Waxy Degeneration

WAXY DEGENERATION, or glassy, or Zenker's (after the author who first described it) degeneration of muscles; in most modern guides to pathological anatomy, it is treated as muscle necrosis and is described in the chapter on necrosis. Nevertheless, the name W.D. is firmly retained for this process to the present time. The reason for this duality is apparently that the basic changes observed here, although irreversible (in nature approaching the category of coagulative necroses), however, affect only the contractile substance of the muscle fiber, completely sparing neither the sarcolemma nor the nuclei with surrounding sarcoplasm. The process [see separate table (Vol. IV, p. 351-352), Fig. 3] begins with swelling of the contractile substance and its transformation into a homogeneous, hyaline-like, opaque mass, which at the same time, as it were, cracks in the transverse direction. The longitudinal striation completely disappears at this time; the transverse one is initially still barely distinguishable in the form of very dense and fine striation (obtained, it is thought, as a result of very sharp contraction of the corresponding area), but then it also disappears, and all the fibrillar content of the fiber breaks down into a series of separate clumps or masses of different sizes. Since the diameter of these masses often exceeds the cross-section of the adjacent part of the fiber, the sarcolemma in their location stretches, while in the intervals between them, on the contrary, it collapses, whereby the corresponding part of the fiber may acquire an irregularly wedge-shaped appearance. Subsequently, on the one hand, the breakdown of the formed masses into smaller parts with their gradual liquefaction and resorption occurs, on the other hand, regenerative growth of muscle nuclei, as well as the surrounding sarcoplasm. The latter, under favorable conditions, leads to the formation of large multinucleated plasma masses, which merge with the remnants of undamaged contractile substance and subsequently differentiate into contractile fibrils. Thus, the integrity of the muscle fiber can be restored. The reparative process described occurs the more frequently and successfully the smaller part of the fiber was affected and the weaker the damage to the surrounding tissue (inflammatory changes, hemorrhages, etc.). Otherwise, the entire fiber dies as a whole and is replaced by connective tissue. The size of the affected area of muscles can be extremely varied: from individual fibers found only under the microscope to extensive foci occupying a significant part of the muscle. To the naked eye, such foci appear, compared to healthy muscle tissue, swollen, cloudy, pale, resembling wax or fish meat. They tear easily not only under the hands on the dissecting table, but often during the patient's life due to sharp contraction of the affected muscle, which usually leads to more or less extensive hemorrhages. In this latter case, the entire focus acquires the appearance of a hematoma. W.D. is observed in striated muscles both of the skeleton and of the heart. For the former, the classic site of localization of the process is the m. rectus abdominis, the most frequent etiological factor being typhoid fever. In addition, W.D. can be seen very often in the diaphragm muscles, oblique muscles of the abdomen, adductor muscles of the thigh, and in the tongue (less frequently in other muscle groups), with prolonged or intense tension of these muscles apparently being a contributing factor. As for etiology, in addition to typhoid fever, various other infections and poisonings (relapsing fever, tetanus, diphtheria, smallpox, epidemic cerebrospinal meningitis, trichinosis, poisoning with snake venom, etc.), as well as many other harmful influences such as trauma (rupture, crushing, etc.), circulatory disorders (ischemia, stasis), burns, frostbite, the action of electric current, etc., may play a role here. In the heart muscle, W.D. most often occurs as one of the components of the histological picture of acute myocarditis in severe diphtheria (less frequently with other infections) and is sometimes designated as granular degeneration (schollige Degeneration). The decay masses formed here are mostly much finer and smaller than in skeletal muscles; however, the usual outcome of the process is apparently the death of the corresponding area of the muscle fiber and its replacement by connective tissue. Similar W.D. changes have been described by Beneke in smooth muscle fibers as well.