symptoms began as difficulty with buttoning his shirt and
using keys to open doors about 2 years ago. He was
treated empirically with nonsteroidal anti-inflammatory
medications for arthritis, but responded only minimally.
His symptoms have slowly progressed to the point where
he has weakness in both hands and feet. He avoids going
outside because of frequent falls. On examination, he has
weakness and atrophy of the foot extensor and finger flexors.
Proximal muscle strength is normal. Reflexes are normal,
and sensation is intact. He is able to rise out of a
chair, but the Romberg test is not able to be performed
due to weakness once standing. Cranial nerves are intact.
Serum creatine kinase is 600 U/L. Complete blood count,
differential, electrolytes, and thyroid-stimulating hormone
(TSH) are normal. Based on the clinical presentation,
what is the most likely diagnosis?
A. Dermatomyositis
B. Eosinophilic myofasciitis
C. Inclusion body myositis
D. Polymyositis
E. Hyperthyroidism
The answer is C. Inclusion body myositis. The inflammatory myopathies (polymyositis, dermatomyositis, and inclusion body myositis) are associated with unique clinical features. Inclusion body myositis is usually seen in patients ≥50 years and initially involves the distal muscles, especially the foot extensors and finger flexors. Atrophy is seen along with weakness as this inflammatory myopathy runs a slowly progressive course, compared to polymyositis or dermatomyositis. Polymyositis is a rare disorder that usually involves the
ReplyDeleteproximal not distal muscles. It is a diagnosis of exclusion after a thorough medical examination and muscle biopsy. Dermatomyositis is distinguished by the classic heliotrope
rash and associated skin findings, which may precede the development of clinical muscular
weakness. Eosinophilic myofasciitis is associated with myalgias, skin induration, fatigue,and eosinophilia in the peripheral blood as well as in endomysial tissue.
Hyperthyroidism would cause a reduced TSH. It may cause weakness, but is generally associated
with other findings such as tremor, skin changes, and irritability.