On 24 January 2022, a 37-year-old male office clerk presented to our hospital for investigation and management of muscle pain in the extremities with headache. The man used to be in good health and did not have the habits of smoking and alcohol. Five months prior to his admission, he began suffering from symmetry pain in the muscles of the limbs, accompanied by headache on the left side, without nausea, vomiting, or fever. Physical examination revealed body temperature of 36.4 C, heart rate of 76 beats per minute, and blood pressure of 117/69 mm Hg; marked tenderness in gastrocnemius, quadriceps and biceps brachialis. Cardiovascular, abdominal, and neurological examination was unremarkable except for weakness and stiffness in the extremities.
Blood chemistry tests revealed myositis marked by lactate dehydrogenase (LDH) of 695 U/L (normal range, 120-450 U/L), creatine kinase (CK) of 1955 U/L (normal range, 50-310 U/L), creatine kinase-MB (CK-MB) of 438 U/L (normal range, 0-24 U/L), myoglobin (MYO) of 900 U/L (normal range, 23-112 U/L). Preliminary etiological investigations excluded the presence of necrotizing autoimmune myopathy, cryptococcosis, tuberculosis, and toxoplasmosis, but Human immunodeficiency virus (HIV) RNA was positive (2.55x106 copies/muL). Subsequent flow cytometry showed the CD4+ T cell count is 6 cells/microL.
Cerebral magnetic resonance imaging (MRI) revealed multiple parenchymal lesions with fine contrast enhancement in bilateral cerebral hemispheres, pons, medulla oblongata, and right cerebellar hemispheres, most of which are located in bilateral cerebral cortex (the large one can reach 15 mm in diameter) ( Figures 1A-D ). The MRI results suggested infectious lesions. A biopsy of right gastrocnemius was performed, and pathology showed infiltration of lymphocytes and neutrophils. Several scattered oval-shaped pathogens were observed by Gomori methenamine silver staining ( Figure 1E ) and fungal fluorescence staining ( Figure 1F ). To determine the a etiological agents, the gastrocnemius tissue and cerebrospinal fluid were subjected to metagenomic next generation sequencing (mNGS), respectively. Within 24 hours after receipt of the samples, 3 species of fungi, 6 species of bacteria, and 1 species of virus were detected in the gastrocnemius tissue ( Figure 1G ). Meanwhile, 1 species of fungi and 3 species of viruses were detected in cerebrospinal fluid sample ( Figure 1H ). Among these microbes, only T. hominis has been reported to cause myositis in immunocompromised patients. And T. hominis was identified in both gastrocnemius tissue and cerebrospinal fluid. Finally, the diagnosis of myositis and brain infection caused by the infection of T. hominis was made.
During the hospitalization, he received tramadol to relieve his pain. After the T. hominis infection was confirmed, he initiated a 12-week course of oral albendazole (800 mg/d), a 5-day course of oral dexamethasone (5 mg/d), and regular antiretroviral therapy (Biktarvy). The patient was discharged after 6 weeks of treatment, when the myalgia was significantly relived, and the size and degree of brain lesions were improved ( Figure S1 ). Upon follow-up in 2 weeks, the muscle pain and headache were completely recovered. After the 12-week course of treatment, mNGS showed that his cerebrospinal fluid was negative for T. Hominis ( Figure 2 ).