The patient was a 10-year-old boy who presented with eyelid edema on awaking the day before admission. He attended a local hospital, which confirmed proteinuria 3+, and he was referred to our hospital for admission. Based on the patient's weight gain of approximately 3 kg, mild anorexia, and clinical examination, he was diagnosed with primary nephrotic syndrome and was admitted to the hospital. He had no medical history and was on no medication. Before admission, he lived with his mother and sister, and his father worked away. He played basketball three times a week as a club activity. Written consent was obtained from the patient and his parents for publication of this case report.
Physical examination revealed the following: height 134.6 cm, weight 27.2. kg; blood pressure (BP) 122/66 mmHg; heart rate (HR) 93/min, and oxygen saturation 99%. Blood chemistry showed total protein 4.0 g/dl, serum albumin (Alb) 1.2 g/dl, blood urea nitrogen (BUN) 16 mg/dl, creatinine (Cr) 0.46 mg/dl, Na 139 mEq/l, white blood cell count 4460/mul, C-reactive protein 0.1 mg/dL, and hematocrit 38.7%. Urine testing showed a urine protein level of 1189 mg/dL and a urine creatinine level of 185.8 mg/dL, resulting in a urine protein/creatinine ratio (UP/Cr) of 6.4. A cardiothoracic ratio of 48.7 was assessed on chest radiography, with no iliopsoas image. Abdominal ultrasonography showed slight renal hyperintensity and ascites.
Prednisolone (PSL) was started at 50 mg (2 mg/kg/day) on the 3rd day. After admission, weight and edema decreased, whereas systolic BP remained in the 120-130 mmHg range, and 2 mg enalapril maleate was started on the 5th day. UP/Cr was below 2.0,) the definition of nephrotic syndrome in pediatric patients, after the 12th day. Therefore, the effects of PSL treatment were evident, and renal function was expected to improve, so rehabilitation was started on the 15th day. The patient was independent in all activities of daily living at the start of rehabilitation.
Physical function was evaluated on days 15, 29, and 51 of hospitalization. Measurements included grip strength, knee extension strength, the sit-up test, side-step test, sit-and-reach test, and 6-min walk test (6 MWT).
Grip strength was measured using a Smedley digital hand dynamometer with the patient in a standing posture. Measurements were made twice, alternately on the right and left sides, and the average of the highest value on each side was used. Knee extension strength was measured using a hand-held dynamometer (mu-tas F1, ANIMA, Tokyo, Japan) in a sitting square, with the hip and knee at 90  flexion.) The sit-up, side-step, and sit-and-reach tests were performed according to the method described in the new fitness test recommended by the Ministry of Education of Japan.) In the sit-up test, a test of trunk muscle strength, the number of times both elbows touched both thighs in 30 s was counted with the patient starting from a supine position with both arms folded in front of the chest and both knees held at 90 . The side-step test, an agility test, was measured using three lines drawn at intervals of 100 cm as the measurement area; the patient stands straddling the center line and, at the "start" signal, side-steps until crossing or touching one sideline, then returns to the center line and side-steps again until crossing or touching the opposite line. The measurement time was 20 s, and the number of times the center line was crossed was recorded. The sit-and-reach test, as a flexibility test, was measured by placing both legs in the flexibility box, and with both arms stretched out at shoulder width, the box was pulled forward with both hands to assume a long-sitting posture. The patient slowly bends forward and moves the slider on the box straight ahead as far as possible, taking care to keep the hands one above the other and not to bend the knees. The distance the slider was moved by the outstretched clasped hands when bending forward was measured. The 6 MWT was measured by walking as fast as possible along a marked indoor corridor and recording the total distance traveled after 6 min according to the methodology of the American Thoracic Society.)
Alb, BUN, eGFR, and UP/Cr were obtained from medical records. UP/Cr was examined to evaluate the safety of rehabilitation. The measurement period was from the 19th day, just after the start of weekly rehabilitation, to the 54th day, the day of discharge.
Resistance training, balance exercise, and aerobic exercise therapy were administered for 40 min, five times a week. For resistance exercise, calf raises and squats were performed as 2-3 sets of 20 repetitions, and for balance exercise, 2-3 sets of standing on one leg for 1 min on each side were performed. Aerobic exercise was performed on a bicycle ergometer for 20 min at an intensity of 60% of the peak work rate (peak WR) calculated in the exercise tolerance test, and the Borg scale and heart rate were monitored and adjusted accordingly. Systolic BP, diastolic BP, and HR before and after rehabilitation during hospitalization were measured, and the average values were calculated. Karvonen's formula determined the percentage of the HR during aerobic exercise to the maximum HR measured in the exercise tolerance test. The exercise tolerance test was performed only once as an initial evaluation using a bicycle ergometer to measure peak WR. The protocol of the exercise load test was a 3-min warm up followed by a multistep incremental load of 10 W/min at 50 rpm. Improving balance, muscle strength, and exercise tolerance are important for maintaining athletic performance in basketball, the patient's preferred sport. Therefore, balance training was included in the exercise program for this patient.
After the start of exercise therapy, the patient was steroid resistant. A renal biopsy was performed on the 34th day, and the patient was diagnosed with minimal change nephrotic syndrome. Subsequently, steroid pulse therapy was administered twice for three days, from 41st to 43rd and 48th to 50th day. No adverse events were observed before or after renal biopsy or steroid pulse therapy. The PSL dose was reduced to 25 mg on the 43rd day. The blood glucose level before breakfast was 142 mg/dl on day 49, indicating steroidal hyperglycemia, but this had decreased to normal levels on day 54. The patient was discharged home on the 54th day, and PSL 25 mg and an angiotensin-converting enzyme inhibitor 2 mg were administered. After discharge from the hospital, the patient was treated with pulse steroid therapy once a month, and cyclosporine A was considered after 4-6 months, depending on the response to pulse steroid therapy. The amount of energy provided by the patient's diet was increased from 2000 to 2300 kcal from the 25th day.
From the 15th to the 33rd day, resistance exercise, balance exercise, and aerobic exercise were performed on the lower limbs. Bed rest was ordered until a renal biopsy was performed on the 34th; on the 35th day, based on the biopsy findings, the patient was released from bed rest. From the 36th day onward, bedside exercises for the lower limbs and gait training in the ward were performed. The amount of exercise was gradually increased. During steroid pulse therapy, exercise therapy was administered in the afternoon after the steroid pulse. During the 43rd-53rd day, lower limb resistance exercise, balance exercise, and aerobic exercise were resumed.