An atypical case of a 2-year-old boy with acute kidney injury: a race against time. Answers

The differential diagnoses considered were:

Additional tests included autoimmune antibody testing, the results of which were negative for antinuclear antibodies and anti-cytoplasmic neutrophilic antibody and an echocardiogram, which revealed a structurally normal heart with normal coronaries. No kidney biopsy was performed at this time.

In light of the clinical course and renal ultrasound image, KD was suspected, and intravenous immunoglobulin (IVIG; 2 g/kg body weight) was administered on the sixth day of illness. Since fever persisted, the treatment with IVIG was repeated 48 h later. The fever tapered, and the patient’s temperature normalized shortly thereafter while urinary output increased. The maximum levels of serum creatinine and blood urea nitrogen (BUN) were 2.12 and 103 mg/dl, respectively, but dialysis was not needed. Renal function improved gradually, with a lowering of the serum creatinine and BUN levels from the ninth day of illness, but the hematuria, proteinuria and leukocyturia persisted. The patient’s anemia worsened, and iron supplementation was started after an erythropoietin infusion. The patient developed thrombocytosis (maximum 1,000,000/μl), and the leukocyte count normalized. With this improved clinical status he was transferred to the general pediatric ward after 5 days on the pediatric intensive care unit. On the 13th day of illness he also developed peeling of the fingertips of both hands, which fulfilled the criteria for the complete form of KD. He was discharged soon afterwards in good clinical condition. Renal function completely recovered, and no coronary abnormalities were detected during follow-up.