A 68-year-old Caucasian male was referred to the Rheumatology Department with the clinical suspicion of adult-onset Still’s disease (AOSD) since the patient had fever, high inflammatory markers, a rash and an extensive work up had excluded infectious or neoplastic causes.  Twelve months ago, the patient first developed a non-pruritic rash on his torso and arms that recurred frequently. During the last few months, the patient developed fever and significant weight loss, therefore a series of investigations was performed. Lab tests revealed an ESR of 130mm/h, a 15-fold elevation of CRP, leucocytosis with normal complement levels, and no autoantibodies. A full body CT and temporal artery biopsy were unremarkable. An IgMκ monoclonal gammopathy was found and the patient was admitted to hospital for further investigations with the initial suspicion being a hematologic malignancy. An extensive evaluation including bone marrow biopsy and PET/CT ruled out lymphomas, myeloproliferative disorders or plasma cell dyscrasias whereas a thorough work up for infectious diseases was negative. When we first evaluated the patient, we noticed that the rash had urticaria-like features and was not compatible with AOSD (Figure 1A). Ferritin levels were within normal limits despite the robust inflammatory response making the diagnosis of AOSD even more unlikely. Since the rash was the first sign of the disease, a full review of the patient’s record was performed in collaboration with dermatology colleagues. The combination of an urticarial rash, IgMκ monoclonal gammopathy, fever and inflammatory response pointed towards Schnitzler’s syndrome, a rare but potentially underdiagnosed, autoinflammatory disease of unknown aetiology. Notably, extensive osteosclerotic lesions in the pelvis were noted on imaging, also suggestive of the disease (Figure 1B). The patient started treatment with anakinra and exhibited a dramatic response with disappearance of skin lesions, and normalization of inflammatory markers.  

Figure 1. (a) Skin rash with urticaria-like features. (b) Reformatted coronal oblique CT image (bone windows) at the level of the sacroiliac joints. Centred at the left ilium, there is a predominantly sclerotic lesion with lace-like pattern, narrow zone of transition and relatively well-defined margins (arrows). Note the presence of a similar smaller lesion on the right iliac bone (arrowheads).

CONFLICT OF INTEREST

The authors declare no conflict of interest.

FUNDING

This work was not funded by any source.