Erythema Nodosum: Clinicopathologic Correlations and Their Use in Differential Diagnosis

PURPOSE: Typically, a diagnosis of erythema nodosum (EN) is based on clinical features. However, other diseases manifest with inflammatory nodules of the lower limbs in addition to EN, such as the EN-like lesions of Behcet's disease (BD). The purpose of this retrospective study was to investigate the frequency of histologically proven EN among diseases diagnosed clinically as EN, to determine underlying causes of EN, and to compare clinical and histologic features between EN and other diseases. PATIENTS AND METHODS: We selected 99 patients diagnosed clinically with EN and performed skin biopsies. All pathologic slides were evaluated and diagnosed; and after histologic diagnoses were made we reviewed the patients' medical records. RESULTS: Among the 99 patients diagnosed clinically with EN, 47 were biopsy-verified EN. The EN-like lesions of BD and nodular vasculitis were both in the primary differential diagnosis of EN. No definite difference in clinical features exists among these three diseases. Histologically, EN demonstrated septal panniculitis in the majority of patients. Lobular panniculitis was frequently observed in NV, and mixed or mostly lobular panniculitis was observed in the EN-like lesion. Vasculitis was rarely observed in EN; however lymphocytic vasculitis was observed frequently in EN-like lesions and neutrophilic vasculitis was observed in NV. The frequency of granulomatous inflammation was highest in NV. Some cases of patients with typical BD demonstrated classic EN lesions. CONSLUSION: It was extremely difficult to clinically differentiate EN from EN-like lesions or NV. We feel skin biopsy is mandatory for the diagnosis of lower extremity erythematous nodular lesions.

A Case of Erythema Nodosum-like leukemia cutis / 대한피부과학회지

We have encountered a rare case of erythema nodosum-like leukemia cutis associated with acute myelocytic leukemia(AML) in a 57-year-old male. He was in good health until about 2 weeks prior to admission, when the systemic symptoms of high fever, anorexia, general weakness and malaise, and subcutaneous nodules developed. The nodules were multiple, red and noted bilaterally on the pretibial areas. Histological findings of his skin lesions showed diffuse cellular infiltrates intermingled with leukemic cells predominantly involving the adipose tissues. The cells displayed negative stainirig to antibodies CD3 and CD20, but positive staining to LCA. The diagnosis of AML(M4) was made by blood and bone marrow studies. He had a rapid downhill course and was discharged after 2 weeks of admission, with no anti-cancer chemotherapy.