Case 1: A boy with asthma and leg pain

This case was the winner of the Trainee Clinical Case Competition at the 88th Canadian Paediatric Society Annual Conference, held in Quebec City, Quebec in June 2011 A two-year-old boy with a history of asthma presented to a community hospital with a one-week history of right leg pain that woke him from sleep, with subsequent refusal to bear weight. On physical examination, the child held his right hip in external rotation at rest. Tenderness to palpation was detected over the lower thoracic vertebrae and paraspinal muscles. He was found to have a normal range of motion in both hips and a normal gait but cried during the latter two assessments. The remainder of the examination was unremarkable. The child was admitted and, the next day, developed a fever of 39°C. A complete blood count showed a white cell count of 2.7×109/L, a hemoglobin concentration of 105 g/L and a platelet level of 205×109/L, with a normal blood smear. The erythrocyte sedimentation rate was 43 mm/h. An x-ray and ultrasound of the boy’s hips were normal. A bone scan showed innumerable foci of abnormal activity predominantly within the axial skeleton. The patient was transferred to a paediatric centre where additional bloodwork, a computed tomography scan and a magnetic resonance imaging scan were inconclusive. A bone marrow aspirate revealed only necrotic tissue. Additional investigation into the boy’s history raised suspicions that were eventually confirmed with a diagnostic procedure. Fifteen days after initial presentation, bone core biopsies obtained from the left femur showed widespread infiltration of the marrow space by cells that were consistent in appearance with lymphoblasts (36.95% blasts). Immunostaining confirmed the blasts to be early precursor B lymphoid cells. Additional investigation into the medical history by a consulting physician, who was the third physician to review the patient’s medical history, revealed the likely cause of the delay in confirming the diagnosis. Within the month before hospitalization, the patient had been treated with two courses of oral steroids for suspected asthma exacerbations that were characterized by cough. During that time, however, he was noted to experience recurrent fevers and arthralgias, and was observed to be ambulating with some discomfort. In total, the patient underwent five days of oral steroid therapy three to four weeks before his eventual diagnosis of acute lymphoblastic leukemia (ALL). ALL is the most common childhood malignancy, with approximately one-third to two-thirds of patients initially presenting with musculoskeletal pain (1). Optimal use of treatment protocols based on specific prognostic factors has led to improvements in treatment outcome, with an overall five-year survival rate of approximately 80% (2). The initial treatment phase includes administration of a glucocorticoid to help eradicate the leukemic burden and allow restoration of normal hematopoiesis. Early response to therapy, assessed by clearance of peripheral blast cells and bone marrow status, is predictive of outcome in paediatric ALL patients (3). Pretreatment with glucocorticoids before a diagnosis of leukemia has been made may lead to an adverse outcome via several mechanisms. It may hinder a diagnosis by making it more difficult to detect malignancy through conventional means, such as cell counts, peripheral blood smears and bone marrow aspirates. Steroid use also puts the child at risk of tumour lysis syndrome, which can cause acute renal failure and life-threatening electrolyte imbalances. Furthermore, due to its effects on cell lysis, improper steroid use complicates stratification of risk, dependent on the white blood cell count at presentation, thereby preventing accurate prognostication. In the present case, the use of steroids for asthma management is presumed to have masked the leukemia. Caution is required when the clinical picture does not entirely correspond with the working diagnosis, as in the present case with the diagnosis of asthma not explaining the boy’s musculoskeletal symptoms. Similarly, one should re-evaluate the situation when the appropriate treatment for the suspected diagnosis fails, as occurred when the boy received his second course of steroids. Without knowledge of the recent steroid use and its potential impact on the clinical assessment, the suspicion of malignancy may not have been as seriously considered and, thus, may have delayed diagnosis even further. Due to the inability to obtain unbiased prognostic markers and in keeping with current standard of care protocols, the patient was deemed to require more aggressive therapy and, was therefore, placed in the high-risk protocol for treatment of his leukemia. In summary, pretreatment with glucocorticoids can delay or mask the diagnosis of ALL and complicate treatment. The present case highlights the necessity of thorough history taking in ascertaining the correct diagnosis in a timely fashion, particularly when mitigating factors may obscure the clinical picture. Musculoskeletal pain is a common presenting sign in children with leukemia. Even brief courses of systemic steroid therapy can mask the clinical and laboratory features of leukemia. Atypical features of a suspected condition (ie, musculoskeletal pain in the setting of asthma) should prompt a reconsideration of the differential diagnosis.

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