Haemophilus influenzae cellulitis is a skin infection caused by Haemophilus influenzae, with fever. Skin lesions mainly occur in the face of children aged below 3 years, and are characterized by a specific blue or purplish red cellulitis.


Causes

Haemophilus influenzae is a small, nonmotile, pleomorphic Gram-negative coccobacillus, divided into unencapsulated strain and encapsulated strain. Encapsulated Haemophilus influenzae is divided into six serotypes of a, b, c, d, e, and f according to the different capsular polysaccharide antigen. Most infections are caused by Haemophilus influenzae type b (Hib), and its pathogenesis is not completely understood currently. In most infections caused by Hib, there are prodromal symptoms such as upper respiratory tract infection or otitis media. Therefore, it is speculated that upper respiratory tract infection occurs, and then the bacteria invade the local skin, causing cellulitis, followed by bacteremia.

Haemophilus influenzae colonizes in the oropharynx and nasopharynx of humans as part of the normal microflora, especially in children under 5 years of age, with a normal carrier rate of up to 50%. Haemophilus influenzae is transmitted through respiratory droplets or close contact.


Signs and Symptoms

The typical skin lesions are a single, localized, poorly demarcated, bluish red or purplish red, solid plaque, surrounded by edema, mostly on the face or upper limbs. Early skin lesions can also be pale edema or erythema. Regional lymphadenopathy seldom occurs.

Cellulitis is often preceded by fever and catarrh, followed by symptoms of upper respiratory tract infection such as significant pharyngitis, otitis media, sinusitis, and epiglottitis. In the late stage, bacteremia occurs as the bacteria enter the bloodstream, resulting in metastatic infection such as septic arthritis or meningitis.


Diagnosis

This disease should be considered when infants and young children develop acute facial cellulitis with symptoms of high fever and upper respiratory tract infection. The total count of white blood cells in the laboratory test is significantly elevated. The result of bacteriological examination can assist in the definitive diagnosis.


Treatment

Most patients, including those with bacteremia, respond well to antibiotic treatment. The treatment regimen is ampicillin 150mg/kg/day intravenously. Third-generation cephalosporins, such as ceftriaxone and cefotaxime, are the first choice for the treatment of Hib infection recently, because they are effective against ampicillin-sensitive bacteria and β-lactamase-positive bacteria, and can pass through the blood brain barrier. The treatment should persist 7 to 10 days after fever drops.


Prevention

Early immunization with Hib conjugate vaccine can significantly reduce the nasopharyngeal carrier rate and enhance the immunity, leading to an overall decline in the incidence of invasive infection. In families with children under 4 years of age, first episode in parents and susceptible children who have not received vaccination should be treated with rifampicin to eliminate nasal bacteria and prevent secondary infection.