Abstract
Opportunistic infections of the central nervous system are classically associated
with immunosuppression arising from infection with human immunodeficiency virus and
with various hematologic malignancies. However, over the past few years, they are
increasingly associated with transplantation and various immunosuppressive treatments
used to treat autoimmune diseases. They cause significant morbidity and mortality
and remain a diagnostic challenge due to the absence of typical signs and symptoms
of infection and mimicry by various noninfectious causes. The pathogens associated
with these infections are often commonly found pathogens of low virulence in immunocompetent
hosts and include various bacteria, parasites, fungi, or viruses. These infections
can present as various clinical syndromes, including meningitis, encephalitis, space-occupying
lesions, stroke-like presentations, or even neoplastic manifestations. Progressive
multifocal leukoencephalopathy can be seen in patients with multiple sclerosis on
various new immunomodulatory drugs in addition to patients with human immunodeficiency
virus, transplantation, or hematologic malignancies, and is characterized by multifocal
white matter lesions. Human herpesvirus-6 causes severe encephalitis in transplant
recipients, known as posttransplantation acute limbic encephalitis. Neoplastic manifestations
like Epstein–Barr virus-associated primary central nervous system lymphoma and posttransplantation
lymphoproliferative disorders are particularly challenging to diagnose and manage.
Modern diagnostic techniques, including advanced imaging techniques like magnetic
resonance spectroscopy, use of polymerase chain reaction, and metagenomic sequencing,
can be helpful in early recognition of pathogens. Treatment of most of these involves
lowering of immunosuppression when possible and use of specific antimicrobial agents
when available. Improved outcomes can be seen when early diagnosis is made.
Keywords
CNS opportunistic infections - posttransplant - progressive multifocal leukoencephalopathy
- EBV
