Case Presentation: A 3 year old boy in foster care with a history of febrile seizures and speech delay presented with 2 days of fever, fatigue and difficulty walking. He complained of leg pain. On presentation, he was febrile to 102 with a heart rate of 148, a respiratory rate of 28, blood pressure of 106/69. He had an antalgic gait on exam but no joint swelling or tenderness with full range of motion of the hips and knees. Strength and sensation was intact throughout with normal reflexes. His abdomen was distended but soft and non-tender. Chemistry panel and liver function tests were normal. CBC showed anemia with a hemoglobin of 9.4 and an MCV of 76. Abdominal X-ray showed colonic distention with a large stool burden. MRI of the brain and entire spine showed a small syrinx at the T1 level. Inflammatory markers were elevated with an ESR of 101 and CRP of 25, CK was normal at 80, and LDH was elevated at 914.
Discussion: The differential diagnosis for child with a limp is broad and includes problems requiring urgent intervention to avoid significant morbidity. The most urgent concern is generally for septic arthritis, with suspicion raised in this case by fever and elevated inflammatory markers, although he had no evidence of synovitis. Osteomyelitis can present similarly, and other considerations included transient synovitis, reactive arthritis, JIA, HSP, trauma, SCFE, Legg-Calve-Perthes disease, Guillain-Barre syndrome, malignancy, and even appendicitis or other intra-abdominal infections. However, given his abdominal distention, careful review of his MRI spine showed a 5 cm retroperitoneal mass suggestive of neuroblastoma. Biopsy confirmed the diagnosis and he was transferred to the oncology service for initiation of treatment.
Neuroblastoma is the 3rd most common pediatric cancer, typically diagnosed in the first 2 years of life. It presents with intra-abdominal tumors in about 2/3rds of cases, though the tumors can arise anywhere throughout the sympathetic nervous system. In approximately 10% of cases the diagnosis is made by finding an asymptomatic abdominal mass on exam. When symptomatic, neuroblastoma can present with a wide variety of symptoms including pain, diarrhea or constipation, neurologic deficits (e.g. weakness due to cord compression), fevers, weight loss, anemia, or sympathetic symptoms such as hypertension, bladder dysfunction or Horner’s syndrome.
Conclusions: A child with a limp is a classic pediatric presentation with a differential that spans from self-resolving problems to severe illness. Malignancy of various sites, including intra-abdominal, is an important consideration on the differential, especially for patients with systemic signs or symptoms.