Expert answer:
Usually the order of things is a bit different: gastritis can cause vitamin B12 deficiency which in turn causes megaloblastic anemia and muscle weakness in the legs may be just a secondary symptom.
Patient with muscle weakness in the legs and with autotrophic gastritis and megaloblastic anemia. Vitamin B deficiency can cause all of this ...
Usually the order of things is a bit different: gastritis can cause vitamin B12 deficiency which in turn causes megaloblastic anemia and muscle weakness in the legs may be just a secondary symptom.