A 5-year-old boy is brought to the pediatric clinic with concerns about progressive swelling in the face and legs over the past week. The caregiver first noticed puffiness around the eyes in the morning, which has since worsened. They also report that his urine appears frothy and that he has been more tired than usual. History of Present Illness Onset: Symptoms started one week ago Swelling pattern: Periorbital edema in the morning, worsening to leg and abdominal swelling throughout the day Urinary symptoms: Frothy urine No burning, urgency, or hematuria General symptoms: Increased fatigue No fever, rash, joint pain, or respiratory symptoms Medical History: No significant past medical history Family History: No known renal disease or autoimmune disorders Social History: Attends preschool, no recent infections or travel history Physical Examination General: Appears well but slightly fatigued Vital Signs: Blood Pressure: 98/62 mmHg (normal) Heart Rate: 88 bpm (normal) Respiratory Rate: 20 bpm (normal) Temperature: 98.6°F (37°C) HEENT: Periorbital edema, more pronounced in the morning Cardiovascular: Normal heart sounds, no murmurs Respiratory: No crackles or wheezing Abdomen: Mild ascites (fluid wave present) Extremities: Pitting edema in lower limbs Neurologic: Normal reflexes, alert and interactive Diagnostic Workup 1.Urinalysis 3+ proteinuria No RBCs or casts No leukocytes or nitrites 2.24-hour Urine Protein >3.5 g/day equivalent 3.Serum Studies Low albumin (2.1 g/dL) Hyperlipidemia (total cholesterol 280 mg/dL) Normal creatinine & BUN 4.Renal Ultrasound Normal kidney size and echotexture 5.Renal Biopsy Light Microscopy: Normal Electron Microscopy: Podocyte foot process effacement Which of the following is the most likely diagnosis in this case?
