Anemia can be caused by any disease that adversely affects the bone marrow or the blood components. These include: infectious diseases: Rickettsia diseases such as Anaplasmosis or Ehrlichia; bacterial infections, such as Hemobartonella, or Leptospirosis; protozoal diseases such as blood parasites like Babesia and others; viral disease; chemotherapy agents; toxins; internal blood loss such as bleeding ulcers or bleeding tumors; or external blood loss, traumatic wounds; kidney disease (decreased erythropoietin production-hormone aiding in blood manufacture); auto-immune hemolytic anemia diseases; Hormonal diseases such as Addison's, Cushings or Hypothyroid disease; nutrient deficiencies (iron or vitamin B12), and many more.
Chronic or mild prolonged anemia can occur as a secondary component to a wide variety of other diseases.
It sounds as if your friends dog may have chronic anemia, which can appear as vague signs of lethargy, weakness, and anorexia, and weight loss. Unfortunately this can be a diagnostic dilemma, since it has so many causes. Tick borne disease and auto-immune diseases should be ruled out with blood work and biopsy of the lesions around the nose and of some of the skin lesions. Besides tick borne disease lupus or pemphigus (auto-immune diseases) are a possibility. Hypothyroid and Cushings, and Addison's disease can account for symptoms such as: skin conditions, hair loss (especially if symmetrical) and mild anemia.
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