Cryptococcal pneumonia and meningitis in a renal transplant recipient with a false negative serum cryptococcal...

Area of Science:

• Infectious Diseases
• Mycology
• Nephrology

Background:

• Cryptococcal infections pose significant risks for immunocompromised patients, particularly those with a history of organ transplantation.
• Renal transplant recipients are susceptible to opportunistic infections like cryptococcosis, which can manifest as meningitis or pulmonary disease.

Observation:

• A case of cryptococcal meningitis and pulmonary disease in a renal transplant recipient is presented.
• Diagnosis was confirmed by positive blood cultures for *Cryptococcus neoformans* and cryptococcal antigen (CrAg) detection in cerebrospinal fluid (CSF) via lateral flow assay (LFA).

Findings:

• The initial serum CrAg test yielded a false-negative result due to the postzone phenomenon, where excess antigen inhibited antibody complex formation.
• This phenomenon, typically observed in CSF, was rarely reported in serum samples from non-HIV infected patients.

Implications:

• The postzone phenomenon can lead to delayed diagnosis and treatment of cryptococcal infections, even with sensitive diagnostic assays.
• Clinicians should maintain a high index of suspicion for cryptococcosis in immunocompromised patients, especially transplant recipients, and consider repeat or alternative testing if initial results are discordant with clinical presentation.
• This case underscores the importance of recognizing rare diagnostic pitfalls in infectious disease management.