Proximal muscle weakness atrophy in a child with PEM due to which electrolyte disturbance:

C i.e. HypophosphatemiaRef: Nelson, Textbook of Pediatrics, 20th edition, page 833Explanation:Hypokalemia:* Heart and skeletal muscle (muscle weakness and cramps) are especially vulnerable to hypokalemia* Paralysis is a possible complication, generally only at levels <2.5 mEq/L (starts with the legs, followed by the arms)* Slows gastrointestinal motility (constipation levels <2.5 mEq/L)* Impairs bladder function, potentially leading to urinary retention* Causes polyuria and polydipsiaHypocalcemia:* Muscular pain and cramps are early manifestations; they progress to numbness, stiffness, and tingling of the hands and feet positive Chvostek or Trousseau sign or laryngeal and carpopedal spasms.* Convulsions with or without loss of consciousness teeth erupt late and irregularly. Enamel formation is irregular, and the teeth may be unusually soft.Hypophosphatemia:* Hypophosphatemia is a serum phosphate concentration < 2.5 mg/dL (0.81 mmol/L)* Hemolysis and dysfunction of white blood cells.* Proximal muscle weakness and atrophy* Rhabdomyolysis* Cardiac dysfunction* Neurologic symptoms, such as tremor, paresthesia, ataxia, seizures, delirium and comaHypomagnesaemia:* Magnesium levels <0.7 mg/dL* Causes secondary hypocalcemia by impairing the release of PTH by the parathyroid gland and through blunting the tissue response to PTH* Dominant manifestations of Hypomagnesaemia are due to hypocalcemia: tetany, positive Chvostek and Trousseau signs and seizures