The role of serum and cerebrospinal fluid cytokines in diagnosis and management of pure neuritic leprosy

BACKGROUND: Pure neuritic leprosy (PNL) lacks skin lesions, making diagnosis difficult. This study evaluated nerve histopathology, immunohistochemistry, serum and cerebrospinal fluid (CSF) cytokines in PNL diagnosis and management. METHODS: In this prospective single-centre observational study conducted over 3 years, patients with mononeuropathy or mononeuropathy multiplex were screened. Diagnosis of PNL was based on clinical, electrophysiological, and nerve biopsy findings. Histopathology, immunohistochemistry, and immunofluorescence were performed. Serum and CSF levels of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), interleukin-6, interleukin-10 (IL-10), and interleukin-1β were measured at baseline and after 3 months of therapy. RESULTS: Among 83 screened patients, 45 were diagnosed with PNL. Most patients were male (84.44%) with a mean age of 44.98±15.03 years. Mononeuritis multiplex was observed in 44.44%. Post-treatment at 3 months reductions in serum and CSF IFN-γ and IL-10 were observed. CSF IFN-γ (p = .008) and IL-10 (p = .04) correlated significantly with clinical improvement. TNF-α negatively correlated with bacillary index (r = -0.448, p = .048), whereas IFN-γ showed a positive correlation (r = 0.673, p = .001). CONCLUSION: Elevated serum and CSF cytokine levels in pure neuritic leprosy decline after therapy, highlighting their potential role in diagnosis and treatment monitoring. Cytokine profiling with immunohistochemistry may support early diagnosis and treatment monitoring in pure neuritic leprosy.