Diminished distal dorsal finger wrinkling in patients with sporadic inclusion body myositis

Sporadic Inclusion Body Myositis (IBM) is the most common acquired myopathy after the age of 45. Often there is a delay in diagnosis as the disease may be mistaken for other inflammatory myopathies and other neuromuscular disorders such as motor neuron disease. One of the hallmarks of the disease is distal finger flexor weakness but non-neurologists who see IBM may not have the expertise to make this assessment. Other clinical signs that require less expertise may be of value in identifying this disorder. We present three cases of patients with IBM who had loss of wrinkling of the dorsal distal interphalangeal joints of the fingers that was not seen in any control patients who had no finger flexor weakness. The loss of wrinkling of the dorsal distal interphalangeal joints of the fingers is an additional physical exam finding that could distinguish IBM from other neuromuscular disorders.