<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by beta-mannosidosis ? [/INST] Beta-mannosidosis is believed to be a very rare disorder. Approximately 20 affected individuals have been reported worldwide. It is difficult to determine the specific incidence of beta-mannosidosis, because people with mild or non-specific symptoms may never be diagnosed. </s>