Pediatric Fever and Leg Pain
Journal of Emergency Medicine
Volume 34, Issue 1, January 2008, Pages 79-81
Authors: Sara W. Nelson MD, David F.M. Brown MD, and Eric S. Nadel MD
Case Presentation
Dr. Sara Nelson: Today’s case is that of a 5-year-old boy who presented to the Emergency Department (ED) with complaint of bilateral leg pain for 10 days. He described the pain as involving his knees through his ankles. The pain was sharp and occurred intermittently throughout the day. The pain was worse in the afternoons and with running and jumping. The boy’s parents had noticed that he was walking with a slow, shuffling gate. There was no history of trauma, leg swelling, or joint instability. According to his parents, the patient was a healthy boy with normal growth and development. He had never been hospitalized, took no medications, and was allergic only to peanuts. Immunizations were up to date. There was no relevant family history. Review of systems was notable for 6 weeks of fatigue and a fever on the day before presentation. He saw his pediatrician, who noted some bilateral hip tenderness. Plain radiographs of the hips and pelvis were obtained. These were normal and he was referred to the ED.
On initial examination, vitals signs were: temperature 37.3°C, pulse 122 beats/min, blood pressure 114/49 mm Hg, respiratory rate 22 breaths/min, and oxygen saturation 100% on room air. He was a well-nourished boy in no distress. Examination of the head revealed reactive round symmetric pupils, anicteric sclerae, and moist mucous membranes. The oropharynx was clear without erythema or exudates. The neck was supple with slightly enlarged cervical lymph nodes. The lungs were clear to auscultation bilaterally. Heart sounds were regular, with no murmurs. The abdomen was soft, non-tender, and non-distended. The liver edge was palpable 2 cm below the right costal margin. There was no splenomegaly or other masses. The scrotum and testes were normal and without masses. There was inguinal and axillary lymphadenopathy bilaterally. There was no swelling, erythema, or point tenderness of the extremities. Joint examination was normal with full passive range of motion of the hips, knees, and ankles. There was no joint laxity. The back was non-tender. Neurological examination was notable for a slow, somewhat shuffling gait but was otherwise normal.
Dr. David Brown: Are there any thoughts as to the initial differential diagnosis
Dr. Eric Nadel: We have a child with leg pain and gait disturbance and a question of fever. The differential diagnosis at this point is rather broad. Infectious causes of leg pain include septic arthritis, osteomyelitis, myositis, and discitis of the intervetebral discs. Septic arthritis is a serious diagnosis that cannot be missed as it can cause rapid joint destruction. History of fever, non-weight bearing, erythrocyte sedimentation rate > 40 mm/h, and a serum white blood cell count of > 12,000 cells per cubic millimeter are strong clinical indicators of septic arthritis of the hip (1). Inflammatory causes of limp and leg pain include transient synovitis, juvenile rheumatoid arthritis, and lupus. Neuromuscular causes of leg pain include muscular dystrophy, peripheral neuro-pathy, and reflex sympathetic dystrophy. Musculoskeletal injury is, of course, a common cause of leg pain; often there may be no history of overt trauma. Stress fractures can occur with repetitive loading activities in children and occur most often in the tibia, fibula, pars intrarticularis, and femur (2). Toddler’s fractures occur in the distal third of the tibia in children between 9 and 36 months of age and occur after trivial injuries (3). And, of course, child abuse should always be a consideration when dealing with any pediatric injury.
Dr. Daniel Pallin: Another category of leg pain and limp is bony deformity. Bilateral developmental dysplasia of the hip can present as a lordotic, swaying limp in older children, whereas unilateral developmental dysplasia of the hip is often picked up during infant screening or when a toddler starts to walk (4). Slipped capital femoral epiphysis, in which the femoral epiphysis slips posteriorly, occurs most often in obese children in early adolescence (5). Legg-Calvé-Perthes is an idiopathic avascular necrosis of the hip and usually presents as a painless limp in children 2 to 12 years old (6). Another common cause of leg pain in children, especially active adolescents, is Osgood-Schlatter disease, which is an over-use syndrome that leads to osteochondritis and apophysitis of the tibial tuberosity at the insertion of the patellar tendon (7).
Dr. Nelson: We considered all of these categories of leg pain when evaluating this patient. The history and physical examination were notable for subacute onset of symptoms, normal musculoskeletal examination, and associated symptoms of fever and fatigue. Given these symptoms, tumor and malignancy were also part of our initial differential diagnosis. Osteoid sarcoma is a benign tumor of children and adolescents that can present with a limp and with leg pain, especially at night. The femur is the most commonly affected bone (8). The two most common malignant bone tumors in children are osteogenic sarcoma and Ewing’s sarcoma (9). Common sites for these tumors are the distal femur, proximal tibia, and humerus. Ewing’s sarcoma can also affect the axial skeleton (10). Finally, 20–30% of children with acute leukemia may present with bone and joint pain (11). The pain often involves the long bones and is due to leukemic infiltration of the periosteum. The presence of generalized lymphadenopathy in our patient made us particularly concerned about this diagnosis.
Dr. Ben White: How did you proceed with the work-up
Dr. Nelson: Given these diagnostic considerations, our initial work-up in the ED included a complete blood count with differential, serum electrolytes and liver function tests, urinalysis, chest radiograph, and cultures of the blood. The results of the complete blood count (CBC) sharply defined the differential diagnosis, as the white blood cell count was 6.29 K/mm3 with 10% neutrophils and 31% lymphoblasts. The hematocrit was 27.7% and the platelet count was 104 K/mm3. Results of the other laboratory testing were as follows: sodium 133 mEq/L, potassium 4.5 mEq/L, chloride 98 mEq/L, bicarbonate 23 mEq/L, BUN 21 mEq/L, creatinine 0.5 mEq/L, and glucose 100 mEq/L. Calcium was 10.2 mEq/L, magnesium was 2.2 mEq/L, and phosphate 5.5 mEq/L. Liver function tests revealed AST 130 mEq/L, ALT 99 mEq/L, alkaline phosphatase 201 mEq/L, total bilirubin 0.3 mEq/L, uric acid 3.7 mEq/L, and lactate dehydrogenase (LDH) 1297 mEq/L. The urinalysis was normal. The chest radiograph revealed no infiltrates or masses.
Dr. Nadel: The CBC is highly suggestive of acute leukemia, given the anemia, thrombocytopenia, borderline neutropenia, and blast predominance in the white cell differential. What additional evaluation was performed in the ED
Dr. Nelson: A peripheral blood smear was prepared and oncology was consulted. During the ED course, the patient developed a fever to 39.0°C and was empirically started on cefepime for his relative neutropenia (640 cells/mm3). He was admitted to the pediatric oncology service with the presumptive diagnosis of acute lymphocytic leukemia.
Dr. J. Tobias Nagurney: The leukemias are the most common malignant neoplasm in children, accounting for about 30% of all malignancies in children < 15 years of age (12). It is important to consider this diagnosis in the ED, especially when children present with persistent, non-specific symptoms. Acute lymphocytic leukemia (ALL), which is a disorder of T- or B-cell progenitor cells (or lymphoblasts), is about five times more common than acute myeloid leukemia, which is a disorder of myeloblasts (13). The presentation of ALL in children is varied. Common symptoms include musculoskeletal pain, lymphadenopathy, headache, mediastinal mass (seen most commonly in adolescent males with T-cell ALL), testicular enlargement, fever, bleeding, fatigue and, of course, peripheral blood abnormalities.
Dr. Jennifer Millen: What are the peripheral blood abnormalities that are seen in ALL and how is the definitive diagnosis made
Dr. Nelson: Acute leukemia leads to bone marrow failure. As a result, anemia or thrombocytopenia will be seen in most patients (14). The white blood cell count can vary, with about half of patients having initial leukocyte counts of < 10,000/mm3 and 20% having a leukocyte count of > 50,000/mm3 (15). Lymphocytes may be initially reported as “atypical,” but further examination of the peripheral smear will reveal > 25% lymphoblasts (14). Bone marrow aspirate or biopsy will confirm the diagnosis of ALL and should be performed whenever the peripheral blood suggests the possibility of leukemia.
Dr. Ruth Lamm: Were you concerned about tumor lysis syndrome in your patient
Dr. Nelson: Tumor lysis syndrome is a metabolic derangement that is caused by the rapid release of intracellular contents when leukemic or cancerous cells are destroyed. Typically, tumor lysis syndrome occurs 1–5 days after the initiation of chemotherapy, but can occur before starting treatment (16). As should be done in every new diagnosis of leukemia, we ordered blood tests from the ED to screen for tumor lysis syndrome. In particular, we evaluated for hyperuricemia, hyperphosphatemia, hypocalcemia, and hyperkalemia. We screened for acute renal failure that can be caused by the deposition of uric acid crystals in the renal tubules. In our patient, each of these tests was normal and so we felt tumor lysis syndrome was unlikely. The LDH was elevated at 1297 mEq/L. Uric acid and LDH levels correlate with the total tumor burden and the risk of developing tumor lysis syndrome (16). To prevent tumor lysis syndrome, patients should be given two times maintenance intravenous fluids without potassium. In addition, sodium bicarbonate can be administered to alkalanize the urine (pH 7.5–8), which enhances phosphate and uric acid secretion. Allopurinol also can be given to prevent or correct hypocalcemia.
Dr. Alison Lozner: What was this patient’s hospital course
Dr. Nelson: Flow cytometry testing was consistent with pre-B cell ALL. On the next hospital day, a bone marrow biopsy confirmed the diagnosis. Subsequent evaluation included cerebrospinal fluid cytology, ophthalmology examination, and echocardiogram, all of which were normal. The patient was started on induction chemotherapy and a tumor lysis protocol was initiated with intravenous fluids, urine alkanalization, and allopurinol. He was treated with cefepime and vancomycin for continued fevers although his blood and urine cultures remained negative throughout his hospital stay. He received multiple blood transfusions for his anemia. The patient was discharged on hospital day number 25. A repeat bone marrow biopsy on day number 32 of the chemotherapy protocol confirmed remission; consolidation therapy was subsequently begun. The patient returned to school after being out for 3 months and, according to his most recent oncology clinic notes, is still in remission and doing well.
Dr. Brown: This case raises some interesting and important points. First, as was stated earlier, the differential diagnosis of leg pain and limp in a child is very broad and should always include malignancy, especially when the child has persistent and unexplained symptoms. The second point is that leukemia is the most common form of malignancy in children and early diagnosis can greatly improve outcome. The initial cancer and tumor lysis work-up should start in the ED. The ED evaluation should include: a CBC with differential; tumor lysis syndrome laboratory tests including uric acid, LDH, basic metabolic panel, phosphate and calcium; liver function tests, coagulation studies, fibrinogen and D-dimer to assess for disseminated intravascular coagulation; urinalysis, urine cultures, and blood cultures if there is evidence of infection; baseline viral titers to look for other causes of atypical lymphocytes; and a chest radiograph to look for a mediastinal mass (most common in T-cell ALL). A testicular ultrasound is indicated if the testes are enlarged and a lumbar puncture should be performed before the initiation of treatment to assess for central nervous system involvement, but these tests can generally be done on the in-patient service. ED treatment should be aimed at tumor lysis syndrome or infection if either is suspected.
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