A 38-year-old man, who had no history of the disease, was admitted to the Department of Infectious Diseases due to repeated fever, headache, and scattered rashes on his limbs. The fever persisted 13 days before the hospital visit, his highest axillary temperature was 38.5C, and this was accompanied by fatigue and headache. Routine blood examination at our hospital suggested the fever was due to infection, and he was put on ceftriaxone treatment for 1 week. However, the fever did not resolve, and scattered red rashes were seen on his limbs 7 days ago. The rashes subsided after self-administration of anti-allergic drugs. The headache worsened 1 day after the treatment, and this was accompanied by a slow response, thus he was admitted. He was healthy and had no history of bad habits such as drug abuse, having multiple sexual partners, and homosexual practice. The patient's vital signs were as follows: 125/78 mmHg brachial artery blood pressure, 38 C axillary temperature, 84 bpm heart rate, and 22 bpm respiration rate. Additionally, the patient exhibited consciousness, slow reaction, negative neck resistance, pharyngeal hyperemia, no swelling of the tonsils, and no cardiac, pulmonary, or abdominal abnormalities. He did, however, have a few scattered rashes on his extremities, with no evidence of superficial lymph node swelling, normal muscle strength in his extremities, and negative nerve localization signs. A routine blood examination performed one day before admission, revealed a total white blood cell count of 10.89x10^9/L, a neutrophil percentage of 37.6%, a lymphocyte count of 6.22x10^9/L, as well as C-reactive protein (CRP) and Procalcitonin (PCT) levels of 0.93 mg/l and 0.13 ng/mL, respectively. Results from liver function analysis revealed an alanine aminotransferase (ALT) of 148 U/L and aspartate aminotransferase (AST) of 106 U/L. The antigen/antibody test for the human immunodeficiency virus was negative, while Chest CT showed no abnormalities.
Following hospitalization, routine blood tests revealed a total white blood cell count of 10.84x10^9/L, reduced neutrophil percentage (35.4%), an increased lymphocyte percentage (57.2%), a lymphocyte count of 6.20x10^9/L, a monocyte count of 0.69x10^9/L, a CRP of 1.54 mg/ L and PCT: 0.1 ng/ mL (Figure 1). The blood gas analysis indicated normal results, but the liver function test revealed ALT and AST levels of 92.4 and 50.3 U/L, respectively. HCMV and EBV antibody assays revealed positive and negative IgG and IgM respectively, but no HCMV or EBV DNA. A lumbar puncture revealed a cerebrospinal fluid pressure of 110 mmH2O, while results from CSF routine tests revealed negative occult-blood test, light yellow, transparent, Pan's test 4+, nucleated cell counts of 380 /ul, neutral 1%, lymphoid 99%. Additionally, his lactate dehydrogenase increased (161 U/L), glucose levels decreased (2.0 mmol/ L), chloride level decreased (117.8 mmol/L), and his protein levels were >6000 mg/ L. Simultaneously, he had normal electrolyte and blood glucose levels, and the CSF smear test for Cryptococcus was negative. Adenosine deaminase activity in the CSF was 6.1 U/L and the electroencephalogram (EEG) was normal. Brain enhanced MRI+DWI scan showed no obvious abnormalities. Similarly, a Color Doppler ultrasound revealed no abnormalities in the lymph nodes in his neck, underarms, or both sides of the groin. Color Doppler ultrasound of the hepatobiliary, pancreas, and spleen revealed no obvious abnormalities.
On the second day of hospitalization, we collected 3 mL of his CSF and sent it to Hangzhou Jieyi Medical Laboratory (Hangzhou, China) for metagenomic next-generation sequencing. On the 4th day, the mNGS report confirmed the presence of 12 human immunodeficiency virus type 1 (HIV-1) sequences (Figure 2), but no other pathogenic microorganisms (including bacteria, viruses, mycobacteria, fungi, and parasites, among others) were detected. On the third day, both the blood tuberculosis T cell spot test (T-SPOT. TB) and the CSF cryptococcal capsule antigen assays were negative. On the fifth day, mycobacterium tuberculosis DNA analysis from CSF revealed negative results, with no evidence of bacterial growth in either the cerebrospinal fluid or blood cultures.
Lumbar puncture and cerebrospinal fluid examination were performed on the 6th, 9th, and 18th day respectively. The results indicated a progressive decrease in nucleated cell count, while sugar, chloride, and protein levels gradually returned to normal (Table 1). Additionally, CSF smears were negative for Cryptococcus. On the 6th day, 2 mL of CSF was collected and analyzed for the presence of HIV RNA qPCR 910 copies/mL, and blood HIV RNA qPCR 1.37x10^5 copies/mL (Figure 3). HIV antigen/antibody tests, performed between the 5th and 10th days, again showed negative results (the fourth generation), whereas a positive result was obtained on the 17th day. On the 18th day, a Western blot (gp120, gp160, gp41, P24) assay confirmed the presence of HIV in the blood (Table 2). On the 6th day, cell counts revealed CD4+ and CD8+ counts of 447 and 600/ul, respectively. On the 10th day, these counts had decreased, as shown by a CD4+ cell count of 293/ul, and a CD8+ cell count of 517/ul.  
On the second day of hospitalization, tuberculous meningitis was considered based on relevant blood and CSF examination results. Consequently, the patient was administered four diagnostic anti-tuberculosis treatments: isoniazid, rifampicin, moxifloxacin, and linezolid. Additionally, he was administered an intravenous injection with an anti-inflammation dexamethasone needle and symptomatic treatment, which included compound glycyrrhizin for liver protection. On the 6th day, all anti-tuberculosis drugs and dexamethasone needles were discontinued, except for glycyrrhizin (for liver protection) and adequate fluid rehydration. On the second day of hospitalization, the patient's body temperature gradually decreased, before returning to normal. His headache and condition improved, and he was transferred to an outpatient clinic on the 18th day for antiretroviral therapy (ART). His medical history was obtained regarding past protected same-and anal sex activities, 8 days before the onset of symptoms.