AANP Family Nurse Practitioner (FNP) Certification ExamDiagnosisHard
A 7-year-old child presents with a 2-week history of worsening right hip pain, limping, and limited range of motion, particularly internal rotation and abduction. He denies recent trauma or fever. On examination, the child is afebrile, and his right leg appears slightly shorter than the left. Which of the following conditions should be prioritized in the differential diagnosis?
- ATransient synovitis
- BSlipped capital femoral epiphysis (SCFE)
- CSeptic arthritis
- DLegg-Calvé-Perthes disease
Show answer & explanationAnswer & explanation
Correct answer: D. Legg-Calvé-Perthes disease
Legg-Calvé-Perthes disease typically affects boys aged 4-10 years, presenting with insidious onset of hip pain, limp, and limited abduction and internal rotation, often with limb length discrepancy. The absence of fever and acute trauma makes inflammatory or infectious causes less likely as the primary diagnosis.
Why the other options are wrong
- A. Transient synovitis is common in this age group but usually has a more acute onset, often post-viral, and resolves within days to a week, without limb shortening.
- B. SCFE typically occurs in pre-adolescent to adolescent obese children (10-16 years old) and is characterized by external rotation of the leg and often referred knee pain, less common in a 7-year-old without obesity.
- C. Septic arthritis would present with acute, severe pain, fever, and significant systemic signs of infection, which are absent here.
Legg-Calvé-Perthes Disease
Childhood hip disorder initiated by a temporary interruption of blood supply to the head of the femur, leading to avascular necrosis.
- Age: typically 4-10 years old (boys > girls).
- Symptoms: insidious onset of limp, hip/groin/thigh/knee pain, limited internal rotation and abduction.
- Diagnosis: X-ray shows changes in femoral head (flattening, fragmentation).
Memory trick: Perthes 'Perturbs' the hip, making it 'Persistent' and 'Painful' in younger boys.