On the one hand we behold a constitutional disease with widespread manifestations—a special joint inflammation, which tends neither to the deposit of urate of soda nor to suppuration; a peculiar acid secretion from the skin; highly acid urine; a notable tendency to inflammatory heart complications; marked pyrexia. We observe also a marked disposition to recurrence and to the hereditary transmission of the diathesis.
The phenomena of rheumatism may be ill defined; that is to say, the attack may be subacute, but the features are the same; or they may linger and assume the chronic form, in which fever is replaced by a peculiar alteration in the fluids of the body, showing itself in a dull anæmic complexion and a greasy skin; but in all cases the seat of the disease-signs is in the joints; it is articular.
On the other hand, myalgia is not a general malady nor the expression of one. It is scarcely a disease at all. It is purely local. A muscle or a group of muscles, overworked, cry out, and this cry is interpreted by the sensation of pain. It is to be borne in mind that the overwork may be absolute, or merely relative to the healthfulness of the muscle at the time. In either case there is a derangement between the balance of work and nutrition in the muscle. The secretions are not altered; there is no sweating; the urine presents no abnormal conditions. Endo- and pericarditis never occur as complications; fever is absent.
The attack is often light, and quickly passes away. If it become chronic, further nutritive changes take place. The muscle becomes rigid, and often atrophies. According to Froriep and Virchow, as quoted by Jaccoud2 and Niemeyer,3 the fasciculi are beset here and there with thickened connective tissue. Vogel observed in several chronic cases the neurilemma of the nerves supplying the part to be thickened, hardened, and adherent.
2 Traité de Pathologie interne, Paris, 1871.
3 Lehrbuch der Speciellen Pathologie und Therapie, Berlin, 1871.
In all cases the affection limits itself to the muscles. The joints remain free. When they undergo changes it is after a long time and as a result of want of use or of reflex disturbances of nutrition through the nervous system. Nothing is known of hereditary predisposition to myalgia. In the manifest tendency to recur in the same individual it and rheumatism are alike. In all essential points their clinical resemblance is of the most superficial kind. It is clear, then, that the processes which give rise to the phenomena of rheumatism do not directly affect the muscular system.
The credit of having first formulated this opinion, previously only vaguely recognized, is due to Roche and Cruveilhier,4 but Valleix, Garrod, Flint, and other writers, who describe myalgia under the head of muscular rheumatism, coincide in this view. Even the statement that the two diseases are constantly associated is not borne out by the results of extended clinical inquiries. My own observation has not confirmed it. Of 7 cases5 taken at random to illustrate a point of treatment, 1 had followed an attack of rheumatic fever; 1 occurred in an individual who had many years before suffered from rheumatism; and 5 gave no history whatever of that disease: 1 followed tonsillitis. DaCosta6 details 2 cases of myalgia—1 in the loins (lumbago), associated with bronchitis or following it, the other occurring during an attack of rheumatic fever and having its seat in the muscles of the neck. In the latter case the constitutional disease yielded to treatment which had no effect upon the local malady. Even were the association much more frequent than it is found to be, the fact would by no means establish a common causation, seeing that myalgia follows other diseases which impair the nutrition of the body. It is worthy of note that the groups of muscles most frequently involved in cases which happen during or after acute diseases are those which must work perforce—those which maintain the equilibrium of the body or carry on respiration, etc. Hence we see wry neck, lumbago, pleurodynia associated with other diseases; affections of the muscles of the extremities after overwork pure and simple.
4 Dict. de Méd. et de Chir. prat., article "Arthrite."
5 Philada. Med. Times, Nov. 7, 1874.