**2. Description and clinical features of Duchenne**

Typically, DMD patients are clinically normal at birth, although serum levels of muscle isoform of creatine kinase are elevated. The onset of pseudohypertrophy of the calf muscles, proximal limb muscle weakness suggests DMD. Weakness of the arms occurs later along with progres‐ sive kyphoscoliosis (Dubowitz. Major Probl Clin Pediatr 1978).

Most patients die in their early twenties as a result of respiratory complications due to intercostal muscle weakness and respiratory infection. Death can also be the result of cardiac dysfunction with cardiomyopathy. BMD and DMD patients also present with mild cognitive impairment, indicating that brain function is also abnormal in these disorders (Blak and Martin-Rendon, 2002).

Fetal DMD is histologically normal except for occasional eosinophilic hypercontracted fibers (Bertorini et al. 1984). Necrotic or degenerating muscle fibers are seen in all postnatal DMD muscle biopsies even before muscle weakness is clinically seen. The necrotic fibers are phagocytized, and muscle biopsies from DMD patients reveal the presence of inflammatory cells at perimysial and endomysiel sites (Arahata and Engel 1984). The regenerative capacity of the muscle is lost and muscle fibers are gradually replaced by adipose and fibrous connective tissue, giving rise to the clinical appearance of pseudohypertrophy followed by atrophy (Emery 1993), resulting in muscle wasting and ultimately muscle weakness (Blake et al 2002). Most patients die in their early twenties as a result of respiratory complications due to intercostal muscle weakness and respiratory infection. Death can also be the result of cardiac dysfunction with cardiomyopathy. BMD and DMD patients also present with mild cognitive impairment, indicating that brain function is also abnormal in these disorders (Blake and Kroger 2000).

DMD muscle shows signs of oxidative damage (Murphy and Kehrer 1989). Muscle diseases in which oxidative damage may play a primary role show features in common with DMD (Mendell Et al 1971). Moreover, muscle cells from mdx mice have an increased susceptibility to oxidative stress (Rando et al 1998). The lack of neuronal-type nitric oxide synthase (nNOS) seen in DMD causes disregulation of vascular tone, and ischemia (Crosbie 2001, Blake et al 2002). This henomenon may increase the generation of free radicals. Open follow-up trials with antioxidants are indicating positive clinical response (Gebre-Medhin et al 1985; Timber 1989; Westermarck et al 1997).

A low blood selenium level has previously been observed in healthy inhabitants of Finland (WESTERMARCK, 1977). In this study even lower blood selenium values were observed in patients with acrodermatitis enteropathica, dystrophia musculorum progressiva (Duchenne), infantile and juvenile type of neuronal ceroid lipofuscinosis (NCL), severe mental retardation caused by various factors, and myocardial infarction. The selenium content of the brain, heart, kidney and liver in patients of different ages was also determined. The highest selenium level was found in the kidney. The mean liver selenium concentrations in stillborn, premature and full-term neonates were 1.11 +/- 0.23 (8), 1.21 +/- 0.17 (12) and 0.93 +/- 0.16 microgram/g dry weight (12) respectively (the number of subjects in parentheses). The selenium values are considerably higher than those in infants of from one to nine months of age and adults, whose liver selenium values were 0.58 +/- 0.21 (8) and 0.67 +/- 0.08 microgram/g dry weight (8) respectively. The vitamin E levels of serum in patients with NCL, as well as in subjects with severe mental retardation (controls), were low compared with values in healthy normal subjects. Sodium selenite supplementation in patients with NCL produced at least a transitory improvement without causing any toxic effects during one year of administration. In Duch‐ enne muscular dystrophy we found that 75Se-selenite was not absorbed in the lower extremities in the equal level compared to healthy ones.
