Thrombotic Microangiopathy and Glomerulonephritis Complicating Staphylococcus aureus-Induced Impetigo in a Girl

To the Editors: An 8-year-old girl with atrophic thyroiditis treated with levothyroxine developed painful facial impetigo refractory to approximately 1 month of oral antibiotics and was referred to our hospital. Multiple erythematous lesions with crusts were observed on the face and auricles, some erosive, with bilateral lower-leg pitting edema. Laboratory tests showed Table 1. Based on the cutaneous findings, a diagnosis of impetigo was made. The combination of hemolytic anemia with schistocytes, thrombocytopenia and renal dysfunction led to a diagnosis of thrombotic microangiopathy (TMA). Marked proteinuria and hematuria suggested concomitant acute glomerulonephritis. Cefazolin and fluid restriction were initiated. On hospital day 4, the serum albumin level fulfilled the criteria for nephrotic syndrome. By day 8, the impetigo had resolved, and cefazolin was discontinued. On hospital day 13, hemolytic anemia, hypoalbuminemia, hematuria and proteinuria improved (Table 1), and she was discharged. Culture of the impetigo lesions yielded methicillin-sensitive Staphylococcus aureus (MSSA). Genetic analysis of this strain detected the exfoliative toxins B (etb) and the α-hemolysin gene (hla), whereas genes for enterotoxin-related toxins such as sea and for tsst were not detected. Other evaluations, including stool culture, ADAMTS13 activity, antistreptolysin O titer, hemolysis testing, and anti-complement factor H antibodies, showed no abnormalities. Day 84, laboratory data showed full recovery without relapse of TMA or acute glomerulonephritis (Table 1). TABLE 1. - Laboratory Data During the Disease Day 1 Day 4 Day 5 Day 6 Day 13 Day 84 WBC (/μL) 5300 6200 6400 7700 5300 5500 Hb (g/dL) 10.8 8.5 8.1 7.8 8.6 11.5 PLT (×104/μL) 10.2 3.6 5.8 9.0 54.1 35.6 T-bil (mg/dL) 1 0.8 0.3 0.2 LD (U/L) 557 874 781 644 397 237 Alb (g/dL) 2.8 2.1 1.8 2.6 3.4 3.8 BUN (mg/dL) 21.8 18.5 21.0 22.8 12.9 8.5 Cr (mg/dL) 0.65 0.70 0.68 0.66 0.53 0.30 IgG (mg/dL) 1256 IgA (mg/dL) 155 IgM (mg/dL) 156 C3 (mg/dL) 115 C4 (mg/dL) 34 Haptoglobin (mg/dL)