What viruses can cause orthopedic abnormalities in the lower extremities in young children?

Viruses Associated with Orthopedic Abnormalities in Lower Extremities of Young Children

Several viral infections can cause orthopedic abnormalities in the lower extremities of young children, with enteroviruses being the most significant causative agents, particularly enterovirus-71 (EV-A71) and enterovirus-D68 (EV-D68), which can lead to acute flaccid myelitis and paralysis affecting the lower limbs. 1

Enteroviruses

• Enteroviruses are the most common viral cause of orthopedic abnormalities in the lower extremities of young children, particularly through neurological manifestations that affect motor function 1
• Enterovirus-71 (EV-A71) can cause hand, foot and mouth disease with rare but severe cases of rhomboencephalitis that may lead to neurogenic pulmonary edema and fatal cardiorespiratory collapse, as well as acute flaccid myelitis (AFM) affecting limb function 1
• Enterovirus-D68 (EV-D68) has been associated with severe respiratory disease and acute flaccid myelitis (AFM), causing rapid limb weakness with low muscle tone and changes in the gray matter of the spinal cord visible on MRI 1
• AFM presents with clinical signs of rapid limb weakness and low muscle tone, with MRI showing changes in the gray matter of the spinal cord 1

Human Parechoviruses

• Human parechoviruses (HPeVs), particularly HPeV3, can cause severe disease in young infants including meningoencephalitis and sepsis-like presentations that may affect neurological function and potentially lead to lower extremity abnormalities 2
• HPeV infections can manifest as meningoencephalitis, seizures, or sepsis-like presentations that may have adverse neurodevelopmental outcomes affecting motor function 2
• Young infants with HPeV typically present with fever, irritability, and sometimes a diffuse rash (described as "red, hot and angry" babies) 2

Influenza Viruses

• Influenza viruses, particularly Influenza A and B, can be associated with neurological disorders including encephalitis and acute necrotizing encephalopathy (ANE) 1
• Influenza B can cause severe myositis in conjunction with acute necrotizing encephalopathy, potentially affecting lower extremity function 1
• The H1N1 strain of Influenza A has been reported to cause more neurological manifestations than seasonal flu, including encephalopathy, focal neurological signs, and aphasia 1

Other Viral Causes

• Rotavirus can cause encephalopathy with convulsions and cerebellar signs in some children, potentially affecting gait and lower extremity function 1
• Measles virus can cause three separate encephalitic illnesses that may affect neurological function and motor control 1

Clinical Presentation and Diagnosis

• Children with viral-induced orthopedic abnormalities may present with:
  • Rapid limb weakness and low muscle tone 1
  • Gait abnormalities secondary to neurological involvement 1
  • Disability or deformity in the lower extremities 1
• Diagnosis requires:
  • Respiratory and stool samples in addition to cerebrospinal fluid (CSF) and blood samples for viral testing 1
  • Reverse transcriptase PCR (RT-PCR) targeting the 5′noncoding regions (5′NCR) for diagnosis of enteroviruses 1
  • VP1 capsid protein gene sequencing for enterovirus typing 1

Management Considerations

• Most viral-induced orthopedic abnormalities require supportive care as there are no specific antiviral therapies for many of these infections 2
• Children with disability, deformity, or gait abnormality secondary to viral neurological conditions should be referred to a pediatric orthopedic surgeon 1
• Follow-up by a pediatrician is recommended for infants with severe viral infections that may have adverse neurodevelopmental outcomes 2

Important Caveats

• Viral detection in CSF may be challenging, particularly for viruses like EV-D68 which are rarely detectable in CSF or stool samples 1
• The peak incidence of most enteric viral illnesses is in children under 2 years of age, making this age group particularly vulnerable 3
• Viral-induced orthopedic abnormalities may be misdiagnosed as other conditions, so a high index of suspicion is needed in children presenting with acute onset of lower extremity weakness or abnormalities 1