Case 2: A routine workup in a toddler with fever

A 16-month-old boy was brought to the emergency room with a three-week history of daily fever. The child had been experiencing a runny nose and a nocturnal cough for 10 days before coming to the hospital. No other symptoms were reported by the parents. His vaccinations were up to date. The child was born in Canada to parents who emigrated from Guinea, and had never travelled outside of Canada. His only medical history was a brief hospitalization at 12 months of age for fever related to a viral infection. There was no family history of severe or repeated infections, or of immune deficiency. At the emergency room, his rectal temperature was 38.3°C. His physical examination was negative except for a mild hyperemia of the right tympanic membrane. The initial complete blood count showed a hemoglobin level of 123 g/L and a white blood cell count of 24.9×109/L, with 14.8×109/L lymphocytes and 7.2×109/L neutrophils. The peripheral blood smear revealed the presence of Howell-Jolly bodies. The sickling screening test was negative. The chest radiograph was normal. Blood, urine and throat cultures were performed. One dose of intravenous ceftriaxone was given and a follow-up visit was planned for 24 h after discharge. All bacterial cultures remained negative. The patient received three daily doses of intravenous ceftriaxone, pending results of the cultures. Parenteral antibiotics were then discontinued. The child remained afebrile thereafter. Additional investigations revealed the diagnosis. The presence of Howell-Jolly bodies on the blood smear was confirmed by a hematologist. No spleen was found on abdominal ultrasound. A radionuclide liver-spleen scan did not show any splenic function. The patient was diagnosed with congenital asplenia. Howell-Jolly bodies refer to the small remnants of erythrocyte nuclei found in some red blood cells. Normal splenic macrophages remove particles such as bacteria, parasites and defective blood cells (eg, senescent or abnormal erythrocytes). Howell-Jolly bodies are seen, occasionally, in neonates due to splenic immaturity (1). After two months of age, the presence of Howell-Jolly bodies is abnormal and should evoke a possible diagnosis of asplenia or functional hyposplenism. The finding of Howell-Jolly bodies in a patient unknown for a condition associated with hyposplenism (eg, sickle cell disease or hereditary spherocytosis) merits additional investigations. Howell-Jolly bodies may be noted by the laboratory technician examining the patient's peripheral blood smear. When in doubt, this observation should be confirmed by a hematologist. It is the responsibility of the physician caring for the patient to recognize the importance of Howell-Jolly bodies and to request additional testing. An abdominal ultrasound is a useful first step to determine the presence or absence of a spleen. When a spleen is not identified on ultrasound, the patient can be diagnosed with asplenia and no other investigation is required. If, however, a spleen is identified, a radionuclide liver-spleen scan should be performed to determine splenic function. In the present case, asplenia was such an unexpected finding in an otherwise healthy child that a radionuclide liver-spleen scan was performed to confirm the diagnosis. Asplenia is defined as the absence of an anatomical spleen. The most common cause of asplenia in children is splenectomy. Congenital asplenia is most often seen in the context of Ivemark syndrome. This malformation syndrome consists of lateralization defects of organs in the thorax and the abdomen (or heterotaxia), and is usually associated with severe congenital heart lesions. Transmission is mainly autosomal recessive. Isolated congenital asplenia is a rare condition. A diagnosis is often made in the context of repeated infections or of severe, even fatal, bacterial infections. Isolated congenital asplenia may also be identified fortuitously in a patient with no significant medical history, as occurred in the present case (2). Familial cases are reported with an autosomal recessive or autosomal dominant transmission (3). Due to the possibility of familial or genetic transmission, first-degree relatives of a patient with congenital asplenia should be investigated with a blood smear and an abdominal ultrasound. In the present case, abdominal ultrasounds were ordered for all siblings. To date, only the two younger brothers have undergone abdominal ultrasounds and both had normal spleens. The rest of the siblings are still awaiting diagnostic ultrasounds. The spleen is the most effective filter to remove poorly opsonized bacteria, which are predominantly encapsulated organisms such as pneumococci, Haemophilus influenzae and meningococci. Patients with asplenia have a higher lifelong risk of potentially life-threatening bacterial infections than individuals with a functional spleen. The highest mortality rate is reported in children younger than two years of age. Management of asplenic patients is based on education, immunization and antibiotic prophylaxis. Penicillin prophylaxis is usually given until five years of age, but some experts continue prophylaxis throughout childhood. In our patient, prophylaxis was begun after the ceftriaxone was discontinued. His vaccinations were completed according to the immunization schedule for asplenic children. Asplenic patients and their families should receive clear instructions to urgently consult a physician at the first signs of fever or other signs of infection. Whenever possible, asplenic patients should be identified by a medical alert in the form of a wallet card, a bracelet or a letter from the treating physician. In the presence of fever in an asplenic child, parenteral antibiotics should be given promptly pending results of cultures, and hospitalization may be required depending on the clinical status of the patient. The presence of Howell-Jolly bodies on a peripheral blood smear is an important clue to a diagnosis of asplenia or splenic dysfunction. A workup for asplenia/hyposplenism should be performed in the presence of Howell-Jolly bodies after the neonatal period. The workup consists of an abdominal ultrasound, and a radionuclide liver-spleen scan if a spleen is identified on the ultrasound. Isolated congenital asplenia is a rare condition. Transmission is often familial and first-degree relatives should be screened for asplenia.

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