Gout
Gout is a complex metabolic inflammatory arthritis. It is driven by chronically high blood uric acid (hyperuricemia), which leads to deposits of monosodium urate (MSU) crystals in joints, tendon sheaths and soft tissues, and notably in the dermis and subcutis, where they form cutaneous tophi.
In metabolic dermatology at Haute-Derma, we see gout as more than a joint disease. It can cause serious skin complications, including ulcerated and draining tophi, soft tissue necrosis, secondary infection and disfiguring changes to the skin. Recognizing tophi under the skin early helps prevent widespread tissue damage and preserves the patient's mobility.
Pathogenesis and Characteristic Clinical Forms
Tophi and the skin complications of gout develop through chronic inflammation and gradual microscopic crystal deposition:
- Crystal precipitation and the inflammatory response (inflammasome activation):
- When blood uric acid rises above its physiological solubility limit (> 6.8 mg/dL, or 400 µmol/L), MSU crystals begin to precipitate in cooler tissues such as the toes, ears and hands.
- MSU crystals activate macrophages through the NLRP3 inflammasome, triggering a surge of potent pro-inflammatory cytokines (IL-1β, TNF-α, IL-6). These recruit neutrophils and set off acute arthritis and acute skin inflammation.
- Tophaceous granuloma formation: In the chronic stage, layer upon layer of deposited MSU crystals becomes surrounded by multinucleated giant cells, macrophages and epithelioid cells, forming stone-hard fibrotic granulomas in the deep dermis and subcutaneous tissue.
Clinical Forms Seen in the Skin
- Acute gout attack in the skin and joint (acute gouty arthritis): Comes on suddenly, often at night. The skin over the joint (most often the big toe joint, known as podagra) becomes swollen, hot, bright red and shiny, intensely painful and extremely sensitive to touch.
- Chronic subcutaneous tophi (chronic tophaceous gout): Firm nodules or lumps, painless at first, ivory-white or pale yellow, visible under the skin. Favored sites are the ears, the tip of the elbow, the Achilles tendon, the top of the foot and the finger joints.
- Ulcerated or draining tophi: A large tophus thins the overlying epidermis until it breaks open and drains thick, chalky or toothpaste-like material containing MSU crystals. These ulcers are easily infected by bacteria (staphylococci, streptococci), leading to skin necrosis.
- Rare extra-articular skin form (intradermal gout): Urate crystals deposit directly in the superficial dermis as opaque yellow papules and plaques that can be mistaken for xanthoma or calcinosis cutis.
Stages and Clinical Features
| Stage | Uric Acid Level and Skin Findings | Histologic Features |
|---|---|---|
| Asymptomatic hyperuricemia | Uric acid > 6.8 mg/dL; no clinical symptoms or tophi yet | No significant microscopic deposits yet |
| Acute gout | Hot, red, swollen and intensely painful joint and overlying skin | Dense neutrophil infiltrate around MSU crystals |
| Chronic tophaceous gout | Firm white/yellow nodules clearly visible under the skin of the ears, fingers and elbows | Fibrous granuloma surrounding a core of needle-shaped urate crystals |
| Ulcerated / draining tophi | Skin breaks down and drains chalky white material; risk of necrosis and infection | Dermal necrosis, loss of basement membrane structure, bacterial invasion |
Our Diagnostic Workup at Haute-Derma
- Clinical examination and dermoscopy: Identifies typical tophi. Dermoscopy shows an opaque ivory-white or yellowish center surrounded by a network of dilated vessels at the edge of the nodule.
- High-frequency skin ultrasound (HFUS, 22–50 MHz):
- Looks for the characteristic double contour sign on the surface of the joint cartilage.
- Measures the volume of the tophus and assesses how far it extends into tendon sheaths and subcutaneous fat, and its relationship to major blood vessels.
- Polarized light microscopy: Fluid aspirated from the joint or drained from a tophus is examined for needle-shaped monosodium urate crystals showing strong negative birefringence.
- Blood tests and systemic assessment: Serum uric acid, CRP, erythrocyte sedimentation rate (ESR) and kidney function (urea, creatinine), plus urinary tract ultrasound to rule out urate stones.
Microsurgical and Laser Treatment at Haute-Derma
At Haute-Derma, we pair systemic urate-lowering treatment with local surgical and laser procedures to clear skin lesions and tophi:
Systemic Medical Treatment
- Controlling acute flares: Low-dose colchicine combined with nonsteroidal anti-inflammatory drugs (NSAIDs) or a short course of corticosteroids.
- Urate-lowering therapy (ULT): Xanthine oxidase inhibitors (febuxostat or allopurinol) keep serum uric acid below a target of 5 mg/dL (300 µmol/L) in patients who already have tophi, so that deposited crystals gradually dissolve.
Tissue-Sparing Microsurgical Removal of Tophi
- Indications: Large tophi pressing on tendons or vessels, tophi that have broken open and are draining, or tophi that are seriously disfiguring on the hands, feet or face.
- Technique:
- A small micro-incision placed along natural skin creases.
- Gentle dissection frees the chalky tophaceous core from its fibrous capsule without injuring nearby tendons and vessels.
- Residual MSU microcrystals are flushed out with warm saline.
- Benefits: Removes the source of chronic inflammation right away, prevents skin necrosis, speeds wound healing and gives the best cosmetic result.
UltraPulse CO2 Laser for Clearing Superficial Tophi and Ulcers
- Indications: Superficial tophi in the epidermis or dermis (ears, fingers), or small draining tophaceous sinuses that are hard to remove with conventional surgery.
- Technique: The 10,600 nm CO2 laser precisely ablates necrotic skin, vaporizes superficial urate deposits and sterilizes the surface of the sinus, promoting rapid wound healing and granulation tissue formation.
