Symptoms of inflammatory myopathy

With dermatomyositis, especially in children, the disease begins with general manifestations, such as fever and malaise. Then there is a characteristic rash that accompanies or, more often, precedes the development of weakness of the proximal muscles. There is hyperemia of the cheeks; on the eyelids, especially the upper ones, there is a rash with a purple hue, often accompanied by edema and telangiectasias. In open areas of the skin of the chest and neck, there is an erythematous rash. The extensor surface of the knee and elbow joints is marked by discoloration and thickening of the skin. Erythematous rash is also evident in the area of interphalangeal joints on the hands. Discoloration of the nail beds is also observed, followed by the development of telangiectasia and edema. Over time, muscle weakness progresses, accompanied by pain and stiffness. The proximal muscles on the upper and lower extremities are involved to a greater extent than the distal muscles. Children with dermatomyositis may develop flexion contracture in the ankle joints.

The progression and duration of the disease are subject to significant variations. In children, dermatomyositis can proceed as an acute attack, culminating in recovery even in the absence of immunosuppressive therapy. In others, the disease acquires a remitting current with alternating exacerbations and remissions, or a progression that progresses steadily. With rapid progression, all muscles can be involved, including the larynx and pharyngeal muscles, as well as the respiratory muscles. Approximately 70% of the children in the subcutaneous tissues have calcification. Mortality in children with dermatomyositis ranges from 5 to 10%.

In adults, dermatomyositis is manifested by a rash in the area of the zygomatic arches, heliotropic discoloration and edema of the eyelids, erythema in the region of knee and elbow joints, the front surface of the neck and chest, as in dermatomyositis in children. Over time, the skin acquires a brown tint and thickens or depigmentates. Skin changes usually accompany the development of weakness in the proximal muscles or precede it. However, there have been reports of cases when the skin changes characteristic of dermatomyositis were not accompanied by muscle involvement.

Approximately 40% of adult patients with dermatomyositis have malignant neoplasm, while in patients with polymyositis, oncological diseases are detected less frequently. The clinic of a malignant tumor can outrun the symptoms of myopathy or manifest later. Removal of a tumor, for example, an ovarian tumor, can lead to regress of muscle weakness. In such cases, the threat of life itself can be represented by a malignant tumor. The true prevalence of malignant neoplasms in patients with polymoitis and dermatomyositis remains unknown, since only a small number of patients were reported in published reports, and the detection of a tumor may be ahead or behind the appearance of signs of myopathy for a year or more.

With polymyositis, the distribution of muscle weakness is the same as for dermatomyositis, but some other clinical manifestations do not coincide. Polymyositis usually develops gradually over several weeks or months, mainly involving the proximal muscles of the upper and lower extremities. Nevertheless, sometimes muscle weakness develops amazingly quickly. As a rule, the disease develops after the second decade of life, but occasionally occurs in childhood. The muscles of the eyes and mimic muscles usually remain intact. However, dysphagia is common. Typical for dermatomyositis, the rash is usually absent, but other systemic manifestations, such as arthritis, are noted in about 50% of patients with polymyositis. Disturbance of respiratory function may be caused by weakness of the respiratory muscles, aspiration pneumonia (complication of dysphagia) or interstitial pneumonitis. Involvement of the heart with a violation of the function of the conduction system, the development of cardiomyopathy and heart failure is possible both in polymyositis and dermatomyositis.

Myositis with inclusions is characterized by generalized muscle weakness. As a rule, it manifests itself in the age of over 50 years, in men more often than in women. The diagnosis of myositis with inclusions is often delayed due to the clinical similarity of myositis with inclusions and polymyositis. A distinctive feature of myositis with inclusions is the early involvement of the distal musculature of the upper limbs with the development of weakness of the flexor of the fingers and atrophy of the muscles of the forearm, as well as the involvement of the proximal and distal muscles of the lower limbs with the development of weakness of the quadriceps femoris and extensors of the foot. In one of the studies involving 21 randomly selected patients with histologically confirmed diagnosis of myositis with inclusions, the specificity of the involvement of finger flexor flexors was proved and the differential diagnostic significance of MRI was shown. In 20 out of 21 patients, a relatively specific symptom was identified - a non-uniform increase in signal intensity from the deep flexor of the fingers of the hand on T1-weighted images.

Myositis with inclusions is difficult to diagnose on the basis of only clinical data. Like polymyositis, myositis with inclusions can manifest in the second to fourth decade of life and involve the muscles of the shoulder girdle and mimic muscles. At an early stage of the disease, transient myalgias are possible. There may be clinical signs of peripheral neuropathy in the form of weakening of tendon reflexes. No connection of myositis with inclusions with oncological diseases was noted. Even with the asymmetric involvement of the finger flexor flexors and extensors of the legs, the most important clinical feature that distinguishes myositis with inclusions from dermatomyositis and polymyositis is the absence in patients with myositis with inclusions of a pronounced response to immunosuppressive therapy. Although most cases of myositis with inclusions are sporadic, family cases of the disease are described, with some clinical "overlap" with hereditary distal myodystrophies. In family cases of myositis with inclusions, the genetic defect is mapped on the 9th chromosome (9pl-ql), but the nature of the genetic defect has not yet been clarified.

[1], [2], [3], [4], [5], [6], [7], [8]