A 3-year-old boy from rural Maharashtra is brought to the primary health centre by his mother with a 6-month history of poor weight gain and recurrent infections. On examination, he weighs 10 kg (expected weight for age: 15 kg), height 85 cm, with visible wasting of muscles and subcutaneous fat. His hair is sparse, thin, and depigmented. Serum albumin is 2.2 g/dL (normal: 3.5–5.0 g/dL), and total serum protein is 5.1 g/dL. The child is alert and playful. Which form of protein-energy malnutrition (PEM) is this child most likely suffering from?