Anne Maree Lee, 29, was sentenced on February 27 to nine years in jail and must serve at least a third before she can be released on parole.

She was jailed for manslaughter after lying her way out of taking responsibility for her toddler or simply ignoring his existence until he died in a Caboolture home.

Ms Lee failed to get Mason medical treatment after her partner, 37-year-old William Andrew O'Sullivan, ruptured her son's stomach in 2016.

O'Sullivan was handed a nine-year sentence in the Brisbane Supreme Court last year for manslaughter and child cruelty.

A spokeswoman for Attorney-General Yvette D'Ath said on Wednesday an appeal had been lodged.

"Attorney-General Yvette D’Ath will appeal the sentence handed down to Mason Jet Lee’s mother, Anne Maree Lee, for manslaughter and child cruelty," the statement read.

"Mrs D’Ath requested the appeal after receiving legal advice from the Director of Public Prosecutions.

"Lee received a head sentence of nine years, with parole eligibility after three years.

"No further comments will be made as this matter is before the court."

A coronial inquest into Mason's death was announced last month after deputy state coroner John Lock had been investigating the circumstances surrounding Mason's death.

The inquest will open at a later date this year.

Mason spent the last of his days vomiting, feverish and dehydrated because O'Sullivan failed to get him treatment after hitting or kicking him in the abdomen in response to him crying.

He had lived much of his 22 months in pain, suffering from a broken leg and severe injuries before the fatal blow five days before he died in agony.

O'Sullivan had taken Mason in because he did not believe Ms Lee was capable of caring for him.

A dermatologist who treated Mason said it was the worst case he had seen in his 40 years' experience.