What is Sarcoidosis of Skin
Cutaneous sarcoidosis is a manifestation of sarcoidosis—a multisystem granulomatous disease of unknown cause—that affects the skin in 20-30% of patients, presenting most commonly as pink-red to red-brown papules and plaques on the head and neck, characterized histologically by non-caseating granulomas 1, 2.
Disease Definition and Pathophysiology
Sarcoidosis is a systemic inflammatory disorder where organized collections of epithelioid histiocytes form non-necrotic granulomas, predominantly composed of T cells with interposed dendritic cells 3. The skin involvement represents a macrophage/T helper-1 cell-mediated granulomatous inflammation process driven by an imbalance between pro-inflammatory and anti-inflammatory cytokines 4.
Clinical Presentations
Cutaneous sarcoidosis is known as one of the "great imitators" in dermatology due to its polymorphous presentations 4, 5:
Specific Lesions (Contain Granulomas)
- Papules and plaques: Pink-red to red-brown, commonly affecting head and neck 1
- Lupus pernio: Violaceous, indurated plaques typically on nose, cheeks, and ears—considered highly probable for sarcoidosis diagnosis 3
- Scar sarcoidosis: Granulomas developing in old scars
- Maculopapular, erythematous, or violaceous lesions 3
- Subcutaneous nodules 3
- Rare forms: alopecia, ulcers, hypopigmented patches, ichthyosis 4, 5
Non-Specific Lesions
- Erythema nodosum: Acute presentation, often part of Löfgren's syndrome (bilateral hilar adenopathy + erythema nodosum + arthritis), which is highly probable for sarcoidosis 3, 6
Diagnostic Importance
The skin provides a readily accessible site for biopsy to establish definitive diagnosis 1. When sarcoidosis is suspected, dermatologic evaluation is particularly valuable because:
- Skin lesions offer visible clues to diagnosis 4, 5
- Biopsy is easily obtained for histologic confirmation
- Cutaneous involvement may herald systemic disease 6
Histopathologic Features
Non-caseating (non-necrotic) granulomas are characteristic, though variants can show mixed necrotic and non-necrotic patterns 3. Alternative causes must be excluded, including infections, malignancy, berylliosis, drug-induced granulomatous reactions (especially immune checkpoint inhibitors and anti-TNF agents), and hypersensitivity pneumonitis 3.
Clinical Evaluation Requirements
When cutaneous sarcoidosis is identified, three critical assessments are needed 6:
- Screen for visceral involvement: Particularly lungs (most common), eyes, lymphatic system, heart, liver, spleen, bones, kidneys
- Determine prognosis: Lupus pernio predicts poor cutaneous response 7
- Plan long-term monitoring and treatment
Organ Involvement Patterns
While skin is affected in 20-30% of cases, sarcoidosis most commonly involves 1, 2:
- Lungs (most frequent)
- Lymphatic system
- Eyes
- Skin
However, any organ system can be affected, making this a truly multisystem disease 4, 5.
Treatment Considerations
Treatment strategy depends on severity and distribution of skin lesions, incorporating patient preference and considerations for other involved organs 1. The disease can be frustrating to treat as lesions may be refractory or recur after successful treatment 4, 5. Prednisone and corticotropin repository are the only FDA-approved therapies for sarcoidosis 2.