Why would hearing happy birthday provoke such anxiety? The answer is quite simple. The attention that goes with the singing as well as the expectation to blow out candles and make a wish is a behavioral nightmare to someone with FXS. The problem is that every time the song is sung, the memory of being overwhelmed by all the attention becomes reenacted. As is often the case, the gestalt or wholeness of the experience becomes so solidified that it is very hard to convince the person with FXS that it will not make him anxious the next time it happens. As a matter of fact, it is difficult to convince the person with FXS that even when the song is sung to someone else, it does not need to affect him. Parents mention that the anticipation of a birthday party for another family member can also be intense and the family learns to excludes the song during subsequent celebrations.
This is a naturalistic impetus for hyperarousal. The easiest remedy is not to sing Happy Birthday and to make the celebration less overwhelming overall. But when the song is sung in a public environment, take the I-pad or I-phone out and wire it up to headsets. This will buffer the sound. If the person with FXS does not tolerate headsets or ear buds, just district him with a video or game on an electronic device. Using a social story can also be of help especially if it is read before going to a party or having one.