B. Histoplasmosis
Discussion
Chest radiographs demonstrate patchy air space opacities and
consolidation in the superior segment of the right lower lobe.
Concurrent chest CT shows segmental/sub-segmental consolidation in the
superior segment of the right lower lobe with scattered satellite
peripheral nodules and mediastinal lymphadenopathy. There is no pleural
effusion. The radiologic presentation is not specific and the
differential diagnoses include infections (viral, bacterial, or fungal),
pulmonary edema, hemorrhage, chronic interstitial lung disease such as
organizing and/or eosinophilic organizing pneumonia, sarcoidosis,
vasculitis, medication toxicity, and neoplasms.
Patient’s clinical presentation of fever and cough is typical for
infection, particularly in a very young adult. Pneumocystis pneumonia (Option D) seems unlikely given patient’s negative past medical history and immune-competent status. Klebsiella Pneumonia (Option C)
tends to be in higher prevalence in older patients with alcoholism and
debilitated hospitalized patients. Typical radiographic findings include
cavitary lesion with a bulging fissure sign, which is not present in
the current case. The dense consolidation, satellite nodules and
mediastinal lymph nodes demonstrated in this case are characteristics of
granulomatous disease, such as mycobacterial or fungal infections.
Tuberculosis is excluded given negative Quantiferon Gold test (Option A).
Patient was an animal science major and admitted to handling bats
recently. Patient was subsequently found to be positive for serum and
urine histoplasma antigen which eventually lead to the diagnosis of
acute pulmonary histoplasmosis (Option B)1. Other less common bat-related infections such as Ebola or Hantavirus were considered but no microbiologic evidence was found.
Histoplasmosis is a common endemic and systemic fungal infection in the North America2,3.
Some populations studies have shown that over 80% of young adults from
endemic regions of North America have been previously infected by Histoplasma capsulatum. In acute pulmonary histoplasmosis, majority of cases have no symptoms2,3.
Most common symptoms reported include fever, cough, dyspnea, chest
pain, malaise, headache, myalgia, dysphagia and abdominal pain.
Emphysematous changes, mediastinal granuloma, fibrosing mediastinitis
and broncholithasis are late stage manifestations. In immunocompetent
individuals, histoplasmosis infection is usually self-limited and no
treatment is required2,3,4.
Antifungal medications such as Itraconazole, Ketoconazole and
amphotericin B are treatment options. For mediastinal histoplasmosis
complicated by fibrosing mediastinitis, drug treatment is usually not
effective and surgery is often dangerous and unsuccessful. Vascular and
airway stents can be considered for treatment of stenosis secondary to
fibrosing mediastinitis5.
In our patient, persistent respiratory symptoms, positive
microbiology lab test and pulmonary consolidation of the imaging study
drove us to decide to initiate treatment. The patient underwent
treatment with itraconazole for one month (200mg bid, initial 3 days
tid) with significant improvement in her symptoms. She was then off of
the itraconazole for 3 weeks but her symptoms including worsening cough,
fever returned. Additional extensive work up for alternative diagnoses
was performed. Repeat Quantiferon Gold test remains negative. The
patient also had flexible bronchoscopy with EBUS lymph node biopsies.
BAL cytopathology was negative but histopathology on two of three EBUS
lymph node biopsies showed necrotizing granulomatous inflammation
and with a background polymorphous lymphoid cell population. There was
no evidence for malignant cells (Option E). Four fungal
cultures (and three acid-fast bacteria cultures, as well as Nocardia
and Actinomyces BAL cultures) were all without growth. The patient
subsequently resumed itraconazole again with improved symptoms.
Unfortunately, there were waxing and waning symptoms during the
following few months with 2 short hospitalizations. Follow up CT scan
(Images 5-6) obtained 10 months after the initial scans demonstrate
continued consolidation and cicatricial atelectasis of the superior
segment of the right lower lobe with small amount of pleural effusion.
There are enlarged anterior mediastinal and subcarinal lymph nodes with
stippled early calcification encasing right pulmonary artery with
borderline dilated main pulmonary artery (diameter greater than same
level aorta), but not at a magnitude to be suspicious for fibrosing
mediastinitis at this time. After recheck of patient’s immunostasis and
microbiology lab test, decisions were made to start voriconazole 300
mg BID with continued aggressive treatment of pulmonary histoplasmosis.
References
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Kauffman CA. Histoplasmosis. Clin Chest Med. 2009;30(2):217-225.
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Wheat LJ, Freifeld AG, Kleiman MB, et al. Clinical Practice
Guidelines for the Management of Patients with Histoplasmosis: 2007
Update by the Infectious Diseases Society of America. Clin Infect Dis. 2007;45(7):807-825.
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Rubin SA, Winer-Muram HT. Thoracic histoplasmosis. J Thorac Imaging. 1992;7(4):39-50.
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