Regular pattern of fever (periodic), approximately three-weekly, perhaps associated with malaise, periodontitis, aphthous ulceration, impetigo, sore throat and enlarged lymph glands.
But by the time the child presents, the neutrophil count may have returned to normal (although unlikely to be high).
Check FBC twice weekly for 4-6 weeks to demonstrate the fluctuation of the neutrophil (and monocyte) count.
Important not to miss, as children can develop severe bacterial sepsis while neutropaenic (mortality rate of up to 10%).
Need antimicrobial prophylaxis, and possibly GCSF.
Differential is PFAPA (periodic fever, aphthous stomatitis, pharyngitis, adenitis)