What is the role of rash and seizures in narrowing the differential diagnoses of Haemophilus influenzae type b (Hib) meningitis?

Updated: Jul 09, 2018
  • Author: Prateek Lohia, MD, MHA; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Rashes are much more commonly associated with such differential considerations as Neisseria meningitidis meningitis, Rocky Mountain spotted fever, subacute bacterial endocarditis, and viral (eg, echovirus 9) meningoencephalitis than with Haemophilus influenzae type b (Hib) meningitis. In these diseases, the rash is typically erythematous and macular or maculopapular at onset and may quickly progress to petechia and purpura. Note that rashes of this sort are occasionally observed in Hib encephalitis.

Hemiconvulsive seizures at presentation with low-grade fever may necessitate the exclusion of Hashimoto encephalopathy. Focal or hemiconvulsive seizures in children may suggest such alternative diagnoses as herpes I, LaCrosse, Japanese B, or other forms of encephalitis, depending on time of year, region of the world, and historical exposures.

Most children younger than 18 months who present with a history of fever and seizures but who have normal findings on examination (including reliable exclusion of meningismus) do not have meningitis. One study showed that the risk for meningitis in such infants is approximately 1.2%. Of the 4 children in that study who did have meningitis, 3 had viral and 1 had Hib meningitis. Children older than 18 months who present with a history of fever and a seizure but who have normal examination findings are even less likely to have meningitis.

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