Final answer:
A copper deficiency is the most likely cause of anemia, neutropenia, and neurological symptoms in a patient with normal B12 and iron levels, especially after gastric bypass surgery.
Step-by-step explanation:
The 51-year-old female patient's symptoms of numbness and tingling in the lower extremities, combined with anemia and neutropenia, despite normal B12, iron, ferritin, and transferrin levels, suggest a potential deficiency in a nutrient not listed in the lab results. Considering her history of gastric bypass surgery, which can impact nutrient absorption, and the provided options, copper deficiency seems most likely. Copper is essential for the formation of red blood cells and the maintenance of nerve health. A deficiency can lead to symptoms such as anemia, neutropenia, and neurological symptoms like numbness and tingling, as seen in this patient.