Pica

Pica is an eating disorder of persistent consumption of non-nutritive, non-food substances over a period of at least one month. Examples include ice, chalk, soil, paper, hair and paint, and in specific circumstances other inedible material.

The behaviour is developmentally inappropriate and is not part of a culturally supported or socially normative practice.

It occurs in intellectual disability, autism spectrum disorder, pregnancy and iron deficiency. In iron deficiency, the term pagophagia describes the well recognised pattern of compulsive ice consumption.

The underlying cause and risk profile vary substantially with clinical context, so assessment and management are individualised.

Pathophysiology

• The mechanism linking pica to iron deficiency, and less consistently to other micronutrient deficiencies including zinc deficiency, is incompletely understood.
• The association is well established, and the behaviour resolves with correction of the deficiency in many affected individuals. This supports a genuine, mechanistically unclear physiological relationship rather than a coincidental one.
• In intellectual disability or autism spectrum disorder, pica is believed to reflect sensory seeking behaviour and reduced awareness of the inappropriate or harmful nature of the ingested material. In some cases it serves a self soothing or repetitive function. This differs from the deficiency driven mechanism proposed in iron deficiency.
• Pregnancy related pica is not fully understood. It is proposed to relate to the physiological iron demands of pregnancy and the frequently coexisting iron deficiency.
• In some cultures, traditional beliefs about ingesting particular substances in pregnancy also contribute, most classically clay or soil, termed geophagia.

• The substance consumed varies with context and individual pattern. Ice (pagophagia) is particularly characteristic of iron deficiency, while a broader range of substances may be consumed in intellectual disability or autism spectrum disorder.
• Medical complications reflect the substance ingested: dental damage with ice, gastrointestinal obstruction or perforation with larger or sharp non-food items, lead poisoning with lead containing paint or contaminated soil, and intestinal parasitic infection with geophagia in endemic regions.
• The pattern of substance consumed therefore directly informs the targeted medical risk assessment.
• Features of the underlying associated condition frequently accompany pica. These are symptoms of iron deficiency anaemia, or the broader clinical features of intellectual disability or autism spectrum disorder. Assessment for them is an essential part of evaluation.
• In children, mild, transient mouthing or occasional ingestion of non-food items is normal developmental exploration at certain ages. Diagnosing pica requires behaviour that is persistent, developmentally inappropriate for the child's age, and clinically significant.

• Diagnosis is established through a detailed clinical history exploring the specific substance or substances consumed, the frequency and duration of the behaviour, and the broader clinical context (including any known intellectual disability, autism spectrum disorder, pregnancy status, or symptoms suggestive of iron deficiency).
• Full blood count and iron studies are essential in every case given the strong, well recognised association with iron deficiency, and this assessment may reveal the underlying, previously unrecognised iron deficiency that is directly amenable to treatment.
• Blood lead level assessment is appropriate where there is a relevant history of ingesting lead containing material (paint, contaminated soil, certain traditional remedies or cosmetics in specific cultural contexts) given the risk of significant lead toxicity with this specific exposure.
• Abdominal imaging (plain radiography, or, where clinically indicated by symptoms suggesting obstruction or perforation, further cross-sectional imaging) is warranted where there is concern regarding ingestion of a potentially obstructing or otherwise harmful foreign material, or where relevant abdominal symptoms are present.
• Stool examination for ova and parasites is appropriate where geophagia has occurred, particularly in or following travel to an endemic region, given the associated risk of soil transmitted parasitic infection.

• Correct any identified iron deficiency, following standard iron replacement principles (see iron deficiency anaemia). This frequently resolves the pica. It is both a therapeutic intervention and, in a sense, a confirmatory response supporting the causal association.
• Pica in intellectual disability or autism spectrum disorder needs a structured behavioural approach, generally with specialist input from psychology or behavioural therapy services.
• Modify the environment to reduce access to potentially harmful substances. Where relevant, address any sensory or self soothing function of the behaviour through appropriate alternative strategies.
• Treat any medical complication of the ingested substance according to the principles for that complication. Examples are lead poisoning, surgical or endoscopic intervention for gastrointestinal obstruction or a retained harmful foreign body, and antiparasitic treatment for confirmed soil transmitted helminth infection following geophagia.
• Provide nutritional counselling and support. In pregnancy, discuss culturally sensitive practices and beliefs relevant to the individual patient.
• Certain pica behaviours, particularly geophagia, have a recognised cultural and traditional context in some populations. Use a sensitive, non-judgmental approach that does not dismiss culturally embedded practices, while still addressing any genuine medical risk.
• Follow up regularly. Reassess iron status where iron deficiency was the underlying cause, and monitor for medical complications given the substance history.