5.1 Consequences of iron deficiency
We find a 50-year-old woman with long-term Crohn’s disease, on various treatments and with an abdominal surgical history. Her blood tests were requested following a routine GP visit, when she complained of some lethargy, fever and diarrhoea.
- The results outside the reference range are haemoglobin, MCV and ESR. This result, along with the history, is sufficient to confer the diagnosis of anaemia. With the MCV below the bottom of the reference range, we can extend the diagnosis to microcytic anaemia. The abnormal ESR adds little to the diagnosis as it is the likely consequence of the anaemia.
- Having given the patient a diagnosis, a treatment must be initiated. However, this is not yet possible as the basis of the microcytic anaemia must be defined. As the two major causes of microcytic anaemia are iron deficiency and haemoglobinopathy, the blood is tested for iron. A level below the bottom of reference range extends the diagnosis to iron-deficient microcytic anaemia. The reason for the vitamin B12 request is unclear, but as the result is within the reference range, then malnutrition as a cause seems unlikely.
- The diagnosis is not entirely unexpected given the history—Crohn’s disease being an inflammatory disorder of the intestines known to lead to malabsorption. Indeed, the inflammation may well contribute to the abnormal ESR. The referral to surgery may well have been to remove a section of diseased intestine.
- The next step is to initiate treatment. This is likely to be subcutaneous, intra-muscular or intravenous iron. Perhaps a month or six weeks later a follow-up FBC and ESR should show some response. However, Crohn’s is a chronic inflammatory disease, so that there may also be a suppression of erythropoiesis that may need immunosuppression to rectify.
5.2 Consequences of vitamin B12 deficiency
This case study describes a 75-year-old woman complaining of slowly developing fatigue causing her difficulty in getting out of her house. On examination, there is a swollen and painful tongue, and she complains of becoming forgetful, with occasional ‘tingling’ of her fingertips and numbness in her toes.
- Results outside the reference range are haemoglobin, MCV and ESR. This result, along with the history, is sufficient to confer the diagnosis of anaemia. With the MCV above the top of the reference range, we can extend the diagnosis to macrocytic anaemia. The abnormal ESR adds little to the diagnosis as it is the likely consequence of the anaemia.
- The key result is the low serum vitamin B12, which provides the most likely cause of the disease and symptoms. Indeed, the symptoms are typical. Normal iron levels seem likely to count against malnutrition. One could proceed to determine the precise cause of the deficiency, which, if found to be autoantibodies to gastric parietal cells or IF, will confer the diagnosis of pernicious anaemia. In most clear cases (such as this), examination of the bone marrow (to search for megaloblasts) seems unnecessary.
- The next step will be treatment with parenteral vitamin B12, with monitoring after several weeks to confirm its effect on the full blood count.
5.3 Anaemia after renal transplantation
- Azathioprine may be responsible for the anaemia as it suppresses the bone marrow
- With an MCV within the reference range, the anaemia is normocytic
- With an MCV below the reference range, the anaemia is microcytic
- The leading cause of microcytic anaemia is iron deficiency
- The patient probably had good iron stores in the liver and elsewhere that may have been slowly consumed by the disease process
- Yes. Azathioprine causes macrocytosis, so it is possible that it counteracted the effect of a lack of iron causing microcytosis. Once azathioprine was stopped, the red cells reverted to microcytes.
- As the patient is post-transplant, the practitioner will either be experienced with a case of this nature or will have sought expert opinion.
- Iron needs to be continued in order to build up the patient’s iron stores which were presumably depleted by the chemotherapy.
5.4 An anaemia of chronic disease
An 82-year-old man complains of being tired and lethargic. On examination, he is pale and there is a distended and painful abdomen. He also complains of periodic diarrhoea and constipation and recalls that he has lost perhaps a stone in the past year.
- The abnormalities are low haemoglobin and raised ESR. This, coupled with the history (being pale and complaining of tiredness and lethargy) is sufficient to give a diagnosis of anaemia. With an MCV within the normal range, we describe a normocytic anaemia.
- If the anaemia is normocytic then we are likely, at this stage, to eliminate failure to provide micronutrients to the bone marrow. It is also unlikely that there is a haemoproliferative disease within the bone marrow (such as leukaemia) as the white blood cell count and platelet count are both within the reference range. This, however, still leaves numerous possible reasons, such as haemolysis, and other tests could be used to exclude some diagnoses, such as a direct or indirect antiglobulin test for autoimmune or other anti-body-mediated haemolytic anaemia.
- In many cases, non-laboratory information can be useful, and the history can provide clues. There is loss of weight over a year, and gastrointestinal symptoms. This is indicative of several possible diagnoses, bowel malignancy among them. If this is the cause of the anaemia, one mechanism may be loss of blood into the faeces, which would normally be undetectable. This can be tested with the test ‘faecal occult blood’.