Son has one big toe nail that has fallen off & the other big toe nail is lifting. No trauma, fungus ruled out, nail flat/spoon, ideas of cause?

I will provide an . Idea, it is a little difficult without seeing the actual foot. I do believe that fungus and trauma are the most common causes. Trauma does not have to mean a heavy object fell on the toe. Repetitive micro trauma like a toe hitting the end of a shoe when running etc could be a cause, and nails can be negative for fungus due to false negatives.
See below. Onycholysis is the separation of the nail plate from the nail bed. It can be caused by local problems like periungual warts or fungus (onychomycosis), but the most common reason for separation is trauma. However, some systemic diseases can cause this like psoriasis and hyperthyroidism. Have your pediatrician look into these possibilities.

Related Questions

My 20 mth sons big toenail fell off & his other big toe is lifting from nailbed. No trauma, fungus ruled out, nails are flat/spoon. Ideas on causes?

See below. Onycholysis is the separation of the nail plate from the nail bed. It can be caused by local problems like periungual warts or fungus (onychomycosis), but the most common reason for separation is trauma. However, some systemic diseases can cause this like psoriasis and hyperthyroidism. Have your pediatrician look into these possibilities. Read more...
Spoon shaped nails. Spooned shaped nails are associated with anemia. Not sure if he has had blood work done but maybe the pediatrician can have blood work done to rule this out. Also make sure his shoes are not too tight as this could also cause detachment of the nail. Read more...
Trauma. Can be from shoes - take all his shoes with you and see derm or podiatrist. Read more...
Toenail. Technical term is onycholysis and usually falls off or lifts from nail bed due to trauma. Spoon shape could be a systemic problem like anemia. Read more...