Bohan & Peter Criteria (Polymyositis/Dermatomyositis)
Bohan & Peter criteria (1975): symmetric proximal weakness, elevated muscle enzymes, myopathic EMG, abnormal biopsy, and a dermatomyositis rash classify polymyositis (no rash) or dermatomyositis (rash) by the count of core criteria.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Symmetric proximal muscle weakness
- Yes
- Elevated serum muscle enzymes
- Yes
- Myopathic EMG changes
- Yes
- Abnormal muscle biopsy
- No
- Dermatomyositis rash
- Yes
Result: Bohan & Peter: definite dermatomyositis (3 of 4 core criteria + rash).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Polymyositis
- No rash: definite = 4 of the first 4 criteria, probable = 3, possible = 2.
- Dermatomyositis
- Rash present: definite = rash + 3, probable = rash + 2, possible = rash + 1. A classification, not a treatment order.
What you enter
- Symmetric proximal muscle weakness
- Elevated serum muscle enzymes
- Myopathic EMG changes
- Abnormal muscle biopsy
- Dermatomyositis rash (heliotrope / Gottron)
How this is calculated
Bohan A, Peter JB. Polymyositis and dermatomyositis (first of two parts). N Engl J Med. 1975;292(7):344-347. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.