Does WHO Recognize Acute-on-Chronic Malnutrition in Pediatrics?
No, the WHO does not recognize "acute-on-chronic malnutrition" as a formal diagnostic category in children. 1
Current International Classification Framework
The WHO and ESPEN (European Society for Clinical Nutrition and Metabolism) classify pediatric malnutrition by etiology and inflammatory status, not by temporal patterns such as "acute-on-chronic." 1 The recognized categories are:
- Disease-related malnutrition (DRM) with inflammation – includes both acute (e.g., sepsis, severe infection) and chronic inflammatory conditions (e.g., cancer, chronic organ failure) 2, 1
- Disease-related malnutrition without inflammation – caused by impaired intake or absorption without measurable inflammation 2, 1
- Malnutrition without disease – hunger-related or socioeconomic malnutrition 2, 1
WHO Monitoring Indicators for Pediatric Malnutrition
The WHO tracks two distinct forms of malnutrition in children under 5 years, measured independently: 2
- Stunting (height-for-age >2 SD below median) – reflects chronic or recurrent undernutrition 2
- Wasting (weight-for-height >2 SD below median) – reflects acute malnutrition from poor nutrient intake or disease 2
These are separate diagnostic entities, not combined into an "acute-on-chronic" classification. 2
Clinical Scenarios That May Appear "Acute-on-Chronic"
When a child with pre-existing chronic malnutrition (e.g., stunting, cancer-related cachexia) develops an acute illness (e.g., pneumonia, sepsis), the classification should be based on the dominant current pathophysiology—in this case, acute disease-related malnutrition with inflammation—while acknowledging the baseline nutritional compromise. 1 However, this does not constitute a separate diagnostic category. 1
Example: Food Protein-Induced Enterocolitis Syndrome (FPIES)
One pediatric condition that uses similar terminology is FPIES, where an "acute-on-chronic phenotype" describes neonates who initially present with chronic symptoms but develop acute reactions upon re-exposure. 2 This is a disease-specific descriptor, not a WHO-recognized malnutrition classification. 2
Why This Distinction Matters for Clinical Practice
The term "acute-on-chronic malnutrition" should not be used in formal documentation or treatment algorithms because it lacks standardized diagnostic criteria and is not recognized in WHO or ESPEN guidelines. 1 Instead:
- Nutritional intervention strategies must be guided by the specific etiological category (DRM with/without inflammation) and the inflammatory status of the patient 1
- Diagnostic thresholds (BMI cut-offs, percentage weight loss, reduced muscle mass) apply uniformly regardless of whether malnutrition is acute, chronic, or both 1
- Treatment planning requires identifying the dominant pathophysiology driving current nutritional compromise 1
Practical Implications for Risk Stratification
In settings where children may have both chronic undernutrition and acute illness, WHO guidelines recommend identifying specific risk factors that warrant referral or closer monitoring: 2
- Moderate malnutrition (mid-upper arm circumference 115-135 mm or weight-for-age Z-score -2 to -3) increases mortality risk in children with acute illness (OR 1.73-2.46) 2
- Children with unknown nutritional status in resource-limited settings should be assessed for malnutrition when presenting with acute illness 2
- Severe wasting and kwashiorkor are classified as severe acute malnutrition (SAM), not "acute-on-chronic," even when occurring in chronically undernourished populations 3
Common Pitfall to Avoid
Do not conflate the coexistence of stunting (chronic) and wasting (acute) in the same child with a distinct diagnostic entity called "acute-on-chronic malnutrition." 2, 1 These remain independent indicators that identify different patient groups and require separate documentation. 2, 4 MUAC and weight-for-height Z-score identify different subgroups of malnourished children and should be used independently, not combined into a single temporal classification. 4, 5