Recurrent lymphangitic cellulitis syndrome: A quintessential example of an immunocompromised district.

Recurrent lymphangitic cellulitis syndrome (RLCS) occurs when a disordered lymphatic system renders a leg vulnerable to recurrent infection. The underlying immunologic defect is the result of accidental or iatrogenic penetrating wounds on the medial aspect of the thigh or lower limb overlying the greater saphenous vein, because the primary lymphatic drainage vessels are adjacent to this structure. Cracking/fissuring of the skin associated with chronic fungal infection of the feet ("athlete's foot"), most commonly mixed bacterial/fungal interdigital involvement, provides a portal of entry for opportunistic organisms. Bacteria and their products are cleared more slowly in the lymphatic-disrupted and therefore immunologically impaired limb, producing broad areas of dermatitis and around the scars quite distinct from other forms of superficial infection. This rarely develop in otherwise normal limbs. The dermatitis of RLCS and its systemic effects clear with antibiotics but recur intermittently until the tinea pedis is eradicated. The contralateral limb with normal lymphatic structures never develops clinical evidence of infection even though bilateral tinea infection is almost always present. This confirms the central role of an anatomically induced immunocompromised district (ICD) in this syndrome.

The sarcoidal granuloma: A unifying hypothesis for an enigmatic response.

Although the cause of sarcoidosis is unknown, there is growing support for the concept that sarcoidal granulomas result from a hypersensitivity reaction producing a nonspecific response to an extrinsic or intrinsic (autoimmune) antigen in genetically susceptible individuals. The immune milieu associated with these antigens, localized in a specific cutaneous area, produces a variant of Ruocco's "immunocompromised district." This may explain the predilection for sarcoidal granulomas in association with foreign bodies, tattoos, herpes zoster-affected dermatomes, and scars. Similar antigenic stimulation produces sarcoidal granulomas surrounding internal tumors. Finally, systemic sarcoidosis, as manifested by hilar adenopathy, may reflect the lymphatic spread of foreign antigens.

Tattoo and vaccination sites: Possible nest for opportunistic infections, tumors, and dysimmune reactions.

Tattoos have gained worldwide popularity in recent years, and vaccinations are universal preventive measures designed to minimize morbidity associated with specific pathogens. Both dermal tattoos and vaccine injections may alter local immune responses, creating an immunocompromised district on or near the site of placement. This can lead to the development of opportunistic infections, benign and malignant tumors, and local dysimmune reactions. With regard to tattoos, a predominance of warts among a variety of opportunistic infections has been reported. These warts appear to result from a local immune dysregulation rather than from direct inoculation or coincidence. A variety of tumors including basal and squamous cell carcinomas, keratoacanthomas, and malignant melanoma also have been reported in association with tattoos. Granulomatous, lichenoid, and pseudolymphomatous reactions represent the most common dysimmune reactions. Vaccination sites similarly provide a setting for both benign and malignant tumors. Frequent reports of dermatofibrosarcoma protuberans would be unlikely to result from coincidence. Granuloma annulare and pseudolymphomatous reactions are relatively common dysimmune reactions.

Local reactions to imiquimod in the treatment of basal cell carcinoma.

Basal cell carcinoma (BCC) is the most common form of skin cancer. The most commonly utilized surgical therapies for BCC are curettage and electrodesiccation (E and C) and surgical excision. Whereas surgical modalities have acceptable levels of morbidity and a high cure rate, effective non-invasive topical medical treatments of BCC are of great interest. Imiquimod is FDA approved for the treatment of superficial BCC (sBCC), actinic keratoses, and genital warts. There are several situations in which imiquimod is commonly utilized. Patients with multiple or large sBCCs may wish to avoid surgical approaches more likely to be complicated by scarring. We have also found imiquimod to be useful in elderly patients with marginal involvement of nodular BCC when the patient wishes to avoid additional surgery. Imiquimod is also useful when sBCC recurs following surgical treatments such as electrodessication and currettage and when sBCC occurs in areas that heal poorly after surgery. It is essential for physicians to explain to patients that an exuberant skin reaction is a positive indication of treatment success. Using clinical images to demonstrate the range of possible local reactions may be more effective than verbal descriptions. This minimizes the potential for premature discontinuation of therapy by patients.