Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
These changes may require a review of support rather than emergency treatment.
Call emergency services for:
A seizure lasting five minutes or longer
Repeated seizures without recovery between them
Severe breathing difficulty or blue or grey lips
Choking with inability to breathe or respond
Sudden unresponsiveness
Follow any individual emergency or seizure plan already provided.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek urgent medical advice for a first suspected seizure, a sudden decline in swallowing, signs of dehydration, or new breathing symptoms.
3
Does any of this apply?
Book an appointment
Arrange a routine medical assessment if you notice unexplained loss of developmental skills, increasing weakness, unusual startle responses, repeated falls, balance problems, or changes in speech.
These symptoms have many possible causes and do not mean someone has Tay-Sachs.
The article also says
If Tay-Sachs has already been diagnosed, contact the care team about changes such as coughing during meals, weight loss, more frequent seizures, increasing stiffness, pain, sleep problems, or repeated chest infections.
Every sign above is quoted from the sofidex article on Tay-sachs disease. If you are not sure, err upward — it is always reasonable to be checked.