Cutaneous Sarcoidosis
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Direct answer
Cutaneous sarcoidosis is a granulomatous skin disease of unknown cause, occurring with or without systemic involvement, most often in the lungs and lymph nodes. It produces papules, plaques and lupus pernio, with non-caseating epithelioid granulomas that are often naked, lacking a surrounding lymphocyte cuff. Tuberculosis and leprosy must be excluded first, because both also produce granulomas.
What you must remember
- Lupus pernio: violaceous plaques on the nose, cheeks, ears and fingers, linked with chronic pulmonary and upper airway disease and carrying a poorer prognosis.
- Scar sarcoid: granulomatous infiltration of old scars, including tattoos, which is a clinical clue to systemic disease.
- Naked granulomas: non-caseating epithelioid granulomas without a lymphocytic rim, the histological clue most often sought in exams.
- Lofgren syndrome: erythema nodosum, bilateral hilar lymphadenopathy and ankle arthralgia, generally with a favourable course.
- Chest radiograph: bilateral hilar lymphadenopathy is the commonest initial finding in systemic disease, so a chest film is essential.
- Infection exclusion: acid-fast staining and culture of tissue, a Mantoux or interferon-gamma release assay, and a leprosy assessment all mimic sarcoid granulomas.
- Supportive tests: serum calcium and angiotensin-converting enzyme help judge extent but do not confirm the diagnosis.
- Treatment: potent topical or intralesional corticosteroids for limited skin disease, with methotrexate or hydroxychloroquine for widespread disease and systemic steroids for organ involvement.
A stepwise approach to a granulomatous skin lesion
A 34-year-old woman has had violaceous plaques across her nose and cheeks for two years, with a dry cough that has come and gone. A biopsy from one plaque shows non-caseating granulomas, and she asks whether this is simply a skin problem.
- Confirm the granulomas: non-caseating epithelioid granulomas on biopsy define the lesion, and special stains are then used to look for organisms.
- Exclude infection first: acid-fast staining and culture on tissue, a Mantoux or interferon-gamma assay and a leprosy examination come before any sarcoid label, since mycobacterial disease can produce similar granulomas.
- Image the chest: a chest radiograph showing bilateral hilar lymphadenopathy or pulmonary shadowing points to systemic disease and guides the next tests.
- Check the blood: serum calcium, angiotensin-converting enzyme, and liver and renal function help assess the extent of disease and the safety of treatment.
- Examine the eyes: uveitis is the commonest ocular involvement and needs slit-lamp review, because it threatens vision.
- Choose therapy by extent: intralesional steroids suit limited plaques, while methotrexate or hydroxychloroquine is chosen for widespread skin disease and systemic steroids for organ disease.
Where the exam tries to catch you
Three traps recur when a granuloma is found on biopsy.
- Trap: diagnosing sarcoidosis from granulomas without excluding tuberculosis or leprosy. Correct: granulomas are not specific, so staining, culture and leprosy assessment come first.
- Trap: reading a negative Mantoux test as evidence against tuberculosis. Correct: sarcoidosis can suppress the tuberculin reaction, so a negative test does not rule out infection.
- Trap: treating lupus pernio as a simple cosmetic plaque. Correct: lupus pernio is linked with chronic pulmonary disease, so chest and airway review are part of its management.
Frequently asked questions
What is the characteristic histology of cutaneous sarcoidosis?
Cutaneous sarcoidosis shows non-caseating epithelioid granulomas, often naked, meaning they lack a surrounding lymphocytic rim. The absence of caseation helps separate sarcoid granulomas from tuberculosis.
Which investigation is the first step in the systemic work-up of cutaneous sarcoidosis?
A chest radiograph is the usual first investigation, and bilateral hilar lymphadenopathy is its classic finding in sarcoidosis. Serum calcium and angiotensin-converting enzyme add support, but they do not confirm the diagnosis of cutaneous sarcoidosis.
Why does lupus pernio carry a worse prognosis in cutaneous sarcoidosis?
Lupus pernio is associated with chronic pulmonary and upper airway involvement and tends to persist for years. It also disfigures the nose, which is why it is treated more actively than a simple sarcoid plaque.
What is Lofgren syndrome and how does it differ from chronic cutaneous sarcoidosis?
Lofgren syndrome is an acute form of sarcoidosis with erythema nodosum, bilateral hilar lymphadenopathy and ankle arthralgia. It usually has a favourable course, unlike chronic lupus pernio, and often resolves without long-term treatment.