DermatologyTier 1Disease (DEADMAN)

Cutaneous manifestations of systemic diseases - acne

Description

Acne as a sign pointing to an underlying systemic driver, rather than primary acne vulgaris of adolescence (see standalone acne note for routine disease/topical-to-isotretinoin management)
Red flags for a systemic cause: sudden severe onset, onset outside the typical teenage window, resistance to standard therapy, or accompanying virilisation/systemic symptoms
Two broad categories: androgen-excess acne and drug-induced acne

Adult-onset/persistent female acne - common presentation of PCOS (affects up to ~10% of women of reproductive age)
Acne fulminans - rare, adolescent males predominantly
Drug-induced (steroid) acne - common wherever systemic/high-dose topical corticosteroids or anabolic steroids are used

Androgen-excess acne

Androgens -> inc sebaceous gland size and sebum production -> follicular hyperkeratinisation -> comedone formation -> Cutibacterium acnes proliferation -> inflammation
PCOS - commonest cause, insulin resistance -> inc ovarian androgen production
Congenital adrenal hyperplasia (late-onset/non-classic) - adrenal androgen excess
Androgen-secreting tumour (ovarian/adrenal) - rare but important not to miss - suspect with rapid onset + virilisation (hirsutism, clitoromegaly, voice change, male-pattern balding)
Cushing's syndrome - glucocorticoid + androgen excess

Drug-induced

Systemic/topical corticosteroids - monomorphic papulopustular eruption, sudden onset with steroid initiation, distinct from comedonal acne vulgaris
Anabolic-androgenic steroids - truncal, severe, in gym/bodybuilding context
Lithium, isoniazid, phenytoin, EGFR inhibitors (papulopustular, not true acne but clinically mimics), testosterone therapy

Acne fulminans (severe variant with systemic features)

Abrupt, severe, ulcerative/haemorrhagic acne with fever, arthralgia, systemic inflammatory markers raised - an inflammatory syndrome, not simple infection
SAPHO syndrome - Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis - acne as part of a seronegative spondyloarthropathy spectrum

When to investigate for a systemic cause

Adult-onset or treatment-resistant acne in a woman with irregular menses, hirsutism, or other signs of hyperandrogenism - screen for PCOS (testosterone, LH/FSH ratio, pelvic ultrasound) and rule out late-onset CAH (17-OH progesterone)
Rapid-onset virilisation - urgent imaging (pelvic/adrenal) to exclude androgen-secreting tumour
Acne temporally linked to a new medication - drug-induced acne is a clinical/exclusion diagnosis
Acne fulminans - inflammatory markers (ESR/CRP), consider bone imaging if SAPHO features (joint/bone pain)

A. Treat the underlying driver, alongside standard acne therapy

PCOS-related - combined oral contraceptive pill (anti-androgenic progestin e.g. cyproterone/drospirenone where suitable) +/- spironolactone (anti-androgen) alongside topical/oral acne therapy; metformin/weight management for the metabolic phenotype
CAH - low-dose glucocorticoid replacement, endocrinology-led
Androgen-secreting tumour - surgical resection
Drug-induced - cease/substitute the causative agent where feasible; standard topical acne therapy for symptom control while awaiting resolution

B. Acne fulminans/SAPHO

Systemic corticosteroids first (dampen the inflammatory flare) before starting isotretinoin - starting isotretinoin alone in the acute flare can worsen it
Once stabilised, transition to isotretinoin under steroid cover
SAPHO - rheumatology involvement, NSAIDs, bisphosphonates for osteitis, biologic therapy (anti-TNF) for refractory disease

PCOS - hirsutism, oligomenorrhoea/anovulation, insulin resistance, metabolic syndrome
Late-onset CAH - hirsutism, subfertility
Cushing's syndrome - central obesity, striae, proximal myopathy
SAPHO - inflammatory bone/joint disease, palmoplantar pustulosis
Anabolic steroid use - other virilising/psychiatric effects

Treating the systemic driver (e.g. PCOS therapy) typically improves acne alongside the primary condition, but standard topical/oral acne therapy is usually still needed concurrently
Missed androgen-secreting tumour - progressive virilisation, delayed diagnosis carries oncological consequences
Acne fulminans - risk of significant scarring if the inflammatory flare is not controlled promptly with steroids before/alongside isotretinoin
Drug-induced acne - typically resolves on cessation of the causative agent, though may take weeks-months

6 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.