Central nervous system aspergillosis was misdiagnosed as toxoplasma gondii encephalitis in AIDS: a case report

doi:10.21203/rs.3.rs-1557528/v1

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Case Report

Central nervous system aspergillosis was misdiagnosed as toxoplasma gondii encephalitis in AIDS: a case report

https://doi.org/10.21203/rs.3.rs-1557528/v1

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Background: Patients with acquired immunodeficiency syndrome (AIDS) tend to suffer from a complication of several central nervous system (CNS) infections owing to hypoimmunity. However, CNS aspergillosis (CNSAG) is extremely rare and difficult to diagnose, which makes it easily misdiagnosed.

Case presentation: We have reported here a 47-year-old male AIDS patient with visual ghosting and no sweat development on the left head and face. He was accordingly diagnosed with toxoplasma gondii encephalitis (TE) in other hospitals, for which he received regular anti-toxoplasma gondii and anti-human immunodeficiency virus (anti-HIV) treatment. Then, the patient was transferred to our hospital due to lack of any improvement with the prescribed treatment. The patient's neurological examination revealed no abnormalities at admission, albeit only a slight change in the cerebrospinal fluid. His cranial magnetic resonance imaging (MRI) revealed multiple abnormal signals in the brain parenchyma, and his blood sample was positive for toxoplasma gondii IgG antibody. The initial diagnosis at our hospital was also TE. Considering the poor efficacy of anti-TE treatment, cerebrospinal fluid metagenomics next-generation sequencing (mNGS) was performed, but no pathogenic bacteria were detected. However, aspergillus fumigatus was detected in the cerebrospinal fluid with targeted next-generation sequencing (tNGS) and bronchofiberscope alveolar lavage fluid mNGS. The diagnosis was accordingly modified as CNSAG combined with his other clinical manifestations. After administering voriconazole anti-fungal therapy, the patient’s symptoms were relieved, with improved absorption of the intracranial lesions.

Conclusions: The present case experience indicated the need for the clinicians to strengthen their understanding of CNSAG. Moreover, for patients with diagnostic difficulties, early mNGS and tNGS (using biological samples with only a few pathogens) were helpful for the early diagnosis and treatment, whereby the patients could achieve favorable outcomes.

CNSAG

AIDS

mNGS

tNGS

Central nervous system aspergillosis (CNSAG) is a rare disease related to low immunity, with a high incidence rate in patients with solid organ transplantation or hematological diseases as well as in patients undergoing long-term immunosuppressive treatment ^[1]. Owing to the patient’s hypoimmunity, the acquired immunodeficiency syndrome (AIDS) tends to get complicated with various central nervous system (CNS) infections, such as tuberculous meningitis, toxoplasma gondii encephalitis (TE), and cryptococcal meningitis. However, AIDS combined with CNSAG has rarely been reported ^[2–3]. The clinical symptoms of CNSAG are nonspecific and associated with the degree of intracranial involvement, which are often manifested as headache, focal neurological dysfunction, altered mental state, or vasculitis ^[4–5]. Routine examination of the cerebrospinal fluid, biochemical detection, and cranial imaging examination also get limited due to low specificity ^[6]. The diagnosis of CNSAG is mainly based on positive cerebrospinal fluid culture or biopsy to identify the pathogens; however, this process is time-consuming with a low positive rate, making early and accurate diagnosis difficult. A present, the wide application of metagenomics next-generation sequencing (mNGS) technology for extensive and unknown pathogens has dramatically improved the detection rate of etiology. However, mNGS has some limitations for the cerebrospinal fluid with low count of pathogenic bacteria. Targeted next-generation sequencing (tNGS) is a highly sensitive detection technology for known pathogens that can significantly improve the clinical detection rate of pathogens which are difficult to detect and have low copy infections. The tNGS makes up for the deficiency of mNGS and assists early diagnosis and early treatment clinically to improve the patient survival rate. We have reported herein the case of a patient with CNSAG that was misdiagnosed as TE.

The case patient is a 47-year-old, married, male construction worker. The patient was treated at a hospital in Chongqing on May 10, 2021 due to cough, shortness of breath, and other discomfort and was accordingly diagnosed with pneumocystis carinii pneumonia (PCP) and AIDS. The baseline of CD4+ T-cell count and HIV-RNA level were not clear. After anti-PCP treatment (with compound sulfamethoxazole tablets combined with prednisone), his symptoms were relieved, after which antiretroviral therapy (ART), including lamivudine (3TC), tenofovir (TDF), and efavirenz (EFV) were initiated. He took the ART and compound sulfamethoxazole tablets regularly.

He was hospitalized on August 19, 2021 due to visual ghosting since >2 months and no sweat development on the left head and face for the past 20 days. Over 2 months before hospital admission, the patient experienced bilateral visual ghosting and limited rotation of the left eye without any obvious inducement. Moreover, he had no fever, dizziness, headache, tinnitus, decreased hearing and vision, visual rotation, syncope, disturbance of consciousness, nausea, vomiting, incontinence, abdominal pain, diarrhea, and other discomforts. Accordingly, the patient was treated at a hospital in Chongqing. His cranial MRI revealed multiple intracranial abnormal enhancement signals with edema signals. Furthermore, his routine examination of the cerebrospinal fluid and biochemical detection indicated slight abnormalities. He was diagnosed with TE and AIDS. After treatment with azithromycin combined with compound sulfamethoxazole tablets against toxoplasma gondii for 2 weeks, the patient reported slight improvement in his visual ghosting. Then, he was discharged without any imaging re-examination and was continued on the original anti-toxoplasma gondii treatment after the discharge. Then, 20 days before his re-admission (the patient had been receiving continuous anti-toxoplasma gondii treatment until his hospitalization in our hospital), the patient still had no sweat development on the left head and face and his bilaterally visual ghosting due to unknown causes had worsened, accompanied by limited rotation of the left eye, slight cough, and less sputum production. He had no tinnitus, decreased hearing and vision, visual rotation, blackness, epilepsy, disturbance of consciousness, and other discomforts. His brain MRI re-examination in other hospitals indicated that the intracranial lesions had increased significantly, after which the patient was transferred to our hospital for further treatment.

The results of patient’s physical examination on admission are as follows: normal vital signs and a clear mind, and he answered to the point; the bilateral pupils were equal in size and circular-shaped, showing sensitivity to light reflection; the left eye had external rotation disorder, but the right eye had normal activity; his lungs had clear respiratory sound, without rhonchus and moist rales; no abnormality was detected in cardiac and abdominal physical examination; the muscle strength and tension of the limbs were normal; pain and temperature sensation were normal, and bilateral pathological signs were negative. The results of his laboratory examination were as follows: cranial MRI showed patchy mixed long T1 and T2 signals in the bilateral frontal lobes and mixed high signals in Flair, surrounded by massive edema. Enhanced scanning revealed that multiple intracranial lesions were circular, nodal, and enhanced, and the intracranial pia mater was slightly thickened. His chest CT indicated that the lungs were scattered with patchy, strip-shaped, nodule-like, acinar nodular increased shadows with uneven density and some unclear boundaries. His routine blood test results were as follows: white blood cells 3.08 × 10⁹/L, neutrophils 2.29 × 10⁹/L; the pressure of cerebrospinal fluid: 140 mmHg, routine examination of the cerebrospinal fluid revealed a positive result for Pandy’s test. His cerebrospinal fluid biochemistry was as follows: total protein 498.77 mg/L, microalbumin 360.7 mg/L, β2 microglobulin 5.26 mg/L, glucose 3.41 mmol/L, chloride 128.8 mmol/L. The CD4⁺ T-cell count 57 cells/µl, CD8⁺ T-cell count 322 cells/µl, CD4/CD8: 0.18; toxoplasma gondii IgG antibody in the blood: positive, toxoplasma gondii IgM antibody and toxoplasma gondii DNA: negative, galactomannan (GM) test in the blood, (1, 3)-β-D glucan (BG), marneffei antigen, cryptococcus neoformans antigen, latent tuberculosis infection, and cytomegalovirus DNA: negative. The cerebrospinal fluid stained with India ink, cryptococcal antigen, cytomegalovirus DNA, tuberculosis fluorescence staining, tuberculosis sandwich cup, bacterial and fungal culture: all negative. The primary diagnosis was 1. TE? 2. AIDS. The patient continued to receive 3TC/TDF/EFV anti-human immunodeficiency virus (anti-HIV) treatment and azithromycin combined with compound sulfamethoxazole against toxoplasma gondii. After 1 week of the treatment, the issue of visual ghosting and facial anhidrosis did not improve. As per a past report, diagnosis and treatment experience of AIDS complicated with TE have shown significant curative effects after regular treatment for 2-4 weeks [7]. Therefore, we wondered whether TE was erroneously diagnosed. For precise diagnoses, the cerebrospinal fluid was collected for mNGS examination (RDP-seq®, Guangzhou Sagene Biotechnology Co., Ltd.), and the results indicated no possible pathogenic bacteria such as toxoplasma gondii, CMV, and cryptococcus. Then, tNGS examination was performed on the cerebrospinal fluid sampled previously (Guangzhou Sagene Biotechnology Co., Ltd.) and the results indicated aspergillus fumigatus (number of sequences: 1). CNSAG was not diagnosed immediately as the number of t-NGS sequences in the cerebrospinal fluid was extremely low. Considering that aspergillus fumigatus usually invaded the lungs and there were lesions present in the patient's lungs, fiberoptic bronchoscopy was immediately performed. The bronchoalveolar lavage fluid (BALF) was collected for mNGS examination (RDP-seq®, Guangzhou Sagene Biotechnology Co., Ltd.), and the results showed a large number of aspergillus fumigatus (number of sequences: 5842, the degree of confidence: 99%) (Fig. 1).

In addition, the BALF-GM test result was positive. Based on the patient's symptoms, signs, laboratory tests, and past treatment reactions, the diagnosis was corrected to CNSAG, invasive pulmonary aspergillosis (IPA), and AIDS. Voriconazole (intravenous drips of 6 mg/kg/day q12-h on the first day, followed by intravenous drip of 4 mg/kg/day q12-h) was administered for anti-fungal treatment. Due to the interaction between voriconazole and EFV, the anti-viral treatment regimen was revised to 3TC, TDF, and dolutegravir (DTG). After 2 weeks of this treatment, the patient’s visual ghosting and facial anhidrosis relieved. The routine examination of cerebrospinal fluid showed normal biochemistry. His cranial MRI indicated the lesions in the frontal lobe were absorbed, and the surrounding edema was alleviated (Fig. 2). The patient was discharged and continued on oral voriconazole treatment (200 mg/kg/day). After 6 weeks of anti-fungal treatment, the patient's visual ghosting and facial anhidrosis were significantly relieved. The re-examination of his cranial MRI indicate that the lesions in the frontal lobe were significantly absorbed and improved, and the surrounding edema was alleviated (Fig. 2), while his chest CT showed focal absorption (Fig. 3).

Invasive aspergillosis (IA) is a common severe infection in immunosuppressive patients that results in high mortality when IA is not treated in time. Based on the statistics, aspergillus fumigatus is the most common pathogenic bacterium in IA [4]. IA commonly invades the lungs in AIDS patients, but it can spread to the other organs, including CNS, albeit it is less common. When aspergillus invades the CNS, the positive culture rate is low due to the low count of pathogenic bacteria in the cerebrospinal fluid ^[8]. Moreover, brain tissue biopsy is not a universal approach and inaccessible to several medical institutions, which often leads to the misdiagnosis of CNSAG, thereby affecting the optimal anti-infection treatment approach.

The present case patient had a history of AIDS, with a low level of CD4 T-lymphocyte. Neurological symptoms appeared earlier, and the cerebrospinal fluid changes were relatively slight. However, his brain MRI revealed multiple focal lesions in the brain parenchyma, surrounded by edema, while his enhanced MRI revealed circular enhancement, similar to the TE imaging findings reported elsewhere [9]. Toxoplasma gondii IgG in the blood was positive, and TE was one of the most common CNS opportunistic infections of AIDS [10]. The present findings may be crucial to the misdiagnosis of this case as TE by other hospitals and even our hospital. However, after regular treatment for 2-4 weeks, most AIDS patients with TE may show a good curative effect in their clinical symptoms and intracranial imaging results [7]. The present patient showed a relatively poor effect despite regular anti-toxoplasma gondii treatment for >4 weeks. Furthermore this patient had received regularly sulfamethoxazole tablets after released from hospital three month earlier because of PCP, research shows that Toxoplasma gondii encephalopathy is very rare under prevent treatment by Sulfonamides [11]. In this condition we have to keep in mind whether the diagnosis is correct, and need to take a further step to find out true etiology and pathogenesis, such as other pathogen infection or cancer.

The mNGS, which is a novel gene detection technology, can theoretically detect all pathogens in samples rapidly and without any bias, targeting bacteria, viruses, fungi, and parasites, making it especially suitable for rare, emerging, and atypical pathogens [12–14]. According to the expert consensus on the clinical application of Chinese metagenomics second-generation sequencing technology for the detection of infectious pathogens, for severe, critically ill patients or immunosuppression and immune-deficiency patients with clinically suspected infection, it is recommended to collect samples from suspected infected sites for second-generation sequencing along with the conventional laboratory and molecular biology testing. The case patient met the abovementioned requirements, albeit no pathogenic bacteria were detected, which may be attributed to the low bacterial count. Moreover, the sampled cerebrospinal fluid was sent for tNGS examination, a high-throughput sequencing detection technology only for specific known pathogens. When compared with mNGS, tNGS offers higher sensitivity and specificity, making it especially suitable for detecting common, difficult detection, and low copy infectious pathogens in a clinical setting [15]. The results of t-NGS in the cerebrospinal fluid showed aspergillus fumigatus (number of sequences: 1). Due to the low number of t-NGS sequences in the cerebrospinal fluid, CNSAG was not diagnosed immediately. Nonetheless, IA seemed a probable diagnoses.

Past studies have shown that serological diagnostic methods are of great significance for the diagnosis of IA [16]. GM and BG are two important antigens, of which GM antigen can be expressed in the early infection of IA[17]. Unfortunately, BG and GM in the present patient’s serum were negative, which failed to provide any evidence for invasive fungal infection. HIV infection is an independent risk factor for IA [17]. Moreover, 3 months before hospitalization, the patient received prednisone treatment for severe PCP and glucocorticoid treatment could inhibit the function of macrophages, which may be another risk factor for IA [18].

As previously mentioned, aspergillus fumigatus usually invades the lungs. Although the chest CT of the patient did not reveal any halo sign, air crescent sign, or other typical signs, he reported respiratory symptoms such as cough and expectoration, with multi-morphological lesions on chest CT. In addition, no reasonable pathogen seemed suspicious to cause the patient's intracranial infection. Then, the patient underwent fiberoptic bronchoscopy examination and BALF was collected for mNGS detection. The results revealed a large number of aspergillus fumigatus (number of sequences: 5842, the degree of confidence: 99%). Meanwhile, the results of BALF-GM test were positive, which also indicated IA infection. The patient was accordingly diagnosed with CNSAG and IPA based on his symptoms, signs, laboratory examination, and past treatment response. Early diagnosis of CNSAG is thus essential for successful treatment. Therefore, for CNS infection patients, if could not find any pathogen which caused infection through normal molecular test, mNGS should be performed as early as possible. For pathogens with clinically difficult detection and low copy infection, tNGS detection can be considered meanwhile or subsequently. In addition, as an auxiliary technology for clinical pathogen diagnoses, the detection results of tNGS are affected by several factors, including the sample quality, pathogen content, detection technology, and method of analysis. Thus, the number of sequences cannot be used as the standard for clinical diagnosis. We thus need to determine the diagnostic basis through comprehensive analysis combined with deep exploration in the future clinical practice.

Voriconazole is the first-line treatment for aspergillus [19], and it passes through the blood-brain barrier. Therefore, the patient was administered voriconazole anti-fungal treatment. After 6 weeks of this treatment, the patient's visual ghosting and facial anhidrosis symptoms show complete relief. Reexamination of the cranial MRI and chest CT showed that the lesions were absorbed and had improved. Notably, several core drugs used in the anti-viral treatment of AIDS are metabolized by liver cytochrome P450 isozyme, which then has a serious drug interaction with voriconazole that is metabolized by the same metabolic pathway. Hence, clinicians should remain vigilant when formulating anti-viral treatment regimens to avoid affecting the efficacy of anti-HIV and anti-fungal therapy.

In this case, it is worth noting that the healthy population also expresses toxoplasma gondii IgG antibody, with positive rate reaching 7.9% [20]. This index, however, only indicates that the patient has been infected with toxoplasma gondii before and cannot be used as a diagnostic index of TE. In addition, the clinical manifestations, routine examination of the cerebrospinal fluid, and the biochemical detection of CNSAG lack specificity, and some of its imaging manifestations are similar to those of TE. Therefore, one should remain vigilant to avoid such serious misdiagnosis. Finally, for AIDS patients with clinically suspected infection, it is recommended to perform mNGS as early as possible followed by further tNGS, if deemed necessary In addition, for accurate diagnosis, brain biopsy should test if needed, because imaging between CNSAG and intracranial tumor have some similarity.

AIDS: acquired immunodeficiency syndrome, CNS: central nervous system, CNSAG: central nervous system aspergillosis, HIV: human immunodeficiency virus, TE: toxoplasma gondii encephalitis, mNGS: metagenomics next-generation sequencing, tNGS: targeted next-generation sequencing, tNGS: IPA: invasive pulmonary aspergillosis, PCP: pneumocystis carinii pneumonia, ART: antiretroviral therapy ART, GM: galactomannan, BG: (1, 3) -β-D-glucan.

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Written informed consent was obtained from the patient for publication of this case report and the accompanying images.

Authors’ contributions

HY is the first author who contributed to the writing of the paper and performed the analysis. ML is the author for correspondence and contributed to the study design, analysis, data collection, and writing of the paper. XH and JN contributed to the design and analysis as well as the article review. SG provided technical assistance. YC contributed to the data review and manuscript revision. All authors read and approved the final manuscript.

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Central nervous system aspergillosis was misdiagnosed as toxoplasma gondii encephalitis in AIDS: a case report

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2. Case Report

3. Discussion

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