Diagnosing Balamuthia mandrillaris amebic meningoencephalitis in a 64-year-old woman from the Southwest of China

Abstract

Balamuthia mandrillaris amebic encephalitis (BAE) can cause a fatal condition if diagnosis is delayed or effective treatment is lacking. Patients with BAE have been previously reported in 12 provinces of China, with skin lesions being the primary symptom and encephalitis developing after several years. However, a significantly lower number of cases has been reported in Southwest China. Here we report an aggressive BAE case of a 64-year-old woman farmer with a history of skin lesions on her left hand. She was admitted to our hospital due to symptoms of dizziness, headache, cough, vomiting, and gait instability. She was initially diagnosed with syphilitic meningoencephalitis and received a variety of empirical treatment that failed to improve her symptoms. Finally, she was diagnosed with BAE combined with amebic pneumonia using next-generation sequencing (NGS), qRT-PCR, sequence analysis, and imaging studies. She died approximately 3 weeks after the onset. This case highlights that the rapid development of encephalitis can be a prominent clinical manifestation of Balamuthia mandrillaris infection.

Keywords: Balamuthia mandrillaris; Southwest China; amebic encephalitis; amebic pneumonia.

Fig. 1

Imageological features of a patient with Balamuthia mandrillaris disease. Computed tomography (CT) of the brain (A, B, and C) and the lung (D, E, and F) were performed on days 1, 9, and 13, respectively; magnetic resonance imaging (MRI) of the brain was initially performed on day 3 (G–J) and again on day 8 (K–N).

Fig. 2

Identification of B. mandrillaris in the patient’s cerebrospinal fluid. (A) The presence of B. mandrillaris genomic DNA in the CSF sample was detected using next-generation sequencing (NGS), (B) sequencing coverage and depth, (C) TaqMan qRT-PCR targeting the RNase P gene, and (D) PCR amplification targeting of the 16S RNA gene (D). A: The mapped read number was distributed across the genomic region of B. mandrillaris. B: Whole genome of B. mandrillaris was divided into 500 equal parts, i.e., 500 window bins, and the coverage and depth of each bin were then calculated. Coverage represents the percentage covered by reads. Depth represents the average depth in the bin region. C: The CSF was 10-fold serially diluted, and qRT-PCR targeting the B. mandrillaris RNase P gene was performed using the primer set RNP-F, RNP-R, and TaqMan RNP probe. D: B. mandrillaris DNA was also amplified using primer sets, namely Balspec16S/Balspec16SR (lane 1, 395 bp), BalaF1451/BalaR1621 (lane 2, 336 bp), and Balspec16S/Balspec16SR2 (lane 3, 1, 240 bp). The PCR products were sequenced after T-A cloning.

Fig. 3

Microscopic image of B. mandrillaris in the patient’s cerebrospinal fluid. (A) Spherical cysts, measuring 15–20 μm in size; (B) Ovoid to round trophozoites, measuring 20–25 μm in size, and 1–2 nuclei containing 1–4 nucleoli were noted (Original magnification×40. The scale is 20 μm).