Charlotte has a severe spinal condition and is partially confined to her bed. Her husband is her full-time carer, and they have to get by on his carer’s allowance. Her impairment means they can’t share a bed. The bedroom is too small for two beds, so hers is in the second bedroom, classed as ‘spare’ under bedroom tax, and with no exemption made for their circumstances.
Source: http://figr.es/s533