AIDS Presenting as Granulomatous Amebic Encephalitis: PET and MR Imaging correlation

Acanthamoeba castellanii encephalitis in a patient with AIDS: a case report and literature review

Amoebic encephalitis is a rare cause of CNS infection for which mortality exceeds 90%. We present the case of a 27-year-old man with AIDS who presented to a hospital in Atlanta (Georgia, USA) with tonic-clonic seizures and headache. His clinical condition deteriorated over several days. Brain biopsy revealed lymphohistiocytic inflammation and necrosis with trophozoites and encysted forms of amoebae. Immunohistochemical and PCR testing confirmed Acanthamoeba castellanii encephalitis, typically described as granulomatous amoebic encephalitis (GAE). No proven therapy for GAE is available, although both surgical and multiagent antimicrobial treatment strategies are often used. Most recently, these include the antileishmanial agent miltefosine. Here we review all cases of GAE due to Acanthamoeba spp in people with HIV/AIDS identified in the literature and reported to the Centers for Disease Control and Prevention. We describe this case as a reminder to the clinician to consider protozoal infections, especially free-living amoeba, in the immunocompromised host with a CNS infection refractory to traditional antimicrobial therapy.

Granulomatous amoebic encephalitis caused by Acanthamoeba in a patient with AIDS: a challenging diagnosis

INTRODUCTION

Acanthamoeba spp. is a ubiquitous free-living amoeba that causes human infections affecting predominantly the cornea and central nervous system. The diagnosis and treatment of Acanthamoeba encephalitis is very challenging.

CASE SUMMARY

A 53-year-old male with HIV/AIDS was admitted for altered mental status and fever. On initial examination, he had left hemianopia with left-sided weakness and numbness. MRI revealed an inflammatory and enhancing parenchymal mass associated with leptomeningeal enhancement in the occipitoparietal lobe containing multiple punctate hemorrhages. He was treated with empiric antibiotics for presumptive toxoplasmosis, brain abscess, fungal infection and tuberculosis with an unremarkable lymphoma work up. Initial brain biopsy studies were unremarkable except for non-specific granulomas and adjacent necrotic tissue. The patient passed away 2.5 months after initial presentation with no diagnosis. Post-mortem testing by the Centers for Disease Control and Prevention (CDC) confirmed the diagnosis of granulomatous amoebic encephalitis (GAE) by visualization with immunohistochemistry staining and PCR. Recovery is rare from GAE likely due to delay in diagnosis.

CONCLUSIONS

This case illustrates the importance of including GAE into the differential diagnosis of brain mass. We advocate early molecular testing of tissue specimen by the CDC to achieve an appropriate diagnosis, and a multidisciplinary approach for the management of this condition.

Drug Discovery against Acanthamoeba Infections: Present Knowledge and Unmet Needs

Although major strides have been made in developing and testing various anti-acanthamoebic drugs, recurrent infections, inadequate treatment outcomes, health complications, and side effects associated with the use of currently available drugs necessitate the development of more effective and safe therapeutic regimens. For any new anti-acanthamoebic drugs to be more effective, they must have either superior potency and safety or at least comparable potency and an improved safety profile compared to the existing drugs. The development of the so-called 'next-generation' anti-acanthamoebic agents to address this challenge is an active area of research. Here, we review the current status of anti-acanthamoebic drugs and discuss recent progress in identifying novel pharmacological targets and new approaches, such as drug repurposing, development of small interfering RNA (siRNA)-based therapies and testing natural products and their derivatives. Some of the discussed approaches have the potential to change the therapeutic landscape of Acanthamoeba infections.

Acanthamoeba and its pathogenic role in granulomatous amebic encephalitis

Acanthamoeba is a free-living amoeba that is widely distributed in the environment. It is an opportunist protist, which is known to cause rare yet fatal infection of the central nervous system (CNS), granulomatous amebic encephalitis (GAE) in humans. GAE cases are increasingly been reported among immunocompromised patients, with few cases in immunocompetent hosts. Diagnosis of GAE primarily includes neuroimaging, microscopy, cerebrospinal fluid (CSF) culture, histopathology, serology and molecular techniques. Early diagnosis is vital for proper management of infected patients. Combination therapeutic approach has been tried in various GAE cases reported worldwide. We tried to present a comprehensive review, which summarizes on the epidemiology of GAE caused by Acanthamoeba along with the associated clinical symptoms, risk factors, diagnosis and treatment of GAE among infected patients.