Complex sentence: In some affected individuals, Felty's syndrome may develop during a period when the symptoms and physical findings associated with rheumatoid arthritis have subsided or are not present; in this case, Felty's syndrome may remain undiagnosed.
Split into simpler sentences: In some affected individuals, Felty's syndrome may develop during a period when the symptoms and physical findings associated with rheumatoid arthritis have subsided or are not present. In this case, Felty's syndrome may remain undiagnosed.