**1. Introduction**

116 Neuromuscular Disorders

Tatara K, Shinno S (2008). Management of mechanical ventilation and prognosis in

Windisch W; Quality of life in home mechanical ventilation study group (2008). Impact of

home mechanical ventilation on health-related quality of life. *Eur Respir J.* Vol. 32,

Duchenne muscular dystrophy. *IRYO*, Vol. 62, pp 566–571.

pp 1328-1336.

Myopathy, which clinically shows muscular pain (myalgia), weakness, cramps, stiffness and spasm, is one of neuromuscular disorders due to inflammation and/or dysfunction of muscle fibers. "Myositis", which is a general term for inflammation of the muscle, is pathologically an inflammatory myopathy seen seen mainly in autoimmune disorders including dermatomyositis (DM). The myopathy is classified by National Institute of Neurological Disorders and Stroke (NINDS) as indicated in Table 1 (1). We here focus myopathy on primary Sjögren's syndrome (pSjS) associated with myalgia "mimicking DM", as previously reported (2), and the inflammatory myopathy of DM (Table 2). Most of SjS is a secondary disorder to systemic autoimmune diseases including systemic lupus erythematosus (SLE), systemic sclerosis, DM, and so on. However, SjS, which is not associated with other autoimmune diseases, is considered to be an idiopathic primary disorder characterized by sicca symptoms. It is known that pSjS may be associated with fever, fatigue, myalgia, arthralgia, cutaneous vasculitis, etc. in addition to sicca symptoms (4-8).

DM is also characterized by myalgia, muscular weakness and fatigue due to inflammatory myopathy that ultimately progresses to muscle degeneration and the cutaneous involvements. The skin manifestations include helio-trope-like colored erythema and swelling on the eye-lids, cheeks, neck and upper extremities of the sun-exposed areas and Gottron's papules on the dorsa of the hand fingers (3). Although the etiology of DM remains unknown, internal maligmant disorders including lung and/or other organ cancers are frequently associated. Generally DM is classified as shown in Table 3 (9).

<sup>\*</sup> Corresponding Author

Myopathy in Autoimmune Diseases – Primary Sjögren's Syndrome and Dermatomyositis 119

Without muscle weakness (amyopathic dermatomyositis or dermatomyositis

Overlap (myositis associated with a connective tissue disease)

Table 3. Classification of Dermatomyositis/ Polymyositis

Drake LA, et al9.: Guidelines of care of dermatomyositis. J Am Acard Dermatol 1996; 34: 824

**pSjS**: A 37-year-old woman (Case 1 in Table 2) was suffered from fever around 37.5℃, fatigue, proximal muscle pain and weakness in her limbs and arthralgia since a week before her visiting our hospital. She presented herself with swelling and helio-trope-like colored erythema on the eye-lids (Fig. 1a,b), purpurish erythema-spots on the elbows, thin-reddish erythema patches on the legs (Fig.1c) and red palms. On the dorsa of the hand-fingers, the eruption looked like Gottron's papules was seen and thin purpuric spots were also noted on the paronychial areas. The electromyography showed low amplitude motor units (less than 1 mV) from muscles of the upper extremities that were suggestive myopathy. We suspected the patient had DM and the skin biopsy was taken from the erythematous patches on the left leg. The histology revealed so-called "lymphocytic vasculitis" which showed swollen

a)

**Dermatomyosistis** 

sine myositis) With muscle weakness

 associated with cancer not associated with cancer

Inclusion-body myositis

Adult

 Pediatric **Polymyositis**  Adult Pediatric

**2. Cases** 

**Congenital myopathies**: characterized by developmental delays in motor skills; skeletal and facial abnormalities are occationally evident at birth

**Muscular dystrophies**: caused by progressive weakness in voluntary muscles; sometimes evident at birth

**Mitochondrial myopathies**: caused by genetic abnormalities in mitochondria, cellular structures that control energy; include Kearns-Sayre syndrome,

**Glycogen storage diseases of muscle**: caused by mutations in genes controlling enzymes that metabolize glycogen and glucose (blood sugar); include Pompe's, Anderson's and Cori's disease

**Myoglobulinurias**: caused by disorders in the metabolisum of a fuel (myoglobulin) necessary for muscle work; include McArdle, Tarui and DiMauro diseases

**Dermatomyositis**: an inflammatory myopathy and skin lesions

**Myositis ossificans**: characterized by bone growing in muscle tissue

**Familiar periodic paralysis**: characterized by episodes of weakness in arms and legs

**Polymyositis inclusion body myositis and related myopathies**: inflammatory myopathies of skeletal muscles

**Neuromyotonia**: characterized by alternating episodes of twiching and stiffness

**Stiff-man syndrome**: characterized by episodes of rigidity and reflex spasms

**Common muscular cramps and stiffness and tetany**: characterized by prologed spasms of the arms and legs

(National Institute of Neurological Disorders and Stroke, National Institutes of Health, USA1)


Table 1. Classification of myopathy

ALD: aldolase, ANA: anti-nuclear antibody, CK: creatine kinase, DM: dermatomyositis,

F: female, M: male, nd: not done, Nv: negative, pSjS: primary Sjögren's syndrome,

SSA: anti-SjS A antibody, SSB: anti-SjS B antibody

Myopathy: non-inflammatory myopathy, Myositis: inflammatory myopathy

Table 2. Myopathy and myositis in primary Sjögren's syndrome (pSjS) and dermatomyositis (DM)

 **Dermatomyosistis**  Without muscle weakness (amyopathic dermatomyositis or dermatomyositis sine myositis) With muscle weakness Adult associated with cancer not associated with cancer Pediatric **Polymyositis**  Adult Pediatric Inclusion-body myositis Overlap (myositis associated with a connective tissue disease)

Drake LA, et al9.: Guidelines of care of dermatomyositis. J Am Acard Dermatol 1996; 34: 824

Table 3. Classification of Dermatomyositis/ Polymyositis
