Diagnostic Criteria for IBM.

Site presented by Bill Tillier

Several different sets of criteria:



The International Myositis Assessment and Clinical Studies Group (IMACS) is a coalition of health care providers and researchers with experience and interest in the myositis syndromes.

The administrative arm of IMACS is housed in offices of the National Institute of Environmental Health Sciences (NIEHS) in the Mark O. Hatfield Clinical Research Center at the National Institutes of Health, Bethesda, MD, USA.

A number of classification criteria for idiopathic inflammatory myopathies and the major subgroups have been proposed over the last three decades. Unfortunately, most of these have been based on clinical impressions rather than data analyses, and none have been fully tested for sensitivity or specificity using appropriately powered studies against all the appropriate disease confounders.
Realizing that such differences in criteria by various specialties threaten to create growing difficulties in comparing studies and clinical trials in the future, a number of experts in the field have joined together to initiate a new large, multicentered and multispecialty investigation to meet this need. This effort is called the International Myositis Classification Criteria Project and more information about it is available at

International Myositis Classification Criteria Project Workshop
Washington, DC November 10-11, 2005 IMCCP Steering Committee

Chronology of Published Diagnostic/Classification Criteria for IIM
-Medsger et al. 1970, Am. J. Med 48:715 (IIM)
-DeVere andamp; Bradley 1975, Brain 98:637 (IIM)
-Bohan andamp; Peter 1975, NEJM 292:344 and 403 (PM/DM)
-Dalakas 1991, NEJM 325:1487 (PM/DM/IBM)
-Griggs et al. 1995, Ann Neurol 38:705 (IBM)
-Tanimoto et al. 1995, J Rheum 22:668 (PM/DM)
-Targoff et al. 1997, Curr Opin Rheum 9:527 (IIM)
-Mastaglia andamp; Phillips 2002, Rheum Dis Clin N Am 28:723 (PM/DM/IBM)
-Van der Meulen et al. 2003, Neurol 61:316 (PM/DM/other)
-Dalakas andamp; Hohlfeld 2003, Lancet 362:971 (PM/DM)
-Hoogendijk, Amato et al. 2003, Neuro Dis 14:337 (ENMC for PM/DM)

-Griggs et al. 1995, Ann Neurol 38:705 (IBM)
A. Clinical Features
-1. Duration andgt; 6 mos
-2. Age of onset andgt; 30 yrs
-3. Pattern of Weakness
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;a. Finger flexor weakness
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;b. Wrist flexor andgt; wrist extensor weakness
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;c. Quadriceps weakness (= or andlt; MRC grade 4)

B. Laboratory Features
-1. Serum CK andlt; 12 x normal
-2. Muscle biopsy
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;a. mononuclear inflammatory cells invasion of non-necrotic muscle fibers
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;b. vacuolated muscle fibers
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;c. either
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;i. Intracellular amyloid deposits
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;ii. 15-18 nm tubulofilaments by EM
-3. EMG
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;a.'Features of an inflammatory myopathy'
andnbsp;andnbsp;andnbsp;andnbsp;andnbsp;b. May have long-duration MUAPs
Definite IBM
andnbsp;andnbsp;andnbsp;Patient must exhibit all muscle biopsy features
andnbsp;andnbsp;andnbsp;None of the clinical or other laboratory features are required if patient meets Bx criteria
Possible IBM
andnbsp;andnbsp;andnbsp;Bx shows only inflammation and invasion of fibers without vacuoles, amyloid, or TF on EM
andnbsp;andnbsp;andnbsp;Meets all Clinical Criteria (1,2,3) and other lab criteria (1,3)

Reference: Robert C. Griggs, Valerie Askanas, Salvatore DiMauro, Andrew Engel, George Katpati, Jerry R. Mendell, and Lewis P. Rowland, Inclusion Body Myositis and Myopathes Annals of Neurology Vol 38 No 5 November I995 705-713.


Classification and Diagnostic Criteria for Inclusion Body Myositis

I. Characteristic Features - Inclusion Criteria

A. Clinical features

Duration of illness greater than 6 months
Age of onset greater than 30 years old
Muscle weakness
Must affect proximal and distal muscles of arms and legs and
Patient must exhibit at least one of the following features:
Finger flexor weakness
Wrist flexor greater than wrist extensor weakness
Quadriceps muscle weakness (equal to or less than grade 4 MRC)

B. Laboratory features
Serum creatine kinase less than 12 times normal
Muscle biopsy
Inflammatory myopathy characterized by mononuclear cell invasion of nonnecrotic muscle fibers
Vacuolated muscle fibers
-Intracellular amyloid deposits (must use fluorescent method of identification before excluding the presence of amyloid) or
-15-18-nm tubulofilaments by electron microscopy
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
Patient 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 15-18-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 biopsy shows only inflammation (invasion of nonnecrotic muscle fibers by mononuclear cells) without other pathological 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.

Above from: myositis.org/template/page.cfm?id=69 (defunct)




-Male preponderance: 60% to 75%
-Onset > 50 years in 80%

Sporadic Form

-Clinical features
---Proximal and Distal: Distal predominant in 20%
---Upper and Lower extremities
---Focal regions with more severe weakness: Wrist and finger flexors; Quadriceps
---Muscles commonly spared: Deltoid; Pectoralis; Interossei (Hands); Face
----Slow over 5 to 20 years
----? More rapid progression to disability with onset after 60 years
--Muscle atrophy: Proportionate to weakness
--Tendon reflexes: Diminished with disease progression, especially knee
--Dysphagia (30%): Upper 1/3 of esophagus; Especially females
---Usually subclinical
---Sensory > Motor
---Loss of myelinated axons in sural nerve
--Systemic involvement
---No strong systemic disease associations
---Reports of associated: Immune disorders, Polyneuropathy
---No association with malignancy


-Serum CK: Mildly elevated 2 to 5 fold; May be normal

-EMG: Irritable myopathy; Long duration potentials may occur

-Muscle Pathology

--Endomysial inflammation
--Myopathic changes + groups of small fibers
--Rimmed vacuoles with granular material and filaments
---Histochemistry: Best visualized with Congo Red stain
-----Filaments: 15 to 18 nm
-----Several proteins b-Amyloid, Desmin; Ubiquitin; Transglutaminases 1 and 2
--Accumulations of aB-crystallin in muscle fibers: May occur before myopathic or vacuolar D
--Mitochondrial D: COX- muscle fibers and multiple mDNA deletions in 50%
--Muscle fiber hypertrophy: More common than in polymyositis

-Other Lab
--M-protein (20%): Most IgG; l > k
--HLA types: DRb1*0301, DRb3*0101 (or DRb3*0202) and DQb1*0201
--? Excess frequency of e4 allele of apolipoprotein E in males with IBM
--20x Elevated level of muscle transglutaminase activity


None; Few reports of response to IVIG or immunoabsorption


Autosomal dominant inheritance
-Similar clinical features to sporadic IBM
-No HLA type association

Above from: http://neuromuscular.wustl.edu/antibody/infmyop.htm#ibm


The European Neuromuscular Centre Criteria for IBM:

View here as a PDF file.

This is a chapter from a book: Emery, A. (Ed.) (1997) Diagnostic Criteria for Neuromuscular Disorders. 2nd edition. ISBN: 1-85315-301-X. A. E. H. Emery is the Research Director, European Neuromuscular Centre, Baarn, The Netherlands.

Mail Bill: btillier@shaw.ca

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