Sudden death of a child associated with invasive non-typeable Haemophilus influenzae infection with underlying IgG₂ subclass deficiency

Haemophilus influenzae can be divided into typeable and non-typeable strains. Although non-typeable Haemophilus influenzae (NTHi) is less likely to be a fatal bacterium, invasive NTHi infection has been reported to increase worldwide. This study presents a case of sudden death of a child with invasive NTHi infection and underlying immunoglobulin G2 (IgG₂) deficiency. A two years seven months male child with a high fever was found unresponsive in bed, lying face down on a soft pillow. Later, the hospital declared the subject dead. An autopsy revealed that the only noteworthy finding was tissue congestion. The histopathological findings disclosed neutrophils within blood vessels of major organs. Meanwhile, the formation of the micro abscess was not visible, which indicated bacteremia. The bacterial blood culture was positive for Haemophilus Influenzae. Polymerase chain reaction assay revealed the absence of an entire capsule locus. The transmission electron microscopy showed that the colonies did not have polysaccharide capsules. Based on the above findings, the strain was identified as NTHi. Furthermore, the value of serum IgG₂ was deficient, indicating the presence of IgG₂ subclass deficiency. The subject eventually died from asphyxia by smothering due to a comorbid condition with a high fever brought on by NTHi-induced bacteremia and lying face down. IgG₂ subclass deficiency contributed to the development of invasive NTHi infection. The invasive NTHi infection might present a risk of sudden death, particularly for immunocompromised children. As forensic pathologists and pediatricians may encounter such a problematic clinical condition, they should be aware of this.