Urticarial papules and plaques on the trunk

Discussion

Neutrophilic eccrine hidradenitis (NEH) is a rare condition with a highly variable clinical presentation. Lesions range from erythematous papules to indurated nodules and plaques of varying sizes. There may be associated pigmentary or purpuric change. The lesions are usually asymptomatic, but may be pruritic or tender. Common sites of involvement are the trunk and upper limbs. Fever is often associated.[1],[2] The diversity of clinical presentations can mimic a range of other conditions including Sweets syndrome, urticarial vasculitis, disseminated bacterial/fungal infection and leukemic infiltrates.[3]

The characteristic histological features of NEH generally allow the diagnosis to be made. These are vacuolar degenerative changes and necrosis within the secretory cells of the eccrine sweat glands, with a surrounding dense, predominantly neutrophilic infiltrate in the deep dermis. The neutrophilic infiltrate may be mild in patients with a neutropenia. Diffuse dermal edema with perivascular infiltrate consisting of lymphocytes, neutrophils, macrophages and eosinophils may also be seen. Features like apocrine involvement and epidermal lichenoid tissue reaction can also be seen.[3]

The etiology of NEH is unclear; however, there are two theories regarding its pathogenesis. The first suggests that NEH belongs to the spectrum of neutrophilic dermatoses, with primary involvement of the eccrine glands. The other theory postulates that the infiltrate in NEH is secondary to drug-induced eccrine gland changes. Several studies have suggested that NEH belongs to the spectrum of drug-induced eccrine gland changes that include syringosquamous metaplasia and eccrine necrosis. There are several reports of chemotherapy-related eruptions in which histological examination showed isolated necrosis or syringometaplasia of the eccrine coils without neutrophilic infiltration.[4],[5]

Different kinds of agents have been implicated as etiologies. Cytarabine and bleomycin are the two most often associated with NEH, but the list also includes cyclophosphamide, topotecan, methotrexate, granulocyte colony stimulating factor (GCSF), lomustine, doxorubicinm bleomycin, 5-fluorouracil, vinblastine, VAPA-10 and dacarbazine.[3],[4] In these cases, NEH has been considered to represent focal toxicity to the eccrine unit, lying within the spectrum of drug-induced eccrine gland changes.[5] Microorganisms, such as HIV, hepatitis C virus, Serratia, Enterobacter, Staphylococci and Nocardia have also been implicated. Other causes include malignancy alone, reverse transcriptase inhibitors and rheumatologic disease (Behcet′s disease).[6] The diversity of the presentations suggests that NEH represents a cutaneous reaction pattern to a broad spectrum of clinical conditions.[3]

The mainstay of treatment is to withdraw any implicated drug. This is usually sufficient because NEH tends to resolve spontaneously within a few weeks. Due to the sporadic nature of the disease, it has yet to be determined whether prophylactic nonsteroidal anti-inflammatory drugs, corticosteroids or dapsone are helpful in preventing recurrences with subsequent courses of chemotherapy.

Recognition of NEH is important in order to exclude other neutrophilic dermatoses associated with malignancies, such as sepsis and acute febrile neutrophilic dermatoses, which may appear clinically similar. Rapid diagnosis may avert unnecessary changes in therapy to treat conditions which clinically mimic NEH.