Disseminated bacillus Calmette-Guérin infections in patients with primary immunodeficiencies

Area of Science:

• Pathology
• Immunology
• Infectious Diseases

Background:

• Bacillus Calmette-Guérin (BCG) vaccination is a common prophylaxis against tuberculosis.
• Immunodeficiency can predispose individuals to disseminated BCG infection.
• BCG vaccination practices vary globally, with widespread use in some regions.

Purpose of the Study:

• To describe the pathologic findings in patients with disseminated BCG infection following vaccination.
• To correlate histologic features with the degree of host immunodeficiency.
• To highlight the importance of considering BCG dissemination in immunocompromised patients from endemic regions.

Main Methods:

• Analysis of biopsy and autopsy materials from four patients with BCG infection.
• Identification of Mycobacterium BCG strains in a reference laboratory.
• Histopathologic examination of affected tissues, including skin, systemic organs, and bone marrow.

Main Results:

• Patients presented with skin nodules, systemic organ lesions, and bone marrow involvement.
• Three patients had regional BCG lymphadenitis; one had disseminated BCG without local reaction.
• Histology showed diffuse histiocytic infiltrates with poorly formed granulomas and abundant acid-fast bacilli (AFB).
• Massive histiocytosis sometimes resembled a spindle cell neoplasm.
• Findings varied based on host immunocompetence, with unimpeded AFB proliferation in severe immunodeficiency.

Conclusions:

• Disseminated BCG infection can occur in individuals with severe combined or T-cell immunodeficiency.
• Histologic patterns reflect the host's immune status, with a lack of granuloma formation in severe cases.
• BCG dissemination should be considered in immunocompromised patients vaccinated in countries where BCG is practiced.