Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services for trouble breathing, a seizure lasting several minutes or repeated seizures, fainting, severe confusion, uncontrolled bleeding, blue or gray lips, or difficulty waking the person.
Contact the care team promptly for a new fever, worsening cough, painful skin redness, pus or drainage, unusual bruising, repeated nosebleeds, increasing weakness, new balance problems, or a major change in energy.
Fever thresholds and response plans should follow the person’s specialist instructions.
Seek urgent medical assessment for persistent fever with marked tiredness, abdominal swelling, jaundice, rapidly increasing bruising, or a sudden decline in health.
These symptoms can occur during the accelerated phase but may have other causes.
Routine follow-up should be planned with the immunology, hematology, transplant, genetics, eye, and neurology teams as appropriate.
Visits may include blood counts, liver tests, infection review, bleeding assessment, vision checks, and evaluation of movement, strength, sensation, learning, or memory.
The article also says
Families should have a written plan explaining whom to call for fever, infection symptoms, bleeding, or possible HLH.
Instructions may be different during immune-suppressing treatment or after transplantation.
Every sign above is quoted from the sofidex article on Chediak-higashi syndrome. If you are not sure, err upward — it is always reasonable to be checked.