Leyden Type of Dystrophy

LEYDEN TYPE OF DYSTROPHIES (Leyden) (also known as the Leyden-Möbius type of progressive muscular dystrophy), identified in the 1870s by Leyden as an independent form differing, on the one hand, from the spinal form of Duchenne-Aran, and on the other, from pseudohypertrophies. At the present time, it is regarded as one of the forms of progressive muscular dystrophy. At one time, this form was called hereditary because, in describing this specific form, Leyden first drew attention to the hereditary origin of such diseases. As with pseudohypertrophic forms, the disease here also begins in the proximal sections of the lower extremities and the sacrum, but unlike the former, it is not accompanied by false or true muscle hypertrophies. Most of these cases begin in childhood (8–10 years). The disease develops, like other forms of muscular dystrophies, insidiously in children who were previously completely healthy. The atrophic process spreads symmetrically. The altered "waddling" gait, resulting from atrophy of the gluteal muscles, strikes the eye first. Such children fall easily and climb stairs with difficulty. Typical for them is the manner of rising from a horizontal position, indicating weakness of the extensors of the back, thighs, and lower legs. The lordosis observed in these cases also belongs to the early symptoms of the disease. The shoulder girdle and upper extremities are affected much later. Here, atrophy also begins with the proximal sections. In later periods, atrophy can also spread to the face. The electrical excitability of the muscles presents only a quantitative decrease. There are no fibrillary twitches. Tendon reflexes decrease in parallel with the decrease in strength of the-atrophying muscles. No special deviations are noted on the part of the nervous system. The psyche often presents various degrees of congenital inferiority, which usually does not progress with the development of the muscular process. The disease develops very slowly, and new muscle groups are only gradually involved. Long periods of arrest of the process (up to 10 years and more) are noted. Pathologically and anatomically, the condition involves changes in the muscles themselves, having the same character as in other forms of muscular dystrophies. The lighter coloration of the muscles is striking. Microscopically, one finds inequality in the caliber of individual muscle fibers; alongside sharply thickened ones, strongly thinned ones are located. In addition, splitting of fibers along their length, vacuolization, proliferation of sarcolemma nuclei, and an increase in fibrous and fatty tissues in the perimysium are noted. Transverse striation is preserved even in strongly altered muscles. Recently, many authors have considered a disorder of the vegetative, particularly the sympathetic, nervous system to be the cause of the disease. The disease is of a hereditary-familial nature. Sporadic cases are also observed. The type of inheritance cannot be considered definitively established. Recently, some authors (Davidenkov, Bing) have spoken in favor of a dominant, partially sex-linked type of inheritance. Duchenne's pseudohypertrophy (differing from the Leyden-Möbius form by an earlier onset) and Erb's juvenile form (differing by a later onset) are inherited in the exact same way. Therefore, the opinion has been expressed that the Leyden-Möbius form may not be an independent disease, but represents an artificial composite group encompassing atypically late-onset cases of pseudohypertrophy or atypically early-onset cases of the juvenile form. For therapy, see Dystrophy.