Multiple sclerosis (MS) is a chronic autoimmune disease characterized by demyelination and neurodegeneration in the central nervous system (CNS). The pathogenesis of MS is complex and incompletely understood. It is an autoimmune disease with combination of both genetic and environmental risk factors. Understanding the immune-mediated mechanisms and the influence of genetic and environmental risk factors may help to further improve therapeutic approaches and prevent disease progression. T regulatory cell expressing the CD4, CD25, and forkhead box P3 (FoxP3)markers is the regulatory subtype of CD4+ T cells , Immunologically Treg cell has the main role in secreting the transforming growth factor‐beta (TGF‐β) and IL‐10 cytokines, regulating the immune responses against infectious or cancers, suppressing the auto-reactive T cells, and maintaining the immunologic self‐tolerance ,The Treg cell dysfunction in MS, followed by breaking down of self‐tolerance, led to autoreactive T‐cell suppression failure, myelin and neural destruction, then neuroinflammation. Inflammatory lesions of the spinal cord usually appear as acute partial transverse myelitis (APTM) with rapid onset and tend to show asymmetric neurological signs. APTM may be the first manifestation of MS, it also may remain the only neurological effect during life or recur as relapsing myelitis. The possibility of developing MS was shown to be higher after APTM than after optic neuritis. In 2001, Ian McDonald developed a new criteria for diagnosing MS, which is now known as the ‘‘McDonald criteria’’ That replaced the Poser criteria and started the use of MRI as a central tool in the diagnosis of multiple sclerosis. It demanded evidence of dissemination of lesions in both space and time which could be proved clinically or by MRI reinforced by other paraclinical diagnostic methods like cerebrospinal fluid examination to enable the diagnosis of multiple sclerosis in patients with different clinical presentations. In the 2017 revised McDonald criteria is oligoclonal bands was taken as a substitute for DIT, therefore, can be used to start the diagnosis of multiple sclerosis after the first clinical event and a single brain MRI.