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55 CASE 55


A 65-year-old woman comes to the clinic complaining of weakness and lethargy.


The patient indicates that for the past 6 years she has had rheumatoid arthritis and has managed the pain by daily ingestion of a nonsteroidal anti-inflammatory drug (NSAID). During the past 6 months, she noted a decrease in stamina.



PHYSICAL EXAMINATION



VS: T 36°C, P 80/min, R 18/min, BP 90/70 mm Hg, BMI 22

PE: Patient is pale and thin. Physical examination is otherwise unremarkable.


LABORATORY STUDIES



Blood analysis: Hematocrit 25%

Blood smear: Megaloblastic cells (MCV 120 fL) and hypersegmented neutrophils

Serum vitamin B12: 90 pg/mL

Schilling test: Lack of absorption of vitamin B12.


DIAGNOSIS


Pernicious anemia



PATHOPHYSIOLOGY OF KEY SYMPTOMS


Red blood cell synthesis depends on adequate stores of iron, amino acids, and vitamins B6 and B12. Vitamin B12 is a water-soluble vitamin not produced by the body; consequently, it must be a component of the diet and absorbed through the gastrointestinal system. It is a common component of foods of animal origin.


Vitamin B12 absorption depends on gastric production of intrinsic factor. Intrinsic factor is secreted by gastric parietal cells, which bind to vitamin B12 in the stomach. The B12 intrinsic factor complex is absorbed by sodium-coupled transport in the terminal ileum and carried to the liver by the hepatic portal system. The liver can store up to 3 years worth of vitamin B12. Therefore, dietary deficiency is rare except in vegans who avoid all animal products.


Pernicious anemia results from a defect in the production of intrinsic factor. This defect can be due to an autoimmune disease or from chronic gastritis. Vitamin B12 is also necessary for normal nerve function, and chronic B12 deficiency can include neurologic symptoms such as tingling or numbness of the hands and feet and loss of balance.


The absence of vitamin B12 leads to the synthesis of a decreased number of red blood cells, but the individual red blood cells are larger than normal. This leads to the characterization of the disorder, which is macrocytic megaloblastic anemia.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 55

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