Introduction - sarcoidosis
Introduction - Darier-Roussy sarcoidosis
Demographics
Causes
Clinical features
Diagnosis
Treatment
Outlook
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.
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.
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.
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.
Features of systemic sarcoidosis may also be present, such as:
Reported associations with other autoimmune disorders include:
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:
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:
Blood tests may reveal:
Urine 24-hour collection may detect calcium and protein excretion.
An eye examination may reveal:
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:
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.
