Complex sentence: The traditional term covers such a range of different problems that to ascribe symptoms to "rheumatism" is not to say very much: arthritis and rheumatism between them cover at least 200 different conditions.
Split into simpler sentences: The traditional term covers such a range of different problems that to ascribe symptoms to "rheumatism" is not to say very much. Furthermore, arthritis and rheumatism between them cover at least 200 different conditions.