Question: why might it be difficult for medical professionals to diagnose a specific illness

title: Medical diagnosis
text: Diagnosis is often challenging , because many signs and symptoms are nonspecific . For example , redness of the skin ( erythema ) , by itself , is a sign of many disorders and thus does not tell the healthcare professional what is wrong . Thus differential diagnosis , in which several possible explanations are compared and contrasted , must be performed . This involves the correlation of various pieces of information followed by the recognition and differentiation of patterns . Occasionally the process is made easy by a sign or symptom ( or a group of several ) that is pathognomonic . 

Answer: answer: Diagnosis is often challenging, because many signs and symptoms are nonspecific. Thus differential diagnosis, in which several possible explanations are compared and contrasted, must be performed. This involves the correlation of various pieces of information followed by the recognition and differentiation of patterns. Occasionally the process is made easy by a sign or symptom that is pathognomonic.
answer: Diagnosis is often challenging , because many signs and symptoms are nonspecific .