nasal discharge. Cultures from CSF are rarely contributory. Mucormycosis cannot be excluded by negative cultures. In addition, positive cultures must be interpreted with caution to rule out possible contamination.

PARACOCCIDIOIDOMYCOSIS (
PARACOCCIDIOIDES BRASILIENSIS
)

   Definition

Paracoccidioidomycosis is caused by the thermally dimorphic fungus
Paracoccidioides brasiliensis
. This organism is endemic in wet, heavily vegetated, high-humidity areas of South America and Central America. The incidence of paracoccidioidomycosis is highest in Brazil.

   Who Should Be Suspected?

Most infections remain asymptomatic or mild, but clinical recovery may not be associated with microbiologic cure. Dormant infection may lead to recurrent, symptomatic infection at the time of acquired immunodeficiency. Disease is uncommon in children. Most symptomatic infections occur in men with occupations or other activities that put them in close contact with the environment. Symptoms are nonspecific and mimic TB, histoplasmosis, or other conditions. Symptoms include fever, chronic cough, sputum production, dyspnea, chest pain, weight loss, and malaise. The risk of infection is increased in patients who smoke, those who are alcoholic, or those who have AIDS. Person-to-person transmission does not occur.

   Laboratory Findings

Direct detection
: Deep respiratory specimens, CSF, or tissue from granulomas, ulcers, lymph nodes, or other infected sites show the characteristic large yeast cells with multiple narrow-based buds (mariner’s wheel). A mixed granulocytic, monocytic response is typical.

Culture
: Routine fungal culture yields growth in the mold phase, which shows characteristic, but not specific, mycelial and conidial morphology.

Serology
: The diagnosis is supported by demonstration of specific antibodies using CF, ID, and other antibody detection techniques. Successful therapy is associated in significant decrease in antibody titers when acute and convalescent serum samples are tested. The quantitative ID assay is sensitive (>95%) and specific (near 100%) for diagnosis and is recommended.

Routine laboratory
: Morning cortisol levels and ACTH stimulation testing are recommended because of the frequency of adrenal gland involvement. Routine laboratory testing to evaluate the function of infected organs is recommended. Common findings include anemia, eosinophilia, hypoalbuminemia, hyperbilirubinemia, hypergammaglobulinemia, and mildly elevated transaminases.

PNEUMOCYSTIS JIROVECII
(FORMERLY
P. CARINII
)

See Chapter
13
, Respiratory, Metabolic, and Acid–Base Disorders.

SPOROTRICHOSIS

   Definition

Sporotrichosis is a subacute to chronic infection caused by the thermally dimorphic fungus
Sporothrix schenckii
. Sporotrichosis occurs mainly in North and South America and Japan, but scattered cases are seen worldwide. In the environment, this organism exists in its mold phase and is associated with soil and thorned plants, like roses. Infection is transmitted most commonly by traumatic inoculation or inoculation of nonintact skin surfaces. Most infections, therefore, are related to outdoor recreational or occupational activities. Infection may disseminate from the site of primary infection.

   Who Should Be Suspected?

Extracutaneous infection is most commonly seen in patients with underlying illnesses that may compromise immune function, including alcoholism, DM, COPD, and AIDS (uncommon).

   
Lymphocutaneous sporotrichosis
: A papular lesion, with overlying erythema, initially forms at the site of inoculation. The lesion commonly ulcerates. Similar lesions develop along the lymphatic drainage path from the primary site of infection. The lesions of lymphocutaneous sporotrichosis are usually only minimally painful. Systemic symptoms are usually absent.