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Home Criteria Neurology Diagnostic Criteria for Inclusion Body Myositis (IBM)


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Diagnostic Criteria for Inclusion Body Myositis (IBM) Print E-mail
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Written by G. Firman MD   
Monday, 11 July 2016 07:21


Inclusion body myositis is the most common myopathy in patients over the age of 40 years encountered in neurological practice. Although it is usually sporadic, there is increasing awareness of the influence of genetic factors on disease susceptibility and clinical phenotype. The diagnosis is based on recognition of the distinctive pattern of muscle involvement and temporal profile of the disease, and the combination of inflammatory and myodegenerative changes and protein deposits in the muscle biopsy.


Griggs Diagnostic Criteria for Inclusion Body Myositis

I. Characteristic features of inclusion body myositis

A. Clinical features

  1.  Duration of illness > 6 months
  2.  Age of onset > 30 years old
  3.  Muscle weakness

 Must affect proximal and distal muscles of arms and legs and patient must exhibit at least one of the following features:

a. Finger flexor weakness

b. Wrist flexor> wrist extensor weakness

c. Quadriceps muscle weakness (= or < grade 4 MRC)

 B. Laboratory features

  1.  Serum creatine kinase < 12 times normal
  2.  Muscle biopsy

a. Inflammatory myopathy characterized by mononuclear cell invasion of nonnecrotic muscle fibers

b. Vacuolated muscle fibers

c. Either

 (i) Intracellular amyloid deposits (must use fluorescent method of identification before excluding the presence of amyloid) or

 (ii) 15–18-nm tubulofilaments by electron microscopy

3. Electromyography must be consistent with features of an inflammatory myopathy (however, long-duration potentials are commonly observed and do not exclude diagnosis of sporadic inclusion body myositis).

 C. Family history

Rarely, inclusion body myositis may be observed in families. This condition is different from hereditary inclusion body myopathy without inflammation. The diagnosis of familial inclusion body myositis requires specific documentation of the inflammatory component by muscle biopsy in addition to vacuolated muscle fibers, intracellular (within muscle fibers) amyloid, and 15–18-nm tubulofilaments.

II. Associated disorders

Inclusion body myositis occurs with a variety of other, especially immune-mediated conditions. An associated condition does not preclude a diagnosis of inclusion body myositis if diagnostic criteria (below) are fulfilled.

III. Diagnostic criteria for inclusion body myositis

A. Definite inclusion body myositis

Patients must exhibit all muscle biopsy features including invasion of nonnecrotic fibers by mononuclear cells, vacuolated muscle fibers, and intracellular (within muscle fibers) amyloid deposits or 15- to 18-nm tubulofilaments.

None of the other clinical or laboratory features are mandatory if muscle biopsy features are diagnostic.

B. Possible inclusion body myositis

If the muscle shows only inflammation (invasion of nonnecrotic muscle fibers by mononuclear cells)—without other pathologic features of inclusion body myositis—then a diagnosis of possible inclusion body myositis can be given if the patient exhibits the characteristic clinical (A1,2,3) and laboratory (B1,3) features.



Modified Inclusion Body Myositis Diagnostic Criteria 2008

Pathologically defined inclusion body myositis

• Conforming to the Griggs criteria: Invasion of nonnecrotic fibers by mononuclear cells and rimmed vacuoles, and either intracellular amyloid deposits or 15- to 18-nm filaments.

Clinically defined inclusion body myositis

 • Clinical features

* Duration of weakness > 12 months

* Age > 35 years

* Weakness of finger flexion > shoulder abduction AND of knee extension > hip flexion

 • Pathologic features

* Invasion of nonnecrotic fibers by mononuclear cells or rimmed vacuoles or increased

* Major Histocompatibility Complex class 1 (MHC-1), but no intracellular amyloid deposits or 15- to 18-nm filaments

Possible IBM

 • Clinical criteria

* Duration of weakness >12 months

* Age > 35 years

* Weakness of finger flexion > shoulder abduction OR of knee extension > hip flexion

 • Pathologic criteria

* Invasion of nonnecrotic fibers by mononuclear cells or rimmed vacuoles or increased

* MHC-1, but no intracellular amyloid deposits or 15- to 18-nm filaments





References:

  1. Dimachkie MM, Barohn RJ. Inclusion body myositis. Semin Neurol. 2012 Jul;32(3):237-45. [Medline]
  2. Griggs RC, Askanas V, DiMauro S, Engel A, Karpati G, Mendell JR, Rowland LP. Inclusion body myositis and myopathies. Ann Neurol. 1995 Nov;38(5):705-13. [Medline]
  3. Hilton-Jones D, Brady S. Diagnostic criteria for inclusion body myositis. J Intern Med. 2016 Jul;280(1):52-62. [Medline]



Created: Jul 11, 2016.


Last Updated on Thursday, 28 July 2016 05:06
 

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