A 35 year woman gives a CBC and serum sample in pathology department of laboratory. His clinical finding shows low Hb and decrease in vitamin B12 and folate deficiency. What could be the associated...

A 35 year woman gives a CBC and serum sample in pathology department of laboratory. His clinical finding shows low Hb and decrease in vitamin B12 and folate deficiency. What could be the associated disease? Explain how can deficiency of these factor cause disease and their role?