A 4-year-old boy with a history of asthma is brought to the ED by his mother with cough, fever, and increasing lethargy over the past three days. He was given albuterol for his cough without improvement, and had posttussive emesis on one occasion. His mother denied stool changes. He attends daycare but has no sick contacts or pets at home.
His vital signs are notable for a temperature of 38.3°C, tachypnea to 45, and a heart rate of 160 bpm. He is normotensive, and you hear decreased breath sounds on the left. His abdominal exam is benign, but he has trace edema of his ankles bilaterally and fine petechiae where a tourniquet was placed.
His portable chest radiograph is shown and demonstrates a left multilobar pneumonia with a large, loculated pleural effusion. His laboratory results are significant for a white blood count of 11.7, platelets of 12, hemoglobin of 5.7, a BUN of 49, and a creatinine of 1.2. A peripheral smear shows helmet cells.
The patient is started on broad-spectrum antibiotics and placed on bi-level positive pressure ventilation. What should you do next? Does the patient warrant blood products at this time?
Find the diagnosis and case discussion on the next page.
Diagnosis: Atypical Hemolytic-Uremic Syndrome
Hemolytic-uremic syndrome (HUS) is characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. It primarily affects children under 5, with an annual incidence of 6.1 cases per 100,000 children. (New Engl J Med 2009;361:1676.) HUS has classically been divided into diarrhea-positive (typical HUS) and diarrhea-negative (atypical HUS) subtypes.
Typical HUS is associated with Shiga toxin-producing Escherichia coli (STEC) diarrhea, and accounts for 90 percent of all HUS cases in children. Atypical HUS — the diagnosis in this case — can be triggered by Streptococcus pneumoniae, complement dysregulation, medications, or a variety of viral infections. Atypical HUS has a mortality up to 25 percent, and nearly half will progress to end-stage renal disease. (J Am Soc Nephrol 2005;16:1035.)
Treatment is focused on supportive care. Adequate intravenous fluids are crucial. Packed red blood cells should be transfused for symptomatic anemia, but platelets should be withheld unless major bleeding is present. Dialysis is warranted for symptomatic uremia, volume overload, and electrolyte derangements. Other therapies can be tailored to the cause of HUS. Antibiotics are traditionally not given for STEC-related HUS because of concerns of bacterial lysis causing worsening toxin release, but appropriate antibiotics should be started for streptococcal-associated atypical HUS.
Therapies such as steroids, plasmapheresis, and intravenous immunoglobulin have failed to demonstrate consistent benefit for HUS. (Eur J Pediatr 2010;169:7.) There is mounting evidence for the use of an anti-C5 monoclonal antibody — eculizumab — for atypical HUS triggered by inherited or acquired complement dysregulation. (Pediatr Nephrol 2016;31:15.)
The patient was admitted to the pediatric intensive care unit (PICU) and had chest tube drainage of the empyema, which was sent for S. pneumoniae antigen confirmation. He was placed on a renal diet with sufficient intravenous rehydration and with nephrology following closely to initiate dialysis if needed. His glomerular filtration rate hit a nadir of 22 and then returned to baseline without the need for renal replacement therapy. He required one packed red blood cell transfusion for symptomatic anemia but did not receive any platelets. His pneumonia steadily improved on antibiotics. He was discharged home on room air without restrictions after a week in the PICU.
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