Acne vulgaris

Simplified classification​​​[3]White GM. Recent findings in the epidemiologic evidence, classification, and subtypes of acne vulgaris. J Am Acad Dermatol. 1998 Aug;39(2 Pt 3):S34-7. http://www.ncbi.nlm.nih.gov/pubmed/9703121?tool=bestpractice.com

• Mild: comedones are the main lesions. Papules and pustules may be present but are small and few in number (generally <10).

• Moderate: moderate numbers (10-40) of papules and pustules. Moderate numbers (10-40) of comedones are also present. Sometimes mild truncal disease.

• Moderately severe: numerous papules and pustules (40-100), usually with many comedones (40-100) and the occasional (up to 5) larger, deeper nodular inflamed lesions. Widespread affected areas usually involving face, chest, and back.

• Very severe: nodulocystic acne and acne conglobata with severe lesions; many large, painful nodular/pustular lesions along with many smaller papules, pustules, and comedones.

Investigator’s Global Assessment (IGA) severity scale​[4]US Food and Drug Administration. Acne vulgaris: establishing effectiveness of drugs intended for treatment. May 2018 [internet publication]. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/acne-vulgaris-establishing-effectiveness-drugs-intended-treatment

Used primarily for research purposes, an example of which could be:

• Grade 0: clear skin with no inflammatory or non-inflammatory lesions

• Grade 1: almost clear; rare non-inflammatory lesions with no more than 1 small inflammatory lesion

• Grade 2: mild severity; greater than grade 1; some non-inflammatory lesions with no more than a few inflammatory lesions (papules/pustules only, no nodular lesions)

• Grade 3: moderate severity; greater than grade 2; up to many non-inflammatory lesions and may have some inflammatory lesions, but no more than 1 small nodular lesion

• Grade 4: severe; greater than grade 3; up to many non-inflammatory and inflammatory lesions, but no more than a few nodular lesions.