Proximal myopathy

Published on 02/04/2015 by admin

Filed under Internal Medicine

Last modified 22/04/2025

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58 Proximal myopathy

Instruction

Perform a neurological examination of this patient’s arms or legs.

Salient features

History

• Weakness of proximal muscles

• Patient has difficulty in standing from the sitting position (getting up from chairs, getting off the commode) or difficulty in combing hair – elicit this history.

Examination

• Check the gait, looking for waddling gait (p. 251)

• Look for an underlying cause:

• Diabetic amyotrophy (asymmetrical, usually in the lower limbs in non-insulin-dependent diabetes mellitus)
• Cushing syndrome (characteristic facies, history of steroid ingestion; see p. 538)
• Thyrotoxicosis (look for eye signs, goitre, rapid pulse, tremor)
• Polymyositis (heliotropic rash, tender muscles)
• Drug history (alcohol, steroids, chloroquine)
• Carcinomatous neuropathy
• Osteomalacia (bone pain)
• Hereditary muscular dystrophy.

Diagnosis

This patient has weakness of the proximal muscles of the lower limbs (lesion) caused by Cushing syndrome (aetiology) and is severely limited by the weakness (functional status).

Questions

What is Gowers’ sign?

In severe proximal myopathy of the lower limbs, a patient on rising from the floor uses their hands against the body to climb up to vertical. It has been classically described in Duchenne muscular dystrophy.

What do you know about diabetic amyotrophy?

It is an asymmetrical motor polyneuropathy that presents with asymmetrical weakness and wasting of the proximal muscles of the lower limbs and sometimes upper limbs, diminished or absent knee jerk and sensory loss in the thigh. It is usually accompanied by severe pain in the thigh, often awakening the patient at night. The prognosis is good and most patients recover over months or years with diabetic control.

Advanced-level questions

What is the difference between type 1 and type 2 muscle fibres?

• Type 1 muscle fibres are high in myoglobin and oxidative enzymes and have many mitochondria. They perform tonic contraction and are involved in weight bearing and movements requiring sustained force. Chloroquine causes vacuolation of myocytes, predominantly type 1 fibres.

• Type 2 muscle fibres are rich in glycolytic enzymes; they perform rapid phasic contractions and are involved in sudden movements and in purposeful motion. In steroid myopathy the muscle fibre atrophy predominantly affects these fibres.

Sir WR Gowers (1845–1915), Professor of Medicine at University College Hospital, London, invented a haemoglobinometer, personally illustrated an atlas of ophthalmology and wrote a book on spinal cord diseases and a manual on the nervous system. He also founded a society of medical stenographers.

Guillaume-Bejmanin-Amand Duchenne (1806–75) was first to describe Duchenne muscular dystrophy in 1868 in a paper where he described 13 cases of the disease; by 1870 he had seen about 40 cases.

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