Thread by @acweyand

An 18 month old boy presents to your office for a well child visit.

Parents have no concerns but do mention that he eats a lot of paper.

You astutely decide to check a CBC and iron studies but wonder why iron deficiency causes this strange symptom?

#hemetweetorial 🧵
1/

Pica in medicine refers to the compulsive eating of non edible substances.

It is classified as an eating disorder.

The word pica originates from Latin referring to the magpie which eats indiscriminately.

Pica was described by Hippocrates as “corruption of the blood”

2/

In 40 AD Cornelius Celsus noted that those with bad color suffer from a malacia (craving for non food)

The Swahili term for anemia was mistranslated as “disease of earth eating”

3/

More specific terms exist for certain substances.

Geophagy:earth
Pagophagy:ice
Rhizophagy: uncooked rice
Amylophagy: starch
Cautopyreiophagia: burnt matches
Lithophagy: stones
Xlophagy: wood
Tricophagy: wool, hair
Acuphagy: sharp objects
Plumbophagy: lead

4/

Not all pica is pathologic as in some cultures it can be culturally acceptable.

In the US, pagophagy (ice) is most commonly seen.

It has been suggested that chewing ice elicits vasoconstriction, increasing brain perfusion in fatigued iron deficient patients.

5/

This theory is supported by a study that found iron deficient pts performed better on neuropsychological testing when allowed to chew ice.

The theory that ice relieves the pain of glossitis & stomatitis is less accepted given very quick resolution of pica w/repletion.

6/

A meta analysis found pica in 28% of pregnant pts and in many cultures it is considered pathognomonic of early pregnancy.

There is a strong association w/ iron deficiency (ID) w/1 study finding pica in 55% of ID pts.

The direction of this relationship is up for debate.

6/

One adaptive theory is that pica is an attempt to compensate for deficiency.

Iron, zinc & calcium deficiency may alter appetite regulating brain enzymes, stimulating unusual cravings.

One child chewing bricks was picked up by her dentist due to severe dental attrition.
7/

In geophagy, soil & clay ingested inhibit iron absorption perpetuating a vicious cycle.

In plumbophagy (lead) iron deficiency increases lead absorption exacerbating lead toxicity.

Burton’s line (lead sulfide deposition between teeth & gums) may be seen.

8/

Studies show resolution of pagophagy (ice) w/iron repletion but this finding is less consistent w/other substances.

The substances ingested often don’t contain iron, arguing against this adaptive theory.

Geophagy is more common w/white clay than iron rich red clay.

9/

Pica is less common in the 3rd trimester when iron needs are highest.

A strong association is seen w/celiac disease suggesting a possible role for iron malabsorption.

A gluten free diet is often sufficient for symptom resolution.

10/

A second adaptive theory is that geophagy provides protection from enterotoxins or parasites either by direct binding or decreased permeability of the gut wall.

A large review of geophagy in humans & animals came to the conclusion that human geophagy is protective.

11/

Support for this includes
✨accompanied gastrointestinal distress & ingestion of toxic chemicals
✨clay adsorption
✨high prevalence in tropics
✨high prevalence when protection needed (ie pregnancy)

In contrast, animals derive protection AND micronutrients from geophagy

12/

Non adaptive theory is that pica is due to ⬇️ iron in tongue, olfactory apparatus, or brain.

Data in rats suggests DMT1, an iron transporter, is involved in olfactory & gustatory function.

A study in women found iron deficiency to be associated w/hypogeusia (⬇️ taste)

13/

It has also been suggested that iron scarcity in the hippocampus may contribute.

Pica can also be associated with a number of psychiatric diagnoses.

Pica is underreported as clinicians don’t ask & patients may lack understanding of its relevance or feel ashamed.

14/

Complications can include tooth damage, gastrointestinal discomfort, intestinal obstruction, electrolyte disturbances, and poisoning.

Image: Intestinal obstruction 2/2 lithobezoar

15/

Recognition is important to identify nutrient deficiencies & educate patients on the risk of significant complications.

Treatment for pica is directed at the underlying disorder.

Image: CNS changes 2/2 paradichlorobenzene toxicity from mothball ingestion.

16/

So why does iron deficiency cause pica?

⚠️Multiple theories (both adaptive and non adaptive) exist
⚠️each theory is supported and refuted by some of the evidence
⚠️no theory can explain all cases

17/fin