My daughter is a twin – age 12. They are fraternal. Only one has MS (diagnosed at age 11). What's the chance that the other twin will get MS? The neurologist did find it interesting that one month before the double vision started (for the twin with MS) and eventually the MS diagnosis – her period started for the first time; but for the other twin (that doesn't have MS) - her period started a year later.
The risk to fraternal twins of MS patients is higher than the general population, but still rather low (5-15% range depending on the study that is read). It is not clear why some people get MS and not others, but we do have data to suggest that it takes a variety of events happening at the right time. It takes a genetic risk, but then the person has to be exposed to the right trigger. Maintaining adequate vitamin D3 levels have been shown to reduce the risk of MS and would be something all families should consider when one child gets diagnosed with MS.
Benjamin M. Greenberg, MD, MHS
Director, Transverse Myelitis and Neuromyelitis Optica Program
Director, Pediatric Demyelinating Disease Program
Department of Neurology and Neurotherapeutics
Department of Pediatrics
Cain-Denius Scholar of Mobility Disorders
University of Texas Southwestern Medical Center