Christine Assange said her son has had only brief moments of sunlight since entering the Ecuadorian embassy in June 2012 and his body is feeling the effects.
"His body is breaking down to such an extent that he now has heart problems, a chronic lung infection (and) deep and severe shoulder pain," she told ABC radio on Friday.
"His doctor has ordered an MRI and one hour of sunlight a day and the UK government has refused."
Ms Assange also said the UK and Swedish governments had lied and spread misinformation about her son's case.
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"They've lied to the media and that's one of the biggest problems in this case: the amount of misinformation put out there," she said.
Ms Assange cited the example of Swedish prosecutors refusing to interview her son in the UK, despite doing so for 44 witnesses and suspects since 2010.
