A 13 year old white female the daughter of norwegian

Question

This case study:

A 13 year old white female, the daughter of Norwegian immigrants, complains of diarrhea and flatulence. 

HPI Her parents say she has suffered from weight loss despite the fact that she eats very well. Her mother adds that her stool is foul-smelling and floats but no blood or mucus.

PE Patient pale and thin; dryness and thickness of skin; rash on knees, elbows, and neck; itchiness and redness and some scaling of the skin.

Labs CBC: macrocytic, hypochromic anemia, K ⁺ = 3.1 mEq/L (normal 3.6-5.2 mEq/L). 

Three questions:

1. What is the Diagnosis? 
2. What is the Etiology of Macrocytic anemia?
3. What is the Etiology of Hypokalemia?