Case 2: Where have all the white cells gone?

Abstract

A 23-month-old girl with a significant history for preseptal cellulitis at three months of age and pneumonia at 14 months of age presented to the emergency department (ED) with chief complaints of fever, tachypnea and cough. She was initially seen in the ED five days before admission with a five-day history of persistent fever, despite recent use of antibiotics (cephalexin, then azithromycin) for acute otitis media and pharyngitis, which were diagnosed by her family physician. At the initial ED visit, she was diagnosed with right middle lobe pneumonia and sent home on oral clindamycin. Additional laboratory test results showed an erythrocyte sedimentation rate of 70 mm/h, and a white blood cell count of 10.2×109/L, with an absolute neutrophil count of 0.51×109/L. Epstein-Barr virus titres, and blood and urine cultures were also sent and remained negative. The patient returned to the ED with persistent daily fevers (10 days total) with a maximum temperature of 38.8°C, and new-onset tachypnea and cough. Her parents denied grunting, retractions, cyanosis, vomiting, diarrhea or lethargy. Her immunizations were up to date. There was no recent travel and no known sick contacts. During the second presentation to the ED, the patient’s vital signs were a temperature of 38.8°C, heart rate of 186 beats/min, respiratory rate of 30 breaths/min, blood pressure of 141/82 mmHg and an oxygen saturation of 100% on room air. She was non-toxic in appearance and had decreased breath sounds at the right base, but an otherwise unremarkable examination. Her tachycardia resolved with administration of intravenous fluids, and her blood pressure subsequently normalized to 97/74 mmHg. A complete blood count during this second ED visit revealed a white blood cell count of 10.2×109/L with 0% neutrophils, 0% bands, 47% lymphocytes, 38% monocytes, 13% eosinophils, 0% basophils and 2% myelocytes. Her erythrocyte sedimentation rate was 65 mm/h. A chest x-ray showed minimal improvement of her pneumonia. Given her neutropenia and the lack of clinical improvement on outpatient antibiotic therapy, the patient was admitted to the hospital for further management. On admission, the patient was placed on intravenous cefotaxime. However, she remained persistently febrile, so antibiotic coverage was broadened to vancomycin and meropenem. Laboratory investigations including blood and fungal cultures, a viral respiratory panel, quantitative immunoglobulins, disseminated intravascular coagulation panel, lactate dehydrogenase, ferritin and uric acid were all unremarkable. A purified protein derivative test was negative. An abdominal ultrasound to evaluate for intra-abdominal abscess was normal. She had multiple repeat complete blood counts, which demonstrated persistent neutropenia. On her fifth day of hospitalization, the patient was able to undergo a procedure that revealed the diagnosis.