A 17-year-old boy comes to the office due to leg pain in his left thigh for over a year. He first noticed the pain only while running, but it became more frequent and more intense even after walking short distances. For the last 3 weeks, the pain has occurred even while sitting down or lying in bed. He has taken acetaminophen and ibuprofen with no relief. The patient has a history of sickle cell disease and has previously been hospitalized for back, chest, and leg pain, but he says that the current pain is different. Three weeks ago, he had an upper respiratory illness that lasted for 3 days and resolved spontaneously. He does not use tobacco, alcohol, or illicit drugs. Temperature is 36.7 C (98 F), blood pressure is 110/70 mm Hg, and pulse is 78/min. Height and weight are at the 10th percentile for age. Physical examination demonstrates an alert, uncomfortable adolescent. There is pain on flexion, extension, and rotation of the left hip, with restricted range of motion. Distal pulses and deep tendon reflexes are normal. Gait is notable for a slight limp. Complete blood count shows normocytic anemia with a normal white blood cell count. Which of the following would most likely explain this patient's symptoms?

Question

A 17-year-old boy comes to the office due to leg pain in his left thigh for over a year.  He first noticed the pain only while running, but it became more frequent and more intense even after walking short distances.  For the last 3 weeks, the pain has occurred even while sitting down or lying in bed.  He has taken acetaminophen and ibuprofen with no relief.  The patient has a history of sickle cell disease and has previously been hospitalized for back, chest, and leg pain, but he says that the current pain is different.  Three weeks ago, he had an upper respiratory illness that lasted for 3 days and resolved spontaneously.  He does not use tobacco, alcohol, or illicit drugs.  Temperature is 36.7 C (98 F), blood pressure is 110/70 mm Hg, and pulse is 78/min.  Height and weight are at the 10th percentile for age.  Physical examination demonstrates an alert, uncomfortable adolescent.  There is pain on flexion, extension, and rotation of the left hip, with restricted range of motion.  Distal pulses and deep tendon reflexes are normal.  Gait is notable for a slight limp.  Complete blood count shows normocytic anemia with a normal white blood cell count.  Which of the following would most likely explain this patient's symptoms?

Quizplus · Accepted Answer

11ec25c8_d276_f1de_bc81_abb0449c3071_MD0003_00 This patient most likely has osteonecrosis, or avascular necrosis, of the left hip due to sickle cell disease (SCD). Osteonecrosis is a common complication of SCD secondary to red blood cell sickling, microinfarctions, and bone hyperplasia. The most common sites are the humeral and femoral heads. Clinical features typically include chronic groin, buttock, or thigh pain that initially occurs with weight bearing but progresses to occurring at rest. Examination demonstrates pain and limited range of motion with internal rotation and abduction of the hip. Because it is a chronic, noninflammatory process, avascular necrosis does not present with erythema or warmth of the joints, leukocytosis, or elevated inflammatory markers. X-rays of the hip may appear normal early in disease, and MRI should be performed to confirm the diagnosis. (Choice A) Splenic dysfunction in patients with SCD predisposes them to infections with encapsulated organisms (eg, Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis). Given this patient's chronic pain, lack of fever, and normal white blood cell count, septic arthritis is very unlikely. (Choice B) Slipped capital femoral epiphysis (SCFE) results in displacement of the proximal femur due to external shearing forces (eg, obesity, trauma). Patients with SCFE typically report hip or groin pain with weight bearing. Because SCFE relies on an open growth plate, it is more common in younger adolescents than in those of this patient's age. Slipped capital femoral epiphysis (SCFE) (Choice C) Femoral neck fractures can predispose to avascular necrosis as they may disrupt vascular flow to the femoral head. These fractures, however, typically occur in older adults and are associated with known trauma. Given the chronic nature of pain without preceding trauma, SCD is a more likely cause of avascular necrosis for this patient. (Choice D) Osteosarcoma is a malignancy that typically presents in adolescents with subacute or chronic lower extremity pain. Osteosarcoma typically involves the distal femur or proximal tibia, however, and patients with SCD are not at higher risk of osteosarcoma than the general population. (Choice F) Reactive arthritis presents with asymmetric arthritis most commonly in the lower extremities after a preceding gastrointestinal infection or genitourinary infection. The chronic nature of this patient's pain and preceding respiratory illness make reactive arthritis unlikely. Educational objective: Osteonecrosis, or avascular necrosis, is a common complication of sickle cell disease. Patients typically report chronic groin, thigh, or buttock pain without warmth or erythema of the joints, leukocytosis, or elevated inflammatory markers. References: Avascular necrosis of the femoral head in sickle cell disease patients. (http://www.ncbi.nlm.nih.gov/pubmed/22619100)

A 17-Year-Old Boy Comes to the Office Due to Leg