Read this excerpt from the patient's discharge summary:
HPI:
Decker Macmillan is an 8-year-old boy admitted directly to the pediatric floor for workup of chronic progressive hypotonia. His parents report they have noticed progressive weakness. Decker has had increasing difficulty running, jumping, and climbing stairs. His parents initially thought his problems were due to his asthma, but they noticed that he also had a waddling gait. They took him to their primary care provider, who referred him for evaluation. On admission, Decker denied any history of myalgia, arthrodynia, or dystaxia. His problem appeared to be limited to muscle tone.
According to this information, which of the following is part of the history of the present illness?
a) poor coordination
b) muscle pain
c) joint pain
d) decrease in muscle tone or tightness