
CDC Home

Case Studies

The following case studies are not actual patients. They combine elements from different cases to emphasize important aspects of vitamin B12 deficiency.

Case Study 1


During a checkup for hypertension, a 65-year-old female reports about 2 months of tiredness, feeling faint from “getting up too fast”, and “memory problems”.

Case Study Question 1

Do any of the presenting complaints raise your index of suspicion about a possible B12 deficiency? If so, why? Check your answer to question 1.


On review of symptoms, she reports difficulty concentrating, fatigue, feeling faint when she stands quickly, and vague gastrointestinal discomfort with some decrease in appetite.

She denies any history of previous trauma, diplopia, dysphagia, vertigo, vision loss, loss of consciousness, back pain, or symptoms of bowel or bladder dysfunction.

Her family history is negative for neurologic, psychiatric, and autoimmune diseases. Her medications include an antihypertensive as well as an occasional anti-inflammatory drug for episodic headache. Social history reveals a single woman who smokes about one-half pack of cigarettes per day, drinks alcohol only socially, and denies illicit drug use. She has a high school education and, until recently, has worked in the office of a trucking company.

Case Study Question 2

What risk factors does this woman appear to have for a vitamin B12 deficiency? Check your answer to question 2.

Physical Examination

Pale 65 y.o. WF who appears well-nourished, alert, and oriented.

Summary of Physical Examination
Vital SignsT-98.6, HR-76, R-18, B/P-130/80 supine and 95/52 upon standing
Height/Weight5'4"/120 lbs.
HeadNormocephalic; oropharynx clear but pale; palpebral conjunctivae pale
NeckSupple, full active and passive ROM without pain, without audible bruits; no lymphadenopathy; no thyromegaly
BackNo spine tenderness
LungsClear to auscultation
HeartRegular rate and rhythm; no murmurs
AbdomenSoft, nontender; no organomegaly
RectalNormal rectal tone; no fissures
ExtremitiesNo clubbing, cyanosis, or edema; FROM
SkinPale; no rash

The general physical exam is unremarkable except for orthostatic hypotension and weight loss of 3 pounds since her last visit 6 months ago. She is alert and oriented times three. Her Mini-Mental Status Exam score is 26 out of 30. She misses one point on serial 7s and is able to recall three of three items. There is evidence of bilateral mildly diminished vibration and proprioception. Her reflexes are 3+/4+ throughout with negative Babinski reflex.

Summary of Neurological Examination
Cranial NervesII—Visual acuity 20/25 in both eyes (corrected); normal fundoscopic exam; visual fields intact with no central scotoma
III, IV, VI—Extraocular movements intact; pupils equal, round, and reactive to light with no afferent pupillary defect
V, VII, XII—Intact facial sensation; intact masseter motor strength, without dysarthria; tongue protruded in midline
VIII—Hearing grossly normal
XI, X—Swallowing intact
XI—Muscle strength equal bilaterally
MotorNormal muscle bulk; muscle strength 5/5 in all muscle groups
CerebellarNormal finger-to-nose, heel-to-shin, and rapid alternating movements

Case Study Questions

3. Does the fact that she appears to be "well-nourished" indicate she is unlikely to have a vitamin deficiency? Why or why not? Check your answer to question 3.

4. Are there any aspects of her physical examination that suggest a vitamin B12 deficiency? Check your answer to question 4.

5. Given her history and physical examination findings, what laboratory test(s) would you order? Check your answer to question 5.

Laboratory Studies

You order routine laboratory studies, which include complete blood count (CBC) with smear and chemistry screen. In addition, you order a serum vitamin B12 level to investigate further the etiology of her fatigue and pale mucosa. Results from the CBC and smear reveal a borderline macrocytic anemia. The chemistry panel is within normal limits. The serum vitamin B12 level you requested is 215 picograms per milliliter (pg/mL). This level is considered within a “normal range” by some laboratories, but you take into account her other signs and symptoms and request confirmatory testing with methylmalonic acid (MMA) and homocysteine (Hcy) levels.

Results of Confirmatory Testing

Both MMA and Hcy levels are elevated. Her MMA is greater than 0.5 micromoles per liter (μmol/L), and her Hcy is greater than 17 μmol/L, confirming your suspicion that this patient has a vitamin B12 deficiency.

You decide to investigate the cause of her vitamin B12 deficiency. Although she denies a history of pernicious anemia in her family and she has had no previous indication of autoimmune diseases, you order an anti-intrinsic factor (IF) antibody test that confirms the presence of pernicious anemia.


You explain that with the diagnosis of pernicious anemia she will have to continue vitamin B12 therapy for the remainder of her life, and you make a note on her chart to assess her compliance at each visit. You also advise her to inform her family of the diagnosis since there is possibly a genetic component.

You start the patient on vitamin B12 intramuscular (IM) injections. She gets IM cyanocobalamin 1,000 micrograms (mcg) two times per week for 2 weeks and then switches to oral vitamin B12 1,000 mcg daily thereafter. Almost immediately after the initiation of injections, she reports improved concentration. Within 2 weeks, she notes less fatigue and normal appetite.


Learn More about Health Insurance Market Place

Flu and disabilities button

Contact Us:
  • Centers for Disease Control and Prevention

    National Center on Birth Defects and Developmental Disabilities

    Division of Birth Defects and Developmental Disabilities

    1600 Clifton Road
    MS E-87
    Atlanta, GA 30333
  • 800-CDC-INFO
    TTY: (888) 232-6348