A 90-year-old Man With Dysphagia and Extremity Weakness

Jasvinder Chawla, MD, MBA

Disclosures

March 17, 2010

The following laboratory tests were unremarkable: blood count, electrolytes, glucose, blood urea nitrogen and creatinine, liver function, coagulation studies, thyroid function, vitamin B12, A1c, rapid plasma reagin, erythrocyte sedimentation rate, antinuclear antibody, antithyroid antibody, and angiotensin-converting enzyme.

Head computed tomography without contrast revealed minimal diffuse cortical atrophy. The patient subsequently underwent muscle biopsy from the right rectus femoris, as shown in the Figure (trichome stain). Moderate variation in fiber size is seen, with focal inflammation and degeneration with numerous nuclear bags. The trichrome-stained section showed no evidence of ragged red fibers, but there are occasional vacuoles that are very suggestive of rimmed vacuoles. Focal endomysial fibrosis is also seen. The ATPase stains at pH 4.6 and 9.4 reveal all type 1 fiber.

Figure. The trichrome stained section, with rimmed vacuoles and atrophy of the muscle fibers.

Summary

Inclusion-body myositis is a progressive inflammatory skeletal muscle disease of unknown cause and without effective treatment. Inclusion-body myositis is almost 3 times more frequent in men than in women, and the sporadic variant of inclusion-body myositis is the most common muscle disorder in patients older than 50 years. It has a slowly progressive course, with a diagnosis that is delayed by an average of 6 years after symptom onset. There is characteristic involvement of both proximal and distal muscle groups, with early involvement of the quadriceps, wrist and forearm finger flexors, and cricopharyngeal muscles.[1]

Gait abnormality may occur, with weakness involving the quadriceps and foot dorsiflexors. Hand weakness is seen in one tenth of patients, whereas dysphagia is 4 times more common than hand weakness. Myalgias are present in 40% of patients. Muscle weakness is generally symmetrical but can be asymmetrical in one third of patients. The creatine kinase level can be normal to elevated by 10-fold, and inflammatory markers are absent.

Electrophysiologic studies are important to exclude other neurogenic conditions. Some series report coexistent mild axonal neuropathy. Muscle biopsy is helpful in distinguishing inclusion-body myositis from polymyositis by the finding of characteristic microtubular filamentous inclusions on electron microscopy.[2]

Treatment is mainly supportive. It is resistant to corticosteroid and intravenous immunoglobulin treatments. Steroids are used with inclusion-body myositis associated with other connective tissue disease. Some case reports have described the usefulness of intravenous immunoglobulin.[3] However, a consensus statement from the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) ad hoc committee did not reveal any convincing support in the use of intravenous immunoglobulin in the treatment of inclusion-body myositis.[4] Most patients are confined to wheelchair within 10 years.[5]

Familial inclusion-body myositis is associated with a similar pattern of involvement of the quadriceps and long finger flexor muscles as in the sporadic variant. In addition, like the sporadic variant, familial inclusion-body myositis is associated with the DR3 and DR15 human leukocyte antigen alleles. Hengstman and colleagues[6] described difficulties with swallowing, walking, and hand dexterity in 2 sisters, aged 77 years and 66 years, who also exhibited features of sensorimotor axonal neuropathy. Hereditary forms of inclusion-body myositis have an earlier age of onset and present either with distal lower extremity weakness with relative sparing of the quadriceps (autosomal recessive form), or with a limb-girdle distribution of muscle involvement (autosomal dominant form). They are unique in that inflammation on muscle biopsy is absent.[7]

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