A child with spider bite and glomerulonephritis: a diagnostic challenge.

A previously healthy 7-year-old white boy presented to St. Louis Children's Hospital with a 1-day history of headache, malaise, temperature of 38.7 degrees C, and a progressively erythematous, tender calf with central dusky purpura. On the morning of admission, his mother noticed a 2-mm crust on the patient's right calf with a 3-cm x 3-cm area of surrounding erythema. No history of recent trauma or bite was obtained. He had suffered two episodes of nonbloody, nonbilious emesis during the last day. In addition, over the previous 12 h, he presented brown urine without dysuria. His mother and brother had suffered from gastroenteritis over the previous week without bloody diarrhea. On initial physical examination, there was a 6-cm x 11-cm macular tender purpuric plaque with a central punctum on the right inner calf, which was warm and tender to the touch, with erythematous streaking towards the popliteal fossa (Fig. 1). The inguinal area was also erythematous with tender lymphadenopathy and induration, but without fluctuance. Laboratory studies included an elevated white blood cell count of 20, 800/microL with 6% bands, 86% segs, and 7% lymphocytes, hemoglobin of 12.5 g/dL, hematocrit of 35.1%, and platelets of 282,000/microL. The prothrombin time/activated partial tissue thromboplastin was 10. 4/28.0 s (normal PT, 9.3-12.3 s; normal PTT, 21.3-33.7 s) and fibrinogen was 558 mg/dL (normal, 192-379 mg/dL). Urinalysis showed 1+ protein, 8-10 white blood cells, too numerous to count red blood cells, and no hemoglobinuria. His electrolytes, blood urea nitrogen (BUN), and creatine were normal. The urine culture was negative. Blood culture after 24 h showed one out of two bottles of coagulase negative Staphylococcus epidermidis. The patient's physical examination was highly suggestive of a brown recluse spider bite with surrounding purpura. Over the next 2 days, the surrounding rim of erythema expanded. The skin within the plaque cleared and peeled at the periphery. The coagulase negative staphylococci in the blood culture were considered to be a contaminant. Cefotaxime and oxacillin were given intravenously. His leg was elevated and cooled with ice packs. The patient's fever resolved within 24 h. The lesion became less erythematous and nontender with decreased warmth and lymphadenopathy. The child was discharged on Duricef for 10 days. Because the patient experienced hematuria rather than hemoglobinuria, nephritis was suggested. In this case, poststreptococcal glomerulonephritis was the most likely cause. His anti-streptolysin-O titer was elevated at 400 U (normal, <200 U) and C3 was 21.4 mg/dL (normal, 83-177 mg/dL). His urine lightened to yellow-brown in color. His blood pressure was normal. Renal ultrasound showed severe left hydronephrosis with cortical atrophy, probably secondary to chronic/congenital ureteropelvic junction obstruction. His right kidney was normal.