Pulmonary Histoplasmosis Syndromes: Recognition, Diagnosis, and Management

Abstract

Pulmonary manifestations are the hallmark of histoplasmosis. Clinical syndromes range from asymptomatic infection to diffuse alveolar disease causing respiratory difficulty and even death. Serologic tests for antibodies and antigen detection are especially helpful in the diagnosis of histoplasmosis but are frequently overlooked. Detection of Histoplasma capsulatum antigen in bronchoalveolar lavage fluid may be particularly helpful in patients with acute pulmonary histoplasmosis or disseminated disease with pulmonary involvement. Topics of special importance for pulmonary disease specialists include the approach to the exclusion of histoplasmosis in the evaluation of patients with suspected sarcoidosis, differentiation of pulmonary histoplasmosis and malignancy in those with lung masses or mediastinal lymphadenopathy, and recognition and management of chronic pulmonary and mediastinal manifestations of histoplasmosis. Although histoplasmosis is mild and self-limited in most healthy individuals, antifungal therapy is indicated in those with acute diffuse pulmonary infection, chronic pulmonary histoplasmosis, progressive disseminated disease, and perhaps mediastinal adenitis accompanied by obstructive symptoms. Antifungal therapy to prevent reactivation of histoplasmosis during immunosuppressive therapy, or transition of mediastinal adenitis to fibrosing mediastinitis, although controversial, is not recommended. Several new drugs active against H. capsulatum offer alternatives in patients failing or intolerant of current therapies.

Histoplasmosis: a Clinical and Laboratory Update

“…Rales are heard in a minority of patients. Chest radiographs show a patchy pneumonia in one or more lobes; enlarged hilar and mediastinal lymph nodes are frequently noted (51,156). Improvement is prompt in the majority of cases, but in some patients, fatigue may linger for several months.…”

The Use of Endobronchial Ultrasound in the Diagnosis of Subacute Pulmonary Histoplasmosis

“…In SPH, the diagnosis can be challenging as most often these patients have nonspecific symptoms and findings that have a broad differential diagnosis. Although >90% of histoplasmosis infections are asymptomatic, mediastinal/hilar lymphadenopathy and associated nonspecific symptoms may be present in 5-10% of immunocompetent patients [2]. Currently, testing for antibodies by immunodiffusion or complement fixation technique is considered more sensitive for SPH than tests for an antigen, as fungal burden is low and pulmonary infection is often very localized in immunocompetent patients [3].…”

“…A dedicated aspiration needle (ViziShot, Olympus) was used to obtain specimens. The needle gauge, aspiration site, and the number of passes obtained [1,2,4] were performed at the discretion of the bronchoscopist. An on-site adequacy assessment was not available.…”

“…Approximately 250,000 individuals are infected annually but clinical manifestations of histoplasmosis occur in less than 5% [1]. Infections are sporadic, although large outbreaks of histoplasmosis may occur and histoplasmosis remains the most common cause for hospitalization amongst the endemic mycoses [2]. The morbidity and mortality of histoplasmosis are related to the duration and extent of systemic infection as well as underlying comorbidities.…”

“…Serology for histoplasmosis can be useful since the patient has often been infected for greater than one month allowing for a humoral immune response. High initial titers or rising titers over time are strongly suggestive of current or very recent infection, while a single low titer (<1 : 8) may suggest infections any time in the past [2].…”