Chloracne

Chloracne is a severe acneiform eruption caused by systemic absorption of halogenated aromatic hydrocarbons. It marks significant systemic exposure and is a sensitive skin sign of toxicity.

Causative agents. Chlorinated dioxins (especially 2,3,7,8-tetrachlorodibenzo-p-dioxin), polychlorinated dibenzofurans, polychlorinated biphenyls, chlorinated naphthalenes, hexachlorobenzene and some chlorinated herbicides and wood preservatives.

Exposure. Chlorophenol and herbicide manufacture, transformer and capacitor work, waste incineration, chemical plant accidents and contaminated cooking oil. Absorption occurs through skin, lungs and gut.

Epidemiology. Rare in current practice and usually linked to accidents or poorly controlled processes. Onset is weeks to a few months after a high exposure.

Course. Lesions can persist for years or decades because the compounds are fat soluble and eliminated slowly. The half life of the main dioxin is about 7 to 9 years.

Pathophysiology.

Halogenated aromatics bind the aryl hydrocarbon receptor, altering keratinocyte differentiation and converting sebaceous glands to keratinising cysts. Follicular plugging with large cysts results.

The same receptor mechanism underlies hepatic enzyme induction, porphyrin disturbance, lipid abnormalities and probable carcinogenicity.

• Open comedones and yellow cysts, most marked on the malar region, temples, behind the ears, axillae, groin and genitals.
• Hyperpigmentation, hirsutism, nail pigmentation, and cystic change of the eyelid glands with conjunctival discharge.
• Systemic features: fatigue, weight loss, liver enzyme elevation, hyperlipidaemia, porphyria cutanea tarda, peripheral neuropathy and thyroid or glucose abnormalities.

Red flags.

• Jaundice, dark urine with blistering photosensitive skin (porphyria cutanea tarda).
• Progressive weakness or sensory loss.
• Weight loss, lumps or other features of malignancy.

• Exposure history including process, accidents and co-worker cases.
• Examination of characteristic sites, eyelids and nails.
• Liver enzymes, GGT, fasting lipids, glucose, thyroid function, full blood count and urinary porphyrins.
• Serum or adipose assay of dioxin and biphenyl congeners in a specialist laboratory, adjusted for lipid content.
• Skin biopsy when unclear: loss of sebaceous glands, infundibular keratinous cysts.
• Nerve conduction studies for neuropathy.

Differential diagnosis. Acne vulgaris, oil acne, steroid and drug induced acneiform eruption, epidermoid cysts, hidradenitis suppurativa, rosacea, hyperandrogenism.

• Remove from exposure and decontaminate skin and clothing; control the process source.
• Topical retinoid: adapalene 0.1% gel topically once daily at night, long term. Maximum one thin application daily. Monitor irritation and photosensitivity. Avoid in pregnancy; no renal or hepatic adjustment.
• Doxycycline 100 mg orally once daily with food and a full glass of water for up to 12 weeks. Maximum 100 mg daily. Monitor photosensitivity and oesophagitis. Avoid in pregnancy, breastfeeding and under 12 years; no renal adjustment; caution in hepatic impairment.
• Isotretinoin gives variable benefit and adds hepatic and lipid burden. When used: 0.5 mg/kg daily with food, increasing to 1 mg/kg daily if tolerated, to a cumulative dose of 120 to 150 mg/kg. Maximum 1 mg/kg daily. Monitor liver enzymes and fasting lipids at baseline, 1 month and every 3 months, monthly pregnancy tests and mood. Contraindicated in pregnancy, breastfeeding, hepatic impairment, uncontrolled hyperlipidaemia and with tetracyclines; start at 10 mg daily in severe renal impairment. Specialist use only.
• Surgical options: cyst incision and expression, excision of persistent cysts, and laser or dermabrasion for scars.
• Avoid sun exposure and use sunscreen when porphyria is present. Treat hyperlipidaemia and porphyria cutanea tarda by specialist care.

Monitoring. Liver enzymes, lipids, glucose, thyroid function and urinary porphyrins at baseline and every 6 to 12 months; skin and neurological review at each visit.

Referral and escalation. Dermatology and occupational physician at diagnosis; hepatology for abnormal liver tests; toxicology for high measured body burden; notification and compensation where required.

Special groups. Pregnancy: avoid retinoids and tetracyclines; the compounds cross the placenta and enter breast milk, so exposure review is needed.