Multiple Sclerosis: A Comprehensive Review of Etiology, Immunology, Pathogenesis and Treatment

Abstract

Multiple Sclerosis (MS) is a chronic, immune-mediated inflammatory disease of the Central Nervous System (CNS), characterized by the destruction of the myelin sheath that insulates nerve fibers. This demyelination impairs the transmission of electrical signals, leading to a broad spectrum of neurological deficits. MS primarily affects young adults, with a higher prevalence in women this review focus on etiology ,immunology ,pathogenicity and treatments of MS. The exact cause of MS remains unknown, but it is widely accepted as a multifactorial disease resulting from a complex interplay between genetic Predisposition associations with specific human leukocyte antigen (HLA) alleles, particularly HLA-DRB1*15:01, increase susceptibility, Environmental Triggers: Factors such as low Vitamin D levels, cigarette smoking, and obesity during adolescence are linked to higher risk and Infectious Agents. MS is primarily driven by a breakdown in immune tolerance. Peripheral Activation including autoreactive T-cells (specifically Th1 and Th17) and B-cells are activated in the periphery and migrate across the Blood-Brain Barrier (BBB). Inflammatory cascade inside the CNS, these cells secrete proinflammatory cytokines and recruit macrophages. B-cells contribute via antigen presentation, cytokine production, and the formation of oligoclonal bands (antibodies found in the cerebrospinal fluid). Pathogenesis of MS is the formation of demyelinating plaques within the white and gray matter of the brain and spinal cord. The immune system attacks oligodendrocytes (myelin-producing cells), leading to focal areas of myelin loss while initially considered a disease of myelin, permanent neurological disability is caused by axonal transection and neurodegeneration, which can occur even in early stages. there is currently no cure, management focuses on two pillars including acute relapse management which high-dose corticosteroids (e.g., methylprednisolone) are used to reduce inflammation and accelerate recovery from flare-ups and Disease-Modifying Therapies (DMTs) ,these target the underlying immune response to reduce relapse frequency and slow disability progression.