Rheumatology Made Simple : Proximal Myopathy

 PROXIMAL MYOPATHY

Muscle weakness can also be classified as either "proximal" or "distal" based on the location of the muscles that it affects. Proximal muscle weakness affects muscles closest to the body's midline, while distal muscle weakness affects muscles further out on the limbs.

Proximal myopathy presents as symmetrical weakness of proximal upper and/or lower limbs.

Patient usually finds it difficult to climb stairs.

They may also present with  falls.

Also patient will be unable to get up / stand up from sitting position without support or aid.

CAUSUES

There is a broad range of underlying causes including

Drugs

Excessive steroids in Rheumatoid Arthritis , SLE or Asthma)  

Statins

Alcohol

Endocrinological diseases

Thyroid disease and

Cushings Syndrome,

Addisons Disease ,

Acromegaly,

Diabetes

Osteomalacia

Idiopathic inflammatory myopathies (IIM)

Hereditary myopathies

Malignancy /Cancer  and paraneoplastc syndromes

Inflammatory:

Polymyositis &dermatomyositis.

Mixed connective tissue disease

Other connective tissue disease eg.

SLE

Vasculitis

Rheumatoid Arthritis

Systemic sclerosis.

Infections

Bacterial infections,

HIV

Cytomegalovirus  

Ebstein Barr Virus  

Hepatitis

Metabolic disorders and pathologies

Renal failure

Hepatic failure

Electrolyte disturbance

Miscellaneous causes

Inclusion body myositis,

Rhabdomyolysis,

Sarcoidosis

Mitochondrial myopathies

Muscular dystrophies

CLINICAL EXAMINATION

Inspection

Look for any wasting of muscles and any fasciculations

Is the wasting symmetrical or asymmetrical

Look for any walking aid

Palpation

Palpate muscles for bulk and tenderness

Ask patient to rise from sitting with arms crossed.

Ask them to raise arms above head and note if the weakness proximal or distal or both?

Examine tone of muscles

Usually normal in Proximal myopathy

Examine and Grade power in upper and lower limbs according to MRC Scale.

Power (MRC grade) and.

Reflexes (normal)

Sensation (normal unless peripheral neuropathy too)

Coordination (normal  or in proportion to weakness)

Does the patient appear Cushingoid from steroid use?

Any signs of Myasthenia gravis eg ptosis and fatiguability on repetition of movements.

Any fasciculations eg in Motor Neuron Disease.

Investigations

Bloods

Routine (FBC, U+E, LFT, Ca, P, Mg)

CK, AST, ALT, LDH

HBa1C, fasting glucose, cortisol, HIV, Hepatitis screen, CMV/EBV/adenovirus, serum ACE

Rheumatological screen:

ESR 

CRP 

ANA

ANCA

Rheumatoid factor

Anti-CCP

MRI muscle eg. thigh (inflamed muscle)

Cancer screen if dermato/polymyositis: FOB, CXR, mammogram, CT, tumour markers (PSA, CEA, CA125, CA19-9, CA15-3)

Keep common causes in mind eg

Vitamin D levels and bone profile

Thyroid function Tests

Creatine Kinase

Routine blood tests eg Full blood count

Renal function tests

Random blood sugar and HbA1c

To exclude other causes , we may need to opt for Neurophysiological studies and muscle investigations eg Muscle imaging and muscle biopsy after decision and evaluation by a specialist doctor.

MANAGEMENT

Management depends on underlying cause, and includes measures such as

Removal of offending agent

Correction of endocrine or metabolic problem,

Immunosuppressive therapy for Inflammatory muscle disorders

Physical therapy

Rehabilitation

Genetic counselling for muscular dystrophies.