Factors likely to affect the development of multiple sclerosis in patients presenting with optic neuritis in a tropical and subtropical area.

The relationship between optic neuritis (ON) and multiple sclerosis (MS) in a subtropical climate is examined. 105 cases of ON were followed for varying periods over 26 years. The factors studied included place of birth, sex, age at onset, presence of recurrent ON, the interval to the onset of MS, and HLA antigen typing. 55% of cases developed evidence of definite MS. The majority of cases who went on to develop MS had their onset of ON between 21 and 40 years of age. The subtropical climate did not cause any significant variation in incidence. However those case who had HLA Bw4 appear to be protected from developing MS.