Fever and Limp

• Core 1 (Pre-clerkship)
  • Microbiology and Infectious Disease 1, Week 2: Antibiotics
  • Microbiology and Infectious Disease 1, Week 4: Infectious Arthritis
• Core 2 (Clerkship)
  • Pediatrics Clerkship didactics on Acutely ill
• Core 3 (Post Clerskhip) Electives that may further your knowledge
  • Peds ID, Peds Orthopedics

Clinical Vignette: A 3-year-old presents with 3 days of fever and limping (favoring left leg), now with refusal to bear weight on the left leg. His mother denies any falls or recent known trauma.  

History:

• Discuss any known trauma or possibility of unidentified trauma (was child alone with another caregiver such as at daycare?) 
• Recent symptoms suggestive of viral illness: cough, rhinorrhea, vomiting, diarrhea
• B-symptoms: fever, unexplained weight loss, night sweats
• Exposures: recent travel, exposure to animals, tick bites/exposure to outdoors in Lyme endemic areas
• Dietary history: does the child eat foods containing adequate vitamin C and vitamin D (concern for scurvy, rickets)?
• Developmental history – when did the child start walking, have they had prior difficulty with gait? 

Physical Exam:

• Assess gait as able
• Assess back for tenderness or deformities
• Assess extremities: look for point tenderness over bones, joint swelling, range of motion, be sure to assess all joints of the lower extremity (hip, knee, ankle) 
• Assess for lymphadenopathy
• Assess for any rashes
• Assess abdomen: palpate for mass, tenderness, hepatosplenomegaly
• Assess GU: testicular torsion (referred pain → limp)
• Assess neurological exam

The differential for limping in a pediatric patient is quite broad. Below are multiple ways to organize the differential. In the setting of limp + fever, consider the underlined diagnoses 

STOP LIMPING mnemonic: 

• Septic arthritis (hip or knee) 

• Toddler’s fracture 

• Osteomyelitis 

• Perthes disease (Legg-Calve-Perthe disease) 

• Limb length discrepancy 

• Inflammatory (transient synovitis, juvenile idiopathic arthritis, reactive arthritis) 

• Malignancy 

• Pyomyositis 

• Iliopsoas abscess 

• Neurologic (stroke, ataxia) 

• Gastrointestinal/GU (appendicitis, ovarian torsion, testicular torsion) 

VITAMIN BCD (more expansive differential diagnosis for limp): 

• Vascular: stroke, Legg-Calve-Perthes disease, avascular necrosis (such as in Sickle Cell disease) 

• Infectious/Inflammatory: Septic arthritis, transient synovitis, osteomyelitis, Lyme arthritis, pyomyositis, iliopsoas abscess (such as in IBD), rheumatic fever, reactive arthritis 

• Traumatic: Accidental or non-accidental trauma, toddler’s fracture 

• Autoimmune: Juvenile idiopathic arthritis, reactive arthritis, acute rheumatic fever 

• Metabolic: Scurvy, Ricket’s 

• Iatrogenic/Idiopathic: Slipped capital-femoral epiphysis 

• Neoplastic: bone tumors (Ewing sarcoma, osteosarcoma), leukemia, lymphoma 

• Behavioral: diagnosis of exclusion 

• Congenital: Developmental dysplasia of the hip, cerebral palsy 

• Degenerative: less pertinent in pediatric population 

Evaluation

Below are some tests that you may consider; use your history and physical exam to create an initial differential diagnosis to guide which tests to prioritize 

Most Patients 

Labs

• Complete Blood Count (CBC) for infectious and some oncologic etiologies
• Comprehensive Metabolic Panel (CMP)
• C- Reactive Protein (CRP) > Erythrocyte Sedimentation Rate (ESR)
• Creatine Kinase (CK), if concern for myositis
• Lyme testing, if rash or exposure history
• Blood culture 

Imaging 

• XR to assess for fracture or deformity, rule out primary bony oncologic diagnoses
• US joint to assess for effusion
• MRI joint to assess for effusion, osteomyelitis, myositis 

If concerned for malignancy 

• LDH, uric acid (if concerned for malignancy) 

If concerned for inflammatory etiology 

• UA (assess for urethritis in reactive arthritis – need non-catheterized specimen)
• Respiratory viral testing (transient synovitis)
• ANA panel (only if high suspicion for rheumatologic disorder)
• Anti-streptolysin O antibody, anti-DNAse B antibody (acute rheumatic fever)
• Stool cultures (reactive arthritis) 

If history of restrictive diet 

• Vitamin C level (scurvy)
• Vitamin D level (rickets) 

If effusion is identified 

• Synovial fluid studies – Cell counts, differential, culture, gram stain, Kingella PCR if < 5 years of age
• WBC > 50,000
  • Concerning for septic arthritis
  • High percentage of PMNs
  • Positive gram stain or culture 

• WBC 25,000-50,000 

• • Equivocal
  • Consider Lyme arthritis or gonococcal arthritis 

• WBC <25,000 

• • Transient synovitis 

• Kocher Criteria: helpful to distinguish septic arthritis from transient synovitis.
  • MD Calc: Kocher Criteria 

Management of Common Causes of Pediatric Fever and Limp 

• Transient synovitis 

• • Temporary inflammation of the lining of a joint space called the synovium thought to be related to immune response, often to viruses.
  • Will often see bilateral effusions on hip US, differentiating this from septic arthritis which is typically unilateral.
  • Typically self-resolves over a course of weeks.
  • Recommend supportive care including NSAIDs and heat or ice packs for comfort. 

• Osteomyelitis 

• • Common Pathogens: Staph aureus, Strep pyogenes, Kingella kingae (in children < 5 years) 

• • Imaging 

• • Treatment: Initiate empiric antimicrobials 

• • • Cefazolin versus clindamycin if MRSA risk factors
    • Narrow antimicrobials as tolerated based on culture data (if available) and transition to oral regimen if able
    • Treatment duration varies based on clinical response and pathogen 

• Septic arthritis 

• • Treatment: empiric antimicrobials
    • Cefazolin versus clindamycin if MRSA risk factors
    • Target pathogens: Staph aureus, Strep pyogenes, Kingella kingae (in children < 5 years)
    • If synovial fluid culture positive for gram negative organism: ceftriaxone
    • Narrow antimicrobials as tolerated based on culture data (if available) and transition to oral regimen if able
    • Treatment duration varies based on clinical response and pathogen 

• Limping in a pediatric patient has a very broad differential diagnosis, so it is important to have a framework to sort through the different categories of diagnoses and identify red flag diagnoses to rule out.
• History and physical exams are essential to narrowing down this broad differential diagnosis and guiding further consultation and workup.
• Understand the Kocher criteria for diagnosis of septic arthritis.
• Understand the interpretation of synovial fluid studies.  

Answers

Q1: Ultrasound of left hip to evaluate for effusion

Q2: Juvenile Idiopathic Arthritis 

• Articles
  • The Limping Child | Pediatrics In Review | American Academy of Pediatrics  (Access through biomedical library for full article)
• Pathway
  • Septic Arthritis Clinical Pathway — Emergency Department | Children's Hospital of Philadelphia 
  • Osteomyelitis Clinical Pathway — Emergency Department and Inpatient | Children's Hospital of Philadelphia 
• Other Resources
  • Kocher Criteria for Septic Arthritis