Pediatric Haemophilus Influenzae Infection Clinical Presentation

The history is targeted to identifying the specific Haemophilus influenzae disease syndromes, which include the following:

• Meningitis

  • Prior to H influenzae type B (Hib) vaccines, meningitis was the most common and serious manifestation of invasive disease.
  • Disease is insidious in onset, with a preceding nonspecific febrile illness. No specific etiologic clues are present. The signs and symptoms can be nonspecific.
  • Young infants may present with irritability, lethargy, anorexia, or vomiting. Only older children are likely to present with the classic findings of headache, photophobia, and meningismus. Therefore, the absence of meningismus is not a helpful finding for excluding meningitis in a young child.
• Epiglottitis

  • Acute upper airway obstruction caused by Hib infection of the epiglottis and supraglottic tissues is perhaps the most dramatic and rapidly progressive form of disease caused by H influenzae.
  • Epiglottitis primarily occurs in older children (aged 2-7 y), and it usually has an abrupt onset with high fever, dysphagia, drooling, and toxicity.
  • Occasional cases of Hib epiglottitis in older children still occur in children who were never fully immunized.
  • Hib is also an important cause of epiglottitis in adult patients.
• Septic arthritis and osteomyelitis: In the prevaccine era, Hib was the leading cause of septic arthritis in children younger than 2 years.
• Cellulitis

  • Hib cellulitis usually involves the face, head, or neck.
  • Most cases occur in children aged 2 years or younger.
• Occult bacteremia: In the prevaccine era, Hib was the second leading cause of occult bacteremia after Streptococcus pneumoniae.
• Pneumonia: Hib pneumonia caused as many as one third of the documented cases of bacterial pneumonia in the prevaccine era.
• Pericarditis
• Neonatal disease

  • In recent years, H influenzae has been increasingly recognized as a cause of bacteremia and meningitis in neonates. Neonatal infections are usually caused by nontypeable H influenzae, which can be cultured with samples from the maternal genital tract, the presumed source of the infection.
  • The disease involves early-onset sepsis;^[4] more than 80% of cases occur in 1-day-old neonates.
  • Maternal-to-fetal transmission probably occurs in utero because the infection is associated with prematurity, low birth weight, and maternal complications such as premature rupture of membranes and chorioamnionitis.
• Brazilian purpuric fever

  • A nonserotypeable H influenzae biogroup III (identical to the H aegyptius group) organism has been demonstrated to be the cause of a disease called Brazilian purpuric fever (BPF) discovered in children in southern Brazil.
  • After an antecedent episode of purulent conjunctivitis, children with BPF become bacteremic and present with fever, shock, and purpura fulminans.
  • The disease may mimic meningococcemia, but this has not been reported in the United States.
• Nontypeable H influenzae disease

  • Underlying medical conditions, such as prematurity, cerebrospinal fluid (CSF) leak, congenital heart disease, and immunoglobulin deficiency, may predispose an individual to invasive disease caused by the nontypeable strains of H influenzae.
  • Immunization with conjugate Hib vaccines does not confer protection against the nontypeable strains. Therefore, nontypeable H influenzae remains a major cause of otitis media in children. (Other common causes of acute otitis media in children are S pneumoniae and Moraxella catarrhalis.) Hib is an unusual cause of acute otitis media, particularly in the era of conjugate vaccines.
  • Occasionally, the encapsulated non-Hib strains of H influenzae are implicated as causes of invasive disease.
  • Recent findings from a series of H influenzae type f meningitis cases suggest that these organisms conceivably could emerge as important causes of invasive disease in children in the post-Hib vaccine era, although this trend has not yet become widespread.

Physical examination findings depend on the clinical syndrome. Because Hib is primarily a bacteremic infection, comprehensive physical examination and complete evaluation are mandatory, with a focus on excluding meningeal, lung, and pericardial involvement.

At physical examination, findings may include the following:

• Meningitis

  • Approximately 30% of children have seizures at some point in the course of Hib meningitis.
  • Like patients with meningococcal disease, children with Hib bacteremia can have a petechial rash.
  • Patients can also have a secondary site of infection, such as septic arthritis or facial cellulitis.
  • Shock is present in approximately 20% of patients.
  • Anemia is common; it is caused by a combination of accelerated RBC destruction and diminished erythropoiesis.
  • Complications of Hib meningitis include subdural effusion or empyema, ischemic or hemorrhagic cortical infarction, cerebritis, ventriculitis, intracerebral abscess, and hydrocephalus.
• Epiglottitis

  • Typically, a child with Hib epiglottitis drools because of an inability to swallow the oropharyngeal secretions, and progressive respiratory distress develops over a period of hours, with tachypnea, stridor, cyanosis, and retractions.
  • The patient may sit forward with his or her chin extended, in the so-called tripod position, to maintain an open airway. Few conditions produce such a striking constellation of symptoms and findings.
  • Lateral neck radiography can be helpful if the clinical presentation is subtle (see Imaging Studies), but diagnostic studies should not delay direct inspection of the epiglottis in the operating room and insertion of an endotracheal tube. The mortality rate of 5-10% is invariably related to poor early airway control.
• Septic arthritis and osteomyelitis

  • These usually affect the large joints, particularly knees, ankles, hips, and elbows.
  • Contiguous osteomyelitis may be present, but isolated osteomyelitis without an adjacent septic joint is uncommon.
  • Characteristically, preceding nonspecific illness is present; this is followed by pain, swelling, and erythema of the involved joint.
  • Clinical signs in children with a septic hip may be less prominent than in those with other affected joints. Findings may be limited to a decreased range of motion in the joint or referred pain from the hip.
  • A strong association exists between septic arthritis and meningitis; lumbar puncture is necessary.
• Cellulitis

  • Buccal cellulitis occurs almost exclusively in infants aged 1 year or younger. In infants, the onset of illness includes fever and a raised, warm, tender, and indurated area that develops a violaceous hue.
  • The clinical presentation may mimic erysipelas.
  • Periorbital (preseptal) cellulitis occurs in young children, and it often occurs in the context of contiguous sinus disease. It must be differentiated from the more serious orbital (postseptal) cellulitis, which can be a life-threatening complication of invasive Hib disease (or disease caused by other pathogens).
  • Often a complication of disease in the paranasal sinuses, orbital cellulitis can lead to cranial sequelae, including cavernous sinus thrombosis. (Typically, hospital admission for intravenous antibiotics, imaging studies [CT scan, MRI], and consultations with an ophthalmologist and a neurosurgeon is required.)
  • The clinical triad of chemosis, proptosis, and ophthalmoplegia should prompt consideration of the diagnosis of postseptal cellulitis.
  • Hib cellulitis is a bacteremic disease, and meningitis must be excluded by means of lumbar puncture.
• Occult bacteremia

  • Although most children with Hib bacteremia have a focus of infection, occasionally bacteremia can be the sole manifestation of disease in the febrile child. These children are usually younger than 2 years and have temperatures of 39°C or higher.
  • An important distinction between Hib and pneumococcal bacteremia is that most episodes of untreated occult pneumococcal bacteremia resolve spontaneously without sequelae, whereas 30-50% of children with occult Hib bacteremia have focal infections, including meningitis. Hence, in any child with blood culture results positive for Hib, the possibility of meningitis must be seriously considered.
• Pneumonia

  • Hib pneumonia is clinically indistinguishable from other bacterial pneumonias. It has a strong association with pleural effusion; therefore, radiography may be helpful (see Imaging Studies).
  • The best diagnostic test is blood culture, which has positive findings in almost 90% of patients.
  • Complications of Hib pneumonia include pleural empyema, pericarditis, and meningitis.
• Pericarditis

  • The classic presentation of H influenzae pericarditis is that of a toxic-appearing child with fever, respiratory distress, and a clear chest on examination.
  • Associated conditions include pneumonia and meningitis.
  • Hib pericarditis may become clinically apparent when a child receives antibiotic therapy. It should be considered in the differential diagnosis in a child who has a persistent fever while receiving therapy for Hib meningitis.
  • Although the diagnosis may be suggested after careful inspection of the cardiac silhouette and neck veins, echocardiography is the best test for establishing the diagnosis of pericardial effusion.
  • Pericardiocentesis is the diagnostic procedure of choice.
• Other invasive infections

  • Hib bacteremic disease is rarely associated with seeding of other body sites.
  • Endophthalmitis, glossitis, uvulitis, thyroiditis, endocarditis, lung abscess, epididymitis, peritonitis, intraperitoneal abscesses, hepatobiliary disease, and brain abscesses have been reported.
• Nontypeable H influenzae disease

  • Nontypeable strains of H influenzae frequently cause otitis media, sinusitis, conjunctivitis, and bronchitis. Conjunctivitis is usually bilateral and purulent and often occurs in association with acute otitis media (ie, conjunctivitis-otitis syndrome).
  • Although these respiratory tract infections are common, they are rarely life threatening. In general, they are not associated with bacteremia.
  • The finding of nontypeable H influenzae systemic infection should prompt immunologic investigation, even if the obvious risk factors are absent.
• CNS involvement: The CNS is a major target organ in invasive H influenzae disease.
• Cardiovascular involvement

  • Children with invasive Hib disease often have septic shock.
  • Cardiovascular instability may manifest as blood pressure instability.
  • Myocardial dysfunction may occur, and pericarditis is a known and important complication.
• Respiratory involvement

  • Invasive Hib disease may cause pneumonia or upper airway obstruction secondary to epiglottitis.
  • Clinicians skilled at airway management should be available to coordinate the treatment of these children.
• Fluid and electrolyte disturbances: When meningitis is present, children may have disturbances in fluid and electrolyte homeostasis due to shock and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).