Originally, we did not have a symptom Symptom
In medicine a symptom is what the patient complains of. For example, a a patient may have symptoms of pain and fatigue. for this problem, because as doctors we tend to think about the problem differently, as one of what we term agnosia Agnosia
An inability to identify perceptions correctly despite adequate function of the sensory organs (ears, eyes, skin, tongue, nose etc.). or apraxia Apraxia
Apraxia is defined as the inability to carry out a previously learned motor activity, despite normal function of all the component parts (muscles, nerves, joints, etc.).  For example, experiencing difficulty dressing or using a knife and fork, are often clues that apraxia is present.. But the problems occurred often enough that we realized they needed to be included on their own.

There is also evidence that links the loss of a sense of smell to a higher risk of Alzheimer's disease Alzheimer's disease
A neurological disease that affects memory and behaviour. It is characterized by beta-amyloid plaques and neurofibrillary tangles in the brain. There is no known cause but genetics and lifestyle are thought to play a role., although the most recent and best work remains preliminary. (Tabert MH, et al., A 10-item smell identification scale related to risk for Alzheimer's disease. Ann Neurol. 2005;58:155-60.)