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Difficulty: MediumMedical History Evaluation

An 81-year-old man is evaluated in the continuity clinic for a 4-month history of worsening fatigue, generalized weakness, and "pins and needles" sensations in both of his feet. He also reports recent episodes of unsteadiness while walking, leading to two minor falls. Past medical history includes type 2 diabetes mellitus, gastroesophageal reflux disease, primary hypertension, hyperlipidemia, and osteoarthritis of the knees. Past surgical history includes a laparoscopic cholecystectomy 10 years ago. Medications include metformin, omeprazole, lisinopril, atorvastatin, and acetaminophen as needed. He does not take any over-the-counter supplements. Laboratory studies reveal a hemoglobin of 9.4 g/dL and a mean corpuscular volume (MCV) of 115 fL. During the evaluation of this patient's medical history, which of the following documented elements represent independent risk factors for his current clinical and laboratory findings? (Select all that apply)

  1. A
    Routine administration of atorvastatin for hyperlipidemia
  2. Chronic daily therapy with omeprazole for gastroesophageal reflux diseaseAnswer
  3. C
    Prior laparoscopic cholecystectomy for symptomatic cholelithiasis
  4. Long-term use of metformin for glycemic controlAnswer
  5. E
    Routine administration of lisinopril for primary hypertension

Answer

The correct patient history elements are chronic daily therapy with omeprazole and long-term use of metformin, as both medications can independently cause Vitamin B12 deficiency.
The clinical picture of macrocytic anemia combined with peripheral neuropathy and ataxia is classic for Vitamin B12 (cobalamin) deficiency. When evaluating this patient's medical history, two independent pharmacological risk factors emerge. First, proton pump inhibitors like omeprazole significantly suppress gastric acid production. Gastric acid and pepsin are essential for cleaving dietary Vitamin B12 from carrier proteins, an early step required for its eventual absorption. Second, metformin is a well-established cause of Vitamin B12 malabsorption. It is believed to alter calcium-dependent membrane mobility in the terminal ileum, thereby impairing the absorption of the intrinsic factor-Vitamin B12 complex. Both of these daily medications independently increase his risk for this specific nutritional deficiency.

Step-by-Step Solution

1
Analyze the clinical presentation and laboratory results.
The patient has macrocytic anemia (MCV > 100 fL) and peripheral sensory neuropathy with ataxia.
Identifying the syndrome as Vitamin B12 deficiency is the critical first step in determining the underlying etiology.
2
Review the patient's medical and surgical history for causes of Vitamin B12 deficiency.
The patient's medication list includes omeprazole (a proton pump inhibitor) and metformin.
The medical history must be evaluated for established risk factors, including specific surgical procedures or medications that interfere with B12 absorption.
3
Correlate the identified risk factors with the pathophysiology of the disease.
Omeprazole reduces gastric acid required to cleave B12 from dietary proteins, and metformin impairs the calcium-dependent absorption of the B12-intrinsic factor complex in the terminal ileum.
Establishing a direct biological mechanism confirms these medications as the independent historical culprits.

Key Concept

Evaluating a patient's medication history to identify pharmacological causes of Vitamin B12 deficiency, specifically prolonged use of proton pump inhibitors and metformin.
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Topics

Medical History Evaluation

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