Annie's acrocyanosis appeared long before there was any decline in her breathing. It wasn't the result of CO2 buildup. It was simply caused by the inability of her leg muscles to help circulation in her lower legs and feet. The result was an accumulation of fluids in her lower extremities. She was getting normal blood-gas exchange, it just wasn't getting properly circulated in her lower extremities.
Because it appeared in the absence of widespread ALS effects none of her doctors identified it with ALS. When it began she was only having trouble with her left lower leg, notably foot-drop. The color ranged from raspberry reddish to purplish. As she weakened it became more pronounced until it reached a steady-state, i.e., it didn't get any worse. It then developed in her other leg as it became weakened by the ALS. This discoloration was pretty much confined to her ankles and feet. The swelling extended upward to include a little bit of the extreme end of her lower legs, but that too was predominately in her ankles and feet.
Once her disease had progressed to the point of diagnosis, then her doctors readily identified the discoloration as a consequence of her ALS caused leg muscle weakness. In retrospect I don't know why, coupled with her obvious lower leg muscle atrophy, it didn't cause some of the doctors to at least start investigating the possibility of ALS. My conclusion is that most doctors think in terms of their past experience and automatically try to fit the current patient's presentation into that body of past experience. That's why you'll find so many on this forum who strongly recommend that patients seek out doctors, especially neurologists, who specialize in ALS - they have a much better experience base with ALS and are more likely to be able to make more accurate and quicker assessments.
