A perfectly happy life has been put on hold by a mysterious, debilitating disease that has left doctors here and overseas searching for a diagnosis for more than a year. It’s a “one in a zillion” nightmare, and this couple’s reality. Fernando Rezende Silveira, 44, and Fernanda De Almeida Santos Cordeiro, 42, are birds of a feather. They fell in love on a salsa dance floor in Brazil 20 years ago and later moved to the Northern Beaches, where they now own an apartment in Brookvale and a dog named after the Latin art form that brought them together. These days the dancing has stopped as has many of Fernando’s motor skills. Fifteen months ago he began losing vision and mobility, struggling to swallow and showing...