The 12-Month Visit With a Bottle of Milk and a Low Ferritin
At a WIC-affiliated clinic, you see M.G., a 12-month-old girl, for her well-child visit. She was exclusively breastfed for 6 months, then continued breastfeeding alongside table foods her mother describes as "mostly rice, beans, and tortillas." For 4 months she has drunk about 32 oz of whole cow's milk daily from a bottle and takes little meat or fortified cereal; she goes to sleep with a bottle. Weight 9.8 kg (50th percentile), length 25th percentile. Hemoglobin 10.2 g/dL, MCV 72 fL, RDW elevated, ferritin 8 ng/mL, RBC 5.6 million/µL. The family receives WIC, shares a car with two other households, and the father recently lost his job. The mother speaks Spanish and declines an interpreter, saying her 10-year-old can translate instead.
1. Interpret the CBC and ferritin. Is this iron deficiency anemia, thalassemia trait, or anemia of inflammation, and what would you do to be sure?
Read the worked answer
Pattern: microcytic anemia (Hb 10.2, MCV 72 fL) with a high RDW and a low ferritin. A ferritin of 8 ng/mL is below the 12 ng/mL threshold for iron deficiency even without inflammation; if CRP were elevated you would use <30 ng/mL, because ferritin is an acute-phase reactant.
Why not thalassemia trait: the high-normal RBC count and borderline Mentzer index (72 ÷ 5.6 ≈ 12.9) can tempt that label, but trait usually shows a normal RDW, normal or high ferritin, target cells, and microcytosis out of proportion to the anemia. A ferritin of 8 with a high RDW is not explained by trait alone.
Why not anemia of inflammation: ferritin would be normal-to-high with a low TIBC. That is not this picture.
So: iron deficiency anemia, mechanistically driven by 32 oz/day of cow's milk (displaces iron-rich food and can cause occult GI blood loss) plus prolonged bottle use.
Confirm the mechanism, not the diagnosis:
- Check CRP if there is any concern for inflammation.
- Check a lead level - iron deficiency increases lead absorption, and 12 months is a screening point.
- If microcytosis persists after iron repletion, order hemoglobin electrophoresis with HbA2 to exclude coexisting trait.
2. Write the treatment and monitoring plan, including the iron dose and the timing of follow-up labs.
Read the worked answer
Dose: elemental iron 3 mg/kg/day once daily = about 30 mg/day for 9.8 kg (range 3-6 mg/kg/day). Once-daily dosing is as effective as divided dosing and improves adherence. Give ferrous sulfate drops between meals with a vitamin C source, never with milk; expect dark stools; brush teeth or use a straw to limit staining; counsel on overdose risk and safe storage.
Diet:
- Cap cow's milk at 16-24 oz/day from an open cup; stop the bedtime and nap bottles (caries risk too).
- Pair iron-rich foods (pureed meat, beans, lentils, eggs, fortified infant cereal) with vitamin C.
- Avoid tea, which chelates iron.
Monitoring:
- Reticulocyte count at 1-2 weeks if you want early confirmation.
- Repeat CBC at 4 weeks - expect an Hb rise of at least 1 g/dL.
- Continue iron for 3 months after the Hb normalizes to refill stores, then recheck ferritin.
If the 4-week Hb has not risen: check adherence and administration technique first, then consider ongoing blood loss, malabsorption/celiac disease, acid suppression, lead, or a hemoglobinopathy. Repeat ferritin with CRP and order hemoglobin electrophoresis.
3. The mother has declined an interpreter. Which anticipatory guidance matters most at this visit, and how do you handle the interpreter refusal and the family's social situation?
Read the worked answer
Do not use the 10-year-old. A child interpreter produces errors, role reversal, and lost nuance; it also fails the clinic's obligation to provide meaningful access. Frame it as clinic policy rather than a judgment of her: "We always use our own interpreter so you get the same information as everyone else." Use phone/video interpretation, document the offer and the use, and flag her chart for a Spanish-speaking clinician at the next visit.
Anticipatory guidance for 12 months:
- Vaccines: MMR, varicella, hepatitis A, PCV, Hib; influenza annually.
- Lead screening and the 4-week anemia recheck.
- Dental home and fluoride varnish; wean the bottle; no juice.
- Screen time: none under 18 months; car seat kept rear-facing as long as the seat allows; water safety; sleep.
- Iron-specific teaching: why the milk limit, how much, which foods, how to give the iron.
Social situation:
- Screen for food insecurity (Hunger Vital Sign), recertify WIC, connect to SNAP, food pantry, 211, and social work.
- The shared car and job loss affect her ability to return - build follow-up around it (4-week visit, phone reminder, same-day-as-WIC if possible).
- Close the loop with teach-back and a Spanish-language handout.