DR1.1-2 | Acne — Glossary

A chronic inflammatory disease of the pilosebaceous unit, commonest in adolescence, characterised by comedones, papules, pustules, nodules, and cysts in seborrhoeic areas.

A monomorphic papulopustular eruption resembling acne but lacking comedones, typically drug-induced and of abrupt onset.

A third-generation, photo-stable synthetic topical retinoid, generally better tolerated than tretinoin and widely used first-line for comedonal and mild-to-moderate acne.

Hormones (testosterone, and its potent derivative dihydrotestosterone formed by 5α-reductase) that stimulate sebaceous gland enlargement and sebum production, underlying the pubertal onset of acne.

The practice of limiting antibiotic courses to ~3 months, never using them as monotherapy, and always co-prescribing benzoyl peroxide, to minimise C. acnes resistance.

A topical agent with triple action in acne — anti-comedonal, antimicrobial against C. acnes, and anti-pigmentary (tyrosinase inhibition) — especially valuable where post-inflammatory hyperpigmentation accompanies acne and as a pregnancy-safe option.

Raised intracranial pressure risked by combining an oral tetracycline with isotretinoin — the reason these two drugs must never be co-prescribed.

A non-antibiotic bactericidal that kills C. acnes by oxidation without inducing resistance; the essential partner co-prescribed with any antibiotic to limit resistance.

A comedone with a narrow, covered follicular opening, so the plug is not oxidised; appears as a small skin-coloured or pale papule.

An oestrogen–progestin pill that reduces free androgens and raises sex-hormone-binding globulin, used in hormonal-pattern female acne; contraindicated in thromboembolic and other standard risk states.

The primary, defining lesion of acne — a plugged pilosebaceous follicle filled with keratin and sebum; open (blackhead) or closed (whitehead).

The total dose of isotretinoin received over a course (target approximately 120–150 mg/kg), associated with the lowest relapse rates; the exact figure should be confirmed against current guidance.

The anaerobic diphtheroid bacterium (formerly Propionibacterium acnes) that colonises the plugged, sebum-rich follicle and drives inflammation in acne.

Abnormal cohesion and retention of keratinocytes lining the follicular duct, plugging the follicle and forming the microcomedone — the first step in acne pathogenesis.

An objective, site-weighted acne severity score (region factor × lesion-density grade, summed) banding severity as mild (1–18), moderate (19–30), and severe (≥31).

Acne in adult women distributed over the lower face/jaw-line with premenstrual flares or signs of hyperandrogenism, indicating a role for hormonal therapy.

Excess androgen activity (e.g. in PCOS) producing severe, persistent, or sudden-onset acne, often with hirsutism and menstrual irregularity, warranting hormonal investigation.

A quick five-point (0–4) clinical scale of acne severity (clear, almost clear, mild, moderate, severe) widely used at the bedside and in trials.

A large (>5 mm), deep, firm, tender inflammatory acne lesion extending into the dermis; the lesion type most associated with scarring.

Severe acne characterised by deep inflammatory nodules and pus-filled pseudocysts, carrying a high risk of permanent scarring.

A comedone with a dilated, open follicular opening whose plug is exposed to air; the black colour is oxidised keratin and melanin, not dirt.

A tetracycline (commonly doxycycline) used for moderate inflammatory acne, limited to about three months, always with topical benzoyl peroxide and never as monotherapy or with isotretinoin.

13-cis-retinoic acid; the most effective acne drug, targeting all four pathogenetic pillars; reserved for severe/refractory acne; absolutely contraindicated in pregnancy and requiring mandatory pregnancy prevention and laboratory monitoring.

A small (<5 mm) solid, raised, red, tender inflammatory acne lesion without visible pus.

The functional skin unit comprising a hair follicle and its attached sebaceous gland; the structure in which all acne lesions arise.

Dark macules persisting at sites of resolved inflammatory acne lesions, especially prominent and distressing in skin of colour.

The structured protocol (negative pregnancy test before starting, effective contraception during and after, repeat testing) required for women of childbearing potential on isotretinoin; the iPLEDGE programme in the US, with local CDSCO equivalents in India.

An inflammatory acne lesion containing visible yellow-white pus at its apex.

A central-face chronic condition of adults with persistent erythema, flushing, telangiectasia, and papulopustules but NO comedones; the key acne mimic.

The lipid secretion of the sebaceous gland; produced in excess under androgenic stimulation in acne and serving as substrate for Cutibacterium acnes.

An aldosterone antagonist that blocks the androgen receptor and reduces sebum; used off-label for female acne, avoided in pregnancy, and not used in men for acne owing to feminising effects.

A severity-matched approach to acne treatment in which therapy starts at the rung corresponding to the patient's grade and steps up only if an adequate trial fails.

The capacity of a drug to cause birth defects; isotretinoin is a potent teratogen, making pregnancy an absolute contraindication and mandating rigorous pregnancy prevention.

Clindamycin or erythromycin applied to the skin to suppress C. acnes; must never be used as monotherapy — always combined with benzoyl peroxide or a retinoid to slow resistance.

A vitamin-A-derivative cream/gel (adapalene, tretinoin, tazarotene) that corrects follicular hyperkeratinisation — the backbone of acne therapy; irritant and (tretinoin) photolabile.

All-trans retinoic acid; a first-generation topical retinoid that is photodegradable and photosensitising, so it is applied at night with daytime sunscreen.