I had a ~ 1 year old Phelsuma klemmeri female that died suddenly two months after I purchased her. Her necropsy showed that her lungs were distended and full of
Raillietiella parasites, and she probably suffocated. The strange part is that she was captive bred (of course), and that these parasites use an intermediate host (e.g., a ****roach). The breeder said he fed crickets, fruitflies, and MRP - all typical. It's a head scratcher.
The only sign that something was wrong was that she had an episode of breathing distress after egg-laying, and this resolved within a few minutes. This occurred about 2 weeks before she died.
I have no idea how rare or general this event was.
Raillietiella frenatus has been reported in
WC Phelsuma grandis on Hawaii. That species was originally described from Hemidactylus on Malaysia, and has been reported from populations of invasive Hemidactylus, suggesting that it can parasitize a wide range of vertebrate and invertebrate hosts.
(An aside: these pentastomid parasites are crustaceans, and are closely related to the
tongue-worm parasites of fish, which are super cool.)
I'm not suggesting that these parasites also caused the death of your gecko, though they could have. It's just another example of how rare things do happen. In any case, I know how much it sucks to come home to a dead gecko, so I'm sorry.
Bryan