Autoimmune enteropathy (AIE) is a rare disorder of the immune system that affects infants, young children and (rarely) adults causing severe diarrhea, vomiting, and other morbidities of the digestive tract. AIE causes malabsorption of food, vitamins, and minerals often necessitating replacement fluids and total parenteral nutrition. Some disorders, such as IPEX syndrome, include autoimmune enteropathy as well as autoimmune "pathies" of the skin,  thyroid,  other glands, or kidneys. Symptoms
The main symptoms of AIE include:

Diarrhea (frequent loss of fluids)
Intestinal inflammation
Vomiting
Intestinal bleeding
Difficulty or inability to gain weight
Rapid weight loss
Decreased urine output from dehydration

Diagnosis
There is a diagnostic test for AIE that looks for an antibody against the enterocyte. The diagnostic test contains the Western Blot which can identify the antibody IgG or IgA and with the immunohistochemistry can localize these antibodies. Endoscopy with biopsies of the colon, small colon, stomach, and other locations may be helpful in diagnosing. This test is done to look at the stomach and small intestines and to see what cells are infiltrating the digestive tract. There are also documented cases of autoimmune enteropathy where the auto-antibodies were undetectable and the diagnosis was made on the basis of clinical presentation and response to treatment. Types
There are 3 types of autoimmune enteropathy:Type 1: IPEX syndrome: Immune dysregulation, Polyendocrinopathy, Enteropathy, X – linked 
	syndrome, which is caused by a mutation in the FOXP3 gene. This can only affect boys. Type 2: IPEX-like, which manifests similarly to IPEX syndrome but without recognizable mutations in the FOXP3 gene.
Cold autoimmune hemolytic anemia caused by cold-reacting antibodies. Autoantibodies that bind to the erythrocyte membrane leading to premature erythrocyte destruction (hemolysis) characterize autoimmune hemolytic anemia. Presentation
A common complaint among patients with cold agglutinin disease is painful fingers and toes with purplish discoloration associated with cold exposure. In chronic cold agglutinin disease, the patient is more symptomatic during the colder months. Cold agglutinin mediated acrocyanosis differs from Raynaud phenomenon. In Raynaud phenomena, caused by vasospasm, a triphasic color change occurs, from white to blue to red, based on vasculature response. No evidence of such a response exists in cold agglutinin disease. Other symptoms

Respiratory symptoms: May be present in patients with M pneumoniae infection. Hemoglobinuria (the passage of dark urine that contains hemoglobin), A rare symptom that results from hemolysis, this may be reported following prolonged exposure to cold, hemoglobinuria is more commonly seen in paroxysmal cold hemoglobinuria. Chronic fatigue, Due to anemia. Causes
Cold agglutinins develop in more than 60% of patients with infectious mononucleosis, but hemolytic anemia is rare. Classic chronic cold agglutinin disease is idiopathic, associated with symptoms and signs in relation to cold exposure. Causes of the monoclonal secondary disease include the following:

B-cell neoplasms - Waldenström macroglobulinemia, lymphoma, chronic lymphoid leukemia, myeloma
Non hematologic neoplasmsCauses of polyclonal secondary cold agglutinin disease include the following:

Mycoplasma infections. Viral infections: Infectious mononucleosis due to Epstein-Barr virus (EBV) or CMV, Mumps, varicella, rubella, adenovirus, HIV, influenza, hepatitis C.
Bacterial infections: Legionnaire disease, syphilis, listeriosis and Escherichia coli. Parasitic infections: Malaria and trypanosomiasis.