Complex sentence: Many CFS patients will also have, or appear to have, other medical problems or related diagnoses comorbid fibromyalgia occurs in a large percentage of CFS patients between onset and the second year, and some researchers suggest fibromyalgia and CFS are related.
Split into simpler sentences: Many CFS patients will also have, or appear to have, other medical problems or related diagnoses comorbid fibromyalgia is common. Fibromyalgia occurs in a large percentage of CFS patients between onset and the second year, and some researchers suggest fibromyalgia and CFS are related.