What is sarcoidosis?
Sarcoidosis is a granulomatous disease of unknown cause, characterised by non-caseating granulomas in organs and tissue, such as the skin, lung, lymph nodes, eyes, joints, liver, kidneys, and heart. Granulomas are a specific form of inflammation in which histiocytes dominate.
What is Darier-Roussy sarcoidosis?
Darier-Roussy sarcoidosis is a rare subcutaneous form of sarcoidosis. The Darier-Roussy type of sarcoidosis is characterised by firm subcutaneous nodules on the trunk and extremities. These may occur before, at the same time, or after sarcoidosis has affected other organs. It was originally described in 1904 by Ferdinand-Jean Darier, a French dermatologist, and Gustave Roussy, a Swiss-French pathologist.
Darier-Roussy disease has also sometimes been used to describe other conditions in which there are subcutaneous nodules.
Who gets Darier-Roussy sarcoidosis?
- Darier-Roussy sarcoidosis affects 1–12% of patients with sarcoidosis.
- The subcutaneous form of sarcoidosis commonly affects both sexes.
- Incidence peaks in the age group from 20–29 years; a second peak is observed for women over 50
- There are genetic and HLA associations
What causes Darier-Roussy sarcoidosis?
Despite intensive investigation, the cause of Darier-Roussy subcutaneous nodules and other forms of cutaneous sarcoidosis is unknown. Sarcoidosis is recognised as a chronic cell-mediated immune response to an unknown antigen, in which activated macrophages and CD4 T-lymphocytes release cytokines that trigger the formation of granulomas.
At least some cases of cutaneous sarcoidosis may be due to an unusual host reaction to one or more infective agents, such as Mycobacterium paratuberculosis, histoplasmosis and other fungi. The subcutaneous nodules of sarcoidosis are not infectious.
What are the clinical features of Darier-Roussy sarcoidosis?
Typically the patient with Darier-Roussy disease presents with few to numerous 0.3–0.5 cm deep-seated, non-tender red or skin-coloured nodules on the trunk and extremities.
- Nodules are most commonly located on the upper extremities and trunk
- On the forearms, lesions often coalesce to form linear bands
- The number of lesions ranges between 1 and 100
- The average size of a nodule is 0.5 to 2 cm
- They may be asymptomatic or mildly tender
Features of systemic sarcoidosis may also be present, such as:
- Fever, malaise and weight loss
- Cough and breathlessness
- Enlarged liver and spleen
- Excessive excretion of calcium in urine associated with kidney stones
- Irregular heartbeat and heart failure
Reported associations with other autoimmune disorders include:
- Pernicious anaemia
- Autoimmune thyroiditis
How is the diagnosis of Darier-Roussy sarcoidosis made?
Sarcoidosis is diagnosed after taking a careful history, performing a full physical and ophthalmologic examination, and excluding tuberculosis.
Skin biopsy is confirmatory, showing sarcoidal or epithelioid granuloma. These are characterised by:
- Multinucleated giant cells
- Epitheliod histiocytes
- Mature macrophages
- Sparse subcutaneous CD4 T-cell lymphocytes
The absence of a dense lymphocytic infiltrate (such as in the granuloma of tuberculosis) has led to the use of the term “naked granuloma”.
Chest X-ray and high-resolution CT chest may show enlarged hilar lymph nodes and opacities within the lungs, and lung function tests may reveal restrictive lung disease. CT scan or MRI may also show:
- Swelling of brain
- Enlarged liver
- Interstitial granulomatous nephritis
Blood tests may reveal:
- Renal impairment
- Elevated alkaline phosphatase
- Elevated calcium
- Low lymphocyte count, haemoglobin (haemolytic pattern), low platelets
- Elevated serum angiotensin-converting enzyme
Urine 24-hour collection may detect calcium and protein excretion.
An eye examination may reveal:
What is the treatment of Darier-Roussy sarcoidosis?
It is not always necessary to treat subcutaneous sarcoidosis, especially if it is not symptomatic. When required for skin or systemic symptoms, treatment may include:
Subcutaneous sarcoidosis has been reported to have had a varied response to treatment with:
- Nonsteroidal anti-inflammatory drugs
- Intralesional steroids
- Potassium iodide
What is the outlook for a patient with Darier-Roussy sarcoidosis?
Prognosis is variable. The sarcoid nodules may resolve spontaneously within 1–2 years or persist for decades. The presence and extent of systemic sarcoidosis may influence the long-term outlook.