Lethal outcome of granulomatous acanthamoebic encephalitis in a man who was human immunodeficiency virus-positive: a case report

Background Acanthamoeba species can cause disseminating infections in immunocompromised individuals. Case presentation Here, we report a case of granulomatous acanthamoebic encephalitis with a lethal outcome in a 54-year-old German man who was human immunodeficiency virus-positive. The diagnosis was based on symptoms of progressive neurological deficits, including sensorimotor paralysis of his right leg and deteriorating alertness. Due to the rapid course and rather late diagnosis of the infection, effective treatment could not be applied and he died 12 days after hospital admission. Conclusions To the best of our knowledge, this is the second case of granulomatous acanthamoebic encephalitis reported within Germany. Our case highlights the importance of early diagnosis of granulomatous acanthamoebic encephalitis to prevent fatal outcome.


Background
Acanthamoeba species are free-living amoeboid single-cell organisms that naturally occur in water and soil, but can also be found in human-made habitats all over the world [1][2][3][4][5]. Acanthamoeba species are known as causal agents of disseminating infections in immunocompromised individuals (for example, human immunodeficiency virus (HIV) positive, immunosuppressive therapy), including granulomatous acanthamoebic encephalitis (GAE) [6][7][8]. GAE is a rare but mostly fatal disease [6,9]. Furthermore, Acanthamoeba species can cause so-called Acanthamoeba keratitis; Acanthamoeba keratitis mainly occurs in contact lens wearers and increasing casualties have been reported in the past decades [10,11].

Case presentation
In December 2010, a 54-year-old German man presented to our hospital with suspected cerebral toxoplasmosis. HIV infection had been diagnosed in 1995. He had received a triple-combination highly active antiretroviral therapy (HAART) of lopinavir, lamivudine, and tenofovir, which was stopped in 2009 due to intolerable side effects (diarrhea, nausea).
Over a period of 5 days, progressive neurological deficits including sensorimotor paresis of his right leg and deterioration of alertness occurred.
On clinical and neurological examination, he showed high-grade flaccid paralysis of his right lower limb with preserved muscle proprioceptive reflexes and positive Babinski sign.
Magnetic resonance imaging (MRI) on day 1 revealed a periventricular hyperintense lesion with perifocal edema in the left parieto-occipital region which continued to progress as shown in imaging on day 6 ( Fig. 1).
Due to pathologic MRI findings, a stereotactic biopsy was performed on day 9. Histopathological results obtained on day 12 showed extensive tissue necrosis with mixed inflammatory infiltrates. Cysts of Acanthamoeba species were detected in periodic acid-Schiff (PAS) and Grocott stainings of brain specimens. Mononuclear trophozoites could be identified in hematoxylin and eosin (HE) and PAS stainings (Fig. 2). Furthermore, additional immunohistochemical staining was performed using an antibody specific to Acanthamoeba species (from rabbits immunized with Acanthamoeba genotype 4; Fig. 3).
Electroencephalography (EEG) on day 6 showed a lesion located in his left frontotemporal region with epileptic patterns in the left parietal lobe. He developed relapsing   Due to the unfavorable prognosis, we, in agreement with his relatives, took no further intensive care measures. He died on day 12 after hospital admission.
Since histopathology did not reveal GAE before day 12, a specific treatment against GAE (for example, miltefosine-based combination therapy) had not been initiated.

Discussion and conclusions
Infections with Acanthamoeba species are rare; hence, clinicians, pathologists, and clinical microbiologists are generally unfamiliar with these diseases. The vast majority of cases of GAE reported in the literature have been diagnosed postmortem [12,13]. To the best of our knowledge, this is the second case of GAE reported within Germany.
The current case emphasizes the importance of early diagnosis of GAE. Microscopy of centrifuged fresh cerebrospinal fluid is recommended to diagnose Acanthamoeba trophozoites, yet these may be misdiagnosed as macrophages. Histological staining enables a clear differentiation of trophozoites from other cells [13]. Today, PCR is the method of choice for rapid, specific, and sensitive detection of Acanthamoeba species in clinical samples and also allows genotype identification [14] as well as diagnosis from formaldehyde-fixed samples [15,16]. Early diagnosis and specific treatment is only possible if an infection with Acanthamoeba species is suspected early [13].
Today, there is no standard regimen for the treatment of GAE, but several successfully treated cases have been reported. For example: a patient with acquired immunodeficiency syndrome (AIDS) was treated with a combination of fluconazole and sulfadiazine [17]; two immunocompetent children received trimethoprim-sulfamethoxazole, rifampicin, and ketoconazole [18]; another immunocompetent woman was treated with fluconazole, rifampicin, and metronidazole [13]; a young immunocompromised man with underlying tuberculosis was treated with miltefosine, amikacin, and tuberculostatic drugs [8]; and, another young immunocompetent man was treated with rifampicin, moxifloxacin, and fluconazole [19]. The Centers for Disease Control and Prevention (CDC) recommends administration of miltefosine based on 26 reported cases in which a miltefosine-including regimen seemed to offer a survival advantage [20].
Our patient was prophylactically treated with antibiotics, covering antifungal, antiviral, antibacterial, and antiprotozoal activity. He did not receive a miltefosine-based combination therapy. As pointed out earlier, most reported cases of GAE have been diagnosed postmortem [12] and all successfully treated cases were detected early and mainly by chance. Therefore, both awareness and an early and specific diagnosis followed by an immediate start of a miltefosine-based treatment seem of crucial importance for the successful treatment of GAE. Acanthamoeba species should be considered in patients with unclear encephalitis, particularly in immunocompromised patients. Availability of data and materials All data (pictures) generated or analyzed during this study are included in this published article.
Authors' contributions SG treated the patient, collected the data, and wrote the manuscript. JW performed histological staining and took Multichannel pictures. FP provided PAS-stained and HE-stained pictures. SS treated the patient and contributed with analysis and interpretation of data. FE made substantial contributions to the interpretation of data and manuscript review. All authors read and approved the final manuscript.
Ethics approval and consent to participate No ethics approval, but patient's relatives consented (see below).

Consent for publication
Written informed consent was obtained from the patient's next of kin for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

Competing interests
The authors declare that they have no competing interests.