The percentage of Taiwanese who develop multiple sclerosis (MS) after an episode of clinically isolated syndrome (CIS) is lower than that reported for other ethnicities, and those who do progress are likely to have a milder disease course, a study found, supporting how factors like geography and genetics may affect this disease.
People with an episode who were underweight, and with brain and spinal cord lesions at the time of CIS were significantly more likely to develop MS than others, its researchers said.
The study, “A prospective, observational study on conversion of clinically isolated syndrome to multiple sclerosis during 4-year period (MS NEO study) in Taiwan,” was published in the journal PLOS ONE.
CIS is defined as the first central nervous system symptom caused by the loss of myelin — the fatty substance the surrounds and protects nerve cells. Some people develop MS after CIS, but the percentages reported by different studies vary considerably, ranging from 30% to 82%.
This range can be affected by a study’s particularly methodology, but it can also be related to the ethnicity, genetic background, and geographical location of the patients.
Researchers assessed the proportion of people with for a single CIS episode within the last two years and enrolled at any of five institutions in Taiwan between November 2008 and November 2014.
In total, 103 people (mean age, 38.6) were followed for four years, and researchers recorded the proportion of those who were later diagnosed with MS or neuromyelitis optica (a nervous disorder that is often misdiagnosed as MS). They also noted the time from the episode until diagnosis, the number of lesions found on an MRI (magnetic resonance imaging) with CIS, and the size of the lesions.
Patients were first evaluated for CIS, and again at a second visit 12 to 16 weeks later. They were then followed by telephone every four months. None were given disease-modifying treatments during follow-up.
Overall, 14.5% of people with CIS converted to MS, and 9.7% developed optic neuritis. The average time from CIS to MS diagnosis was 1.1 years; with half being diagnosed within six months. Over 90% of these patients had mild and slow-progressing disease.
“A low conversion rate to MS in Taiwanese CIS patients, and the majority of them having a mild course and minimal disability suggest the roles of geographic, genetic, and ethnic factors,” the researchers wrote.
Studies in other populations, the researchers noted, had higher rates: 59.5% in a 2015 U.K. study with a four-year followup, 30.5% in a 2016 study in China with a nearly four-year followup, and 28% in a 2016 study in India with an 18-month followup.
The percentage of patients who developed MS was comparable among CIS manifestations, but those with optic neuritis had a slightly lower risk of a later MS diagnosis.
People with a low body mass index (BMI less than 18.5) — meaning they were underweight — and with more and larger MRI lesions in the brain and spinal cord were at a higher risk of MS. No relationship was seen between age or gender and MS diagnosis.
“Below normal BMI and ‘number of demyelinating lesions (four or more)’ are significant predictors of conversion from CIS to MS,” the researchers wrote.
They added that future studies, with more patients and longer follow-up times, are needed to confirm their findings.