John C. Hall MD
When considered singularly, granulomatous diseases are uncommon, but when all of them are considered together, they form a group that is interesting, varied, and ubiquitous.
A granuloma is a focal chronic inflammatory response to tissue injury manifested by a histologic picture of an accumulation and proliferation of leukocytes, principally of the mononuclear type and its family of derivatives, the mononuclear phagocyte system. The immunologic components in granulomatous inflammation originate from cellmediated or -delayed hypersensitivity mechanisms controlled by thymus-dependent lymphocytes (T lymphocytes). Five groups of granulomatous inflammations have been promulgated:
▪ Group 1 is the epithelioid granulomas, which include sarcoidosis, tuberculosis in certain forms, tuberculoid leprosy, tertiary syphilis, zirconium granuloma, beryllium granuloma, mercurial granuloma, and lichen nitidus.
▪ Group 2, histiocytic granulomas, includes lepromatous leprosy, histoplasmosis, and leishmaniasis.
▪ Group 3 is the group of foreign body granulomas, including endogenous products (e.g., hair, fat, keratin), minerals (e.g., tattoos, silica, talc), plant and animal products (e.g., cactus, suture, oil, insect parts), and synthetic agents such as synthetic hair and filler substances.
▪ Group 4 is the necrobiotic/palisading granulomas, such as granuloma annulare, necrobiosis lipoidica, rheumatoid nodule, rheumatic fever nodule, catscratch disease, and lymphogranuloma venereum.
▪ Group 5 is the mixed inflammatory granulomas, including many deep fungal infections such as blastomycosis and sporotrichosis, mycobacterial infections, granuloma inguinale, and chronic granulomatous disease.
Most of these diseases are discussed with their appropriate etiologic classifications in the Dictionary-Index. Two of these granulomatous inflammations are discussed in this chapter: sarcoidosis, which is in group 1, and granuloma annulare, which is in group 4. A classification of granulomas based on etiology is listed in Table 16-1.
Sarcoidosis is an uncommon systemic granulomatous disease of unknown cause that affects the skin, lungs, lymph nodes, liver, spleen, parotid glands, and eyes. Less commonly involved organs that indicate more severe disease include the central nervous system, heart, bones, and upper respiratory tract. Any or all of these organs may be involved with sarcoidal granulomas. Lymphadenopathy is the single most common finding. People of color are affected more often than white patients (14:1). Only the skin manifestations of sarcoidosis are discussed here (Fig. 16-1; see also Fig. 38-15).
Presentation and Characteristics
Cutaneous sarcoidosis is a great mimicker of other skin diseases. Superficial lesions consist of reddish papules, nodules, and plaques that may be multiple or solitary and of varying size and configuration. Annular forms of skin sarcoidosis are common. These superficial lesions usually involve the face, shoulders, and arms. Infiltration of sarcoidal lesions frequently occurs at scar sites. Subcutaneous nodular forms and telangiectatic, ulcerative, erythrodermic, and ichthyosiform types are rare. Sarcoidosis is often associated with a chronic systemic disease.
Central healing can result in atrophy and scarring.
Most cases of sarcoidosis run a chronic but benign course with remissions and exacerbations. Spontaneous “cure” is not unusual. Erythema nodosum is characteristic of acute benign sarcoidosis (see Chapter 12). Lupus pernio (indurated violaceous lesions on the ears, nose, lips, cheeks, and forehead) and plaques are characteristic of chronic, severe, systemic disease. It is seen most often in women and girls of color.
The cause of sarcoidosis is unknown.
TABLE 16-1 ▪ Granulomatous Diseases of the Skin by Etiology