We report here the case of a 48-year-old Japanese woman showing plaque-forming scattered indurative papules on her face, buttock and extremities. Histological examination revealed a large amount of interstitial mucin deposition, and negative direct immunofluorescence was observed. The provocative phototesting reproduced the skin lesion, and the patient was diagnosed with lupus erythematosus tumidus (LET). A review of ten LET cases previously reported in Japan revealed that all of these cases had clinicopathological features similar to those reported for European cases, although not all of the former fully satisfied the European criteria.

We report here the case of a 48-year-old Japanese woman showing plaque-forming scattered indurative papules on her face, buttock and extremities. Histological examination revealed a large amount of interstitial mucin deposition, and negative direct immunofluorescence was observed. The provocative phototesting reproduced the skin lesion, and the patient was diagnosed with lupus erythematosus tumidus (LET). A review of ten LET cases previously reported in Japan revealed that all of these cases had clinicopathological features similar to those reported for European cases, although not all of the former fully satisfied the European criteria.

Objectives: Blau syndrome is a distinct class of autoinflammatory syndrome presenting with early-onset systemic granulomatosis. Blau syndrome-causing NOD2 mutations located in the central nucleotide-oligomerization domain induce ligand-independent basal NF-κB activation in an in vitro reporter assay. However, the precise role of this signaling on granuloma formation has not yet been clarified. Methods: Blau syndrome-causing NOD2 mutations were introduced into human monocytic THP-1 cells, and their morphological and molecular changes from parental cells were analyzed. Identified molecules with altered expression were examined in the patient’s lesional skin by immunostaining. Results: Although the production of proinflammatory cytokines was not altered without stimulation, mutant NOD2-expressing THP-1 cells attached persistently to the culture plate after stimulation with phorbol myristate acetate. Sustained surface ICAM-1 expression was observed in association with this phenomenon, but neither persistent ICAM-1 mRNA expression nor impaired ADAM17 mRNA expression was revealed. However, the transient induction of PDGF-B mRNA expression was specifically observed in stimulated THP-1 derivatives. In the granulomatous skin lesion of a Blau syndrome patient, ICAM-1 and PDGF-B were positively immunostained in NOD2-expressing giant cells. Conclusions: Sustained surface ICAM-1 expression and transient PDGF-B production by newly differentiating macrophages harboring mutant NOD2 might play a role in granuloma formation in Blau syndrome.