An elderly man with generalized weakness
Submitted by:
Shobhna Singh, MD MPH
Assistant Professor
Hospital Medicine
Department of Medicine
Edited by:
Dhaval Desai, MD
Assistant Professor
Hospital Medicine
Department of Medicine
STORY AND CASE
A 82-year-old man was admitted for evaluation of progressive generalized weakness for a few weeks. Past medical history consisted of dilated cardiomyopathy with LVEF (Left Ventricular Ejection Fraction) of 40%, ventricular tachycardia status-post automatic implantable cardioverter defibrillator (AICD), remote history of large B-cell lymphoma, chronic headache, and dizziness for years which had gotten worse over the past three to four months.
The patient’s initial presentation was notable for a low-grade temperature of 37.6 and borderline hypotension. Physical exam was notable for a pale, chronically ill-appearing man with diffuse weakness. The remainder of the exam, including a neurological evaluation, was unremarkable. Upon further questioning, the patient revealed he was recently placed and then taken off sacubitril/valsartan due to episodes of hypotension. Thereafter, the patient stopped taking his remaining anti-hypertensives. The patient’s initial infectious work up, CT head, echocardiogram, and ICD interrogation were unrevealing. He remained afebrile for the next few days. After IV hydration, he clinically improved. However, on the fourth day of hospitalization, he developed acute altered mental status with associated right facial droop, expressive aphasia, fever, and worsening leukocytosis. A repeat CT head was again negative. Brain MRI showed a left frontal lobe mass suggestive of possible low-grade glioma. The brain lesion was inaccessible for biopsy due to its diffuse nature. Patient was started on dexamethasone and antibiotics to cover meningitis. Lumbar puncture revealed normal glucose, elevated protein, and a cell count of 455 with lymphocytic predominance. Unfortunately, the patient deteriorated after lumbar-puncture and had a witnessed seizure. He was transferred to ICU and emergently intubated for altered mental status due to seizures and meningoencephalitis. Repeat MRI showed severe interval progression of large left frontal lobe lesion, significant mass effect, midline shift, and evidence of herniation. EEG showed no epileptiform activity. Cerebro-Spinal Fluid (CSF) flow-cytometry and CSF serologies were negative. Eventually, the patient’s condition declined rapidly, and his family decided to withdraw all life-supportive therapy.
ANSWER AND EXPLANATION
The patient’s brain autopsy revealed a diffusely abnormal appearing left hemisphere which included a red-purple mass lesion spanning the left frontal-temporal-parietal lobes. Thecut surface exhibited diffluent parenchyma and focal liquefaction. Final pathology showed Acanthamoeba species confirming diagnosis of Granulomatous Amoebic Encephalitis (GAE).
FINAL DIAGNOSIS
Granulomatous Amoebic Encephalitis (GAE)
DISCUSSION
Granulomatous Amoebic Encephalitis (GAE) is a life-threatening infection of the central nervous system caused by free-living amoebae Acanthamoeba spp., Balamuthia mandrillaris, and Sappinia pedata. Common habitats for acanthamoeba species include lakes, swimming pools, tap water, and heating and air conditioning systems. The disease has a subacute to chronic onset and primarily affects immunocompromised people, with a high fatality rate. Its symptoms are nonspecific and progressively worsen over weeks to months. These symptoms can range from nausea, vomiting, low grade fever, and headache to focal motor deficits, seizures, or coma. This makes timely detection challenging. Biopsy is critical and essential to establish the diagnosis and initiate appropriate medical therapy promptly.
Currently, there is no standard therapeutic treatment for GAE. Consultation with the Centers for Disease Control and Prevention (CDC) is advised in all cases. Multiple (typically >5) antiparasitic medicines, including miltefosine, are used in combination. Despite the modest number of patients treated with miltefosine-containing regimens, miltefosine appears to offer a survival advantage and is therefore advised. Miltefosine has been used with pentamidine, sulfadiazine or trimethoprim/sulfamethoxazole, flucytosine, an azole (fluconazole, itraconazole, or voriconazole), rifampin, and amphotericin B to treat Acanthamoeba encephalitis. Skin and disseminated infections produced by Acanthamoeba species or B. mandrillaris are often treated with the same medications, in addition to surgical excision of cutaneous lesions.
This case of GAE represents a rare case of encephalitis caused by a ubiquitous free-living amoeba. As the population ages and the number of immunosuppressed patients rises, GAE cases may increase. To drive positive outcomes, it will be critical for clinicians to maintain a high index of suspicion and consider GAE in the differential diagnosis of patients with central nervous system symptoms and brain abscesses.
CITATIONS
https://rarediseases.info.nih.gov/diseases/12651/granulomatous-amebic-encephalitis
https://pubmed.ncbi.nlm.nih.gov/8017178/
https://pubmed.ncbi.nlm.nih.gov/9225325/
https://pubmed.ncbi.nlm.nih.gov/15956445/
https://pubmed.ncbi.nlm.nih.gov/21697972/
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