Blastomycosis - Manifestations, Diagnosis, and Treatment

Introduction:

Blastomycosis is a fungal infection with pulmonary involvement caused by breathing in the spores of a dimorphic fungus called Blastomyces dermatitidis. It spreads and also causes extrapulmonary disease. Blastomyces dermatitidis exists as a mold in the ambient temperature found in soil and also in decaying, moist, acidic organic material commonly found around river banks. After inhalation of spores, it reaches the lungs, and spores are converted into large yeasts of about size 15 to 20 micrometers, which later form into broad-based buds. After transformation into buds, they may either remain localized in the lungs or disseminate (spread) hematogenously.

What Are the Signs and Symptoms of Blastomycosis?

1. The pulmonary involvement of this infection manifests as asymptomatic or symptomatic cases. It can occur suddenly and may develop into a chronic, progressive infection. The symptoms of this infection include:

• A dry or productive cough.

• Chest pain.

• Dyspnea.

• Low-grade fever.

• Chills.

• Sweats.

• Pleural effusion may occur.

• Acute respiratory distress syndrome.

2. The extrapulmonary symptoms depend on the organs involved. The hematogenous spread of this infection can cause infection in various other organs such as skin, epididymides, testes, kidneys, seminal vesicles, vertebrae, long bones, prostate, central nervous system, thyroid, oral or nasal mucosa, bone marrow, and lymph nodes.

3. In the case of involvement of the central nervous system, the infection can manifest as epidural abscess, meningitis, or brain abscess.

4. If bones are involved, overlying structures are swollen, tender, and warm.

5. If genital organs are affected, genitourinary manifestations are deep. Perineal discomfort, epididymal swelling, or prostatic tenderness are observed during the rectal examination.

6. Among all other organs, the skin is the most commonly involved site of dissemination.

7. The skin lesions may be single or multiple with or without the pulmonary involvement.

8. Painless abscess varying in size from pinpoint to one millimeter in diameter. In addition to this, irregular wart-like structures called papillae arise, from which bullae may develop.

9. In a fully developed lesion, it appears as an elevated verrucous patch of greater than two centimeters with a purplish-red, abscess-studded border. In the presence of bacterial superinfection, ulceration may occur.

What Are the Other Findings of the Physical Examination?

• Patients with asymptomatic conditions account for about 50 % of the infected persons.

• Acute respiratory distress syndrome can occur in cases of immunocompromised or old-age people.

• Acute or chronic forms of pneumonia can occur.

• Extrapulmonary conditions with skin lesions such as papules that transform into crusted, vegetative plaques resulting in ulceration.

• Other findings include lymphadenitis and lymphadenopathy.

• Extrapulmonary lesions involving bone can account for about 25 % of cases and are particularly lytic in nature.

• Generally, osteomyelitis can involve any bones, but in this condition, the pelvis and lower spine are most commonly involved.

• Prostatitis, orchitis, or epididymitis are other findings of extrapulmonary disease.

What Can Be the Prognosis of Blastomycosis?

The prognosis of the healthy individual affected with blastomycosis is generally excellent, but in the case of immunocompetent people, the prognosis can probably be good with variations. Overall, the successful treatment of this condition is reported to be approximately around 80 % to 95 % of cases. Poor prognosis is observed in cases of immunocompromised patients affected with blastomycosis.

How to Diagnose Blastomycosis?

Culture and cytopathology are the usual and standard tests for the diagnosis of blastomycosis. One of the fastest and best ways to diagnose is under direct examination of the broad-based budding yeast using a microscope. In the culture technique, identification is not evident for two to four weeks, and it includes invasive procedures such as bronchoscopy or tissue biopsy to reach specimens. Recently, the rapid identification of Bacillus dermatitis from the clinical specimen has been determined with the help of molecular DNA probes. A chemiluminescent DNA probe assay is widely used and provided within hours once there is adequate growth.

• Chest X-ray: The findings are non-specific and may reveal scattered centrilobular nodules and areas of dense consolidation.

• Computed Tomography (CT) Scan: A computed tomography scan is not always necessary in the case of blastomycosis, but these details can provide a better definition of the abnormalities present in the radiograph.

How to Manage Blastomycosis?

Antifungal Treatment:

• In patients with mild to moderate pulmonary disease, oral Azoles are prescribed (for example, Itraconazole).

• In patients with moderate to severe extrapulmonary disseminated disease or immunocompromised conditions, Amphotericin B is initially given with a step down to an oral Azole after evident clinical improvement.

• Amphotericin B is prescribed in patients with the central nervous system and in pregnant women.

• Amphotericin B and Itraconazole are the main drugs of choice used in the treatment of blastomycosis.

• Alternative antifungal agents such as Fluconazole, Ketoconazole, and Voriconazole are used. Both Fluconazole and Voriconazole possess good cerebrospinal fluid penetration.

• Voriconazole is effectively used in patients with immunocompromised conditions and central nervous system disorders.

• Except for life-threatening cases, Itraconazole is involved in all forms of the disease. A dosage of 600 milligrams is given orally daily for three days, followed by 200 milligrams to 400 milligrams per day up to six to twelve months. Itraconazole has relatively low side effects and low toxicity but with good efficacy. It is important that gastric acidity is needed for its better absorption.

• Azoles are contraindicated in pregnancy.

• Amphotericin B is recommended in severe life-threatening cases at a high dosage of 0.7 to 1 milligram per kilogram per day to a total dose of 1.5 to 2 grams.

• In the cases of pregnant women and the central nervous system involved in blastomycosis, liposomal Amphotericin B is used at a dosage of 3 to 5 milligrams per kilogram per day as an alternative drug of choice.

• In long-term usage of Amphotericin, several cases are reported with adverse effects such as renal impairment, anemia, hypokalemia, fever, chills, thrombophlebitis at the injection site, and nausea.

Conclusion:

The overall outlook for healthy patients with blastomycosis is good, but the recovery may be prolonged. In the case of immunocompromised individuals, the outcomes are unpredictable. The primary goal in the management is to treat patients with mild or moderate diseases to prevent the spreading or dissemination of the disease to other organs of the body and also to prevent the recurrence of the disease.