Sporadic Inclusion Body Myositis Clinical Presentation

Updated: Sep 26, 2023
  • Author: Michael P Collins, MD; Chief Editor: Nicholas Lorenzo, MD, CPE, MHCM, FAAPL  more...
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Since zporadic inclusion body myositis (s-IBM) is an acquired myopathic process, weakness or impairment of muscle function in the area(s) affected is the presenting symptom. The disease follows a slowly progressive course. [2]

The distribution of weakness in s-IBM is variable, but both proximal and distal muscles are usually affected and, unlike polymyositis and dermatomyositis, asymmetry is common.

Early involvement of the knee extensors, ankle dorsiflexors, and wrist/finger flexors is characteristic of s-IBM.

Weakness of the wrist and finger flexors is often disproportionate to that of their extensor counterparts. Hence, loss of finger dexterity and grip strength may be a presenting or prominent symptom.

Dysphagia is common, occurring in 40-66% of patients with well-established disease and in 9% of patients at presentation. [72, 78] Dysphagia may manifest as a feeling of stasis, a need to swallow repeatedly, regurgitation, or choking. Mild facial weakness may be noted in about one third of patients. [79]

Isolated erector spinae weakness or "droopy neck" syndrome has been reported with s-IBM. [80]

Myalgias and cramping are relatively uncommon.

Sensory and autonomic dysfunction is not present except in patients with a concurrent polyneuropathy.

Cardiac disease is common; it is most likely due to the older age of most patients. Direct cardiac muscle involvement by the disease has not been demonstrated.



Clinical suspicion for sporadic inclusion body myositis (s-IBM) should be very high when the pattern of weakness affects (1) the finger/wrist flexors out of proportion to the finger/wrist extensors and shoulder abductors or (2) knee extensors disproportionate to the hip flexors.

Patients have variable degrees of limb weakness and atrophy, which is usually both proximal and distal, and often, but not always, asymmetric.

Facial muscle weakness may occur, but extraocular muscles are not affected and ptosis is not seen.

Tendon reflexes may be normal or decreased.

Decreased sensation in the distal lower extremities and reduced ankle jerks are not uncommon, as some patients have a concurrent polyneuropathy, which may be disease-related.

Other neurological subsystem involvement (eg, cognitive function, coordination, upper motor neuron dysfunction) is not seen in s-IBM. The presence of such findings should raise suspicion for other processes.

Examination for skin lesions, joint swelling/tenderness, and other systemic signs suggesting a concomitant autoimmune disorder should be routinely performed.

Cardiovascular examination should evaluate for hypertension, cardiac dysrhythmia/conduction abnormalities, and cardiac failure.