How did Edgar Allan Poe's foster mother die?

Poe's foster mother, Frances Keeling Valentine Allan, died of consumption (tuberculosis) on February 28, 1829. Frances Allan carried on with life but remained devoted to her foster son until she died. Poe never had an adopted mother nor step mother.

We honestly cannot be certain what caused the death of Frances Keeling Valentine Allan. The local newspaper called it a "lingering and painful" illness. She had been sickly even when they lived in England, and she could likely have had a similar condition even before the Allans took Poe in. Definitely, the most likely candidate is consumption, or tuberculosis. She died while Poe was in the US Army, and he was not able to return home until the day after her funeral.

Frances Allan died of tuberculosis in 1829.