A 3-year-old child from rural Maharashtra presents with severe wasting, loss of muscle mass, and preserved subcutaneous fat. On examination, the child is alert and has normal serum albumin. Which investigation is most appropriate to confirm the diagnosis and assess severity?

Explanation

## Diagnosis of Marasmus vs Kwashiorkor **Key Point:** The clinical presentation—severe wasting with preserved subcutaneous fat and normal serum albumin—is pathognomonic for **marasmus**. MUAC is the gold-standard field investigation for assessing protein-energy malnutrition severity. ### Why MUAC is the Investigation of Choice **High-Yield:** MUAC <11.5 cm in children 6–59 months indicates severe acute malnutrition (SAM) and correlates directly with muscle mass depletion. It is: - Non-invasive, field-applicable - Highly sensitive for detecting wasting - Independent of age (unlike weight-for-height) - Predictive of mortality risk in PEM ### Differential Features: Marasmus vs Kwashiorkor | Feature | Marasmus | Kwashiorkor | | --- | --- | --- | | **Muscle mass** | Severely wasted | Relatively preserved | | **Subcutaneous fat** | Depleted | Preserved | | **Serum albumin** | Normal or low | **Low (<2.8 g/dL)** | | **Edema** | Absent | Present (pitting) | | **Hair changes** | Sparse, thin | Flag sign, easy pluckability | | **Skin lesions** | Minimal | Dermatitis, hyperpigmentation | | **Investigation of choice** | **MUAC** | Serum albumin, prealbumin | **Clinical Pearl:** In this case, normal serum albumin rules out kwashiorkor; the clinical picture (wasting + preserved fat) confirms marasmus. MUAC quantifies severity and guides nutritional rehabilitation. ### Role of Other Investigations - **Serum prealbumin:** Sensitive for protein status but reflects recent intake (half-life 2–3 days); not diagnostic of marasmus specifically. - **Total lymphocyte count:** Reflects immune status and protein depletion but is non-specific and influenced by infection. - **24-hour urinary creatinine:** Reflects muscle mass indirectly but is cumbersome in field settings and not a first-line diagnostic tool.