BADAS is a non-infectious neutrophilic dermatosis with prominent of features of rashes and joint pain. Typical rashes are red spots with diameter of 3–10 mm and vague boundaries. The rashes gradually harden in the following 1 or 2 days and turn to papulopustule with diameter of 2–4 mm. The process of this disease could last for 2–8 days and showed as a self-limited process (Patton et al. 2009; Slater et al. 2004; Kawakami et al. 2006). The rashes are mainly distributed on the body and limbs (Jorizzo et al. 1983), and they may be featured by pruritus, pain or no subjective symptom (Slater et al. 2004). Polyarthritis may be involved in patients which had peripheral joints like IP joints and wrist joints, however, but there is no imageological change, joint destruction or deformity (Utsinger 1980). Laboratory indexes such as RF, immune globulin and uric acid are all within normal limits, however, some patients may have elevated cryoglobulin (Patton et al. 2009). In microbiological examination, both of blood culture and rash fester culture results are negative (Truchuelo et al. 2013). The dermal pathology of BADAS is usually the same as acute febrile neutrophilic dermatosis (SWEET) syndrome. It mainly shows infiltration of mature neutrophile granulocyte in dermis and sometimes edema of dermal papilla. It had no fibrinoid necrosis or blood vessel infarct, which is the main difference from leukocytoclastic vasculitis (Patton et al. 2009; Ashok and Kiely 2007). However, other research showed that the dermal pathology changes with the development of the disease is not an essential condition for diagnosing the BADAS (Patton et al. 2009). In the course of clinical diagnosis and treatment, BADAS also must be distinguished from extra-intestinal manifestations of inflammatory bowel disease (Adams and Eksteen 2006; Trikudanathan et al. 2012; Marineaţă et al. 2014; Brown et al. 2015).
As the cause is not clear, it is now generally accepted that it is an abnormal immune response of residual intestine after intestinal survey or abnormal intestine of inflammatory bowel disease to the bacterial overgrowth. SIBO is defined as nonpathogenic bacteria increase over 105cfuin 1 ml of small intestine content. Due to the lack of specific symptoms, SIBO is often misdiagnosed. In fact, SIBO occurrence is fairly frequent. SIBO might present in more than 60 % patients with abdominal pain (Siniewicz-Luzenczyk et al. 2015). In systemic sclerosis, 38 % patientswith intestinal complaints were diagnosed with SIBO (Tauber et al. 2014). The formation of immune complex, access to blood and deposition in tissues and organs are crucial in the occurrence of disease which could induce various related clinical symptoms (Slater et al. 2004; Utsinger 1980; Dicken 1986; Jorizzo et al. 1984) and this theory can be indirectly proved by the curative effect of antibiotics and glucocorticoid to the disease. Glucocorticoid is as the main medicine for this disease and antibiotics (metronidazole, tetracycline and sulfonamides) are also used with different effects. Resuming the normal anatomy of intestine or curing potential gastrointestinal disease also has certain mitigative effect (Ashok and Kiely 2007).
About 20 % of patients of jejunoileum bypass bariatric surgery are likely to have the symptoms of rash or joint pain (Ely 1980). Other non-bypass surgery or disease of digestive tract such as inflammatory bowel disease has had already been continuously reported, which is secondary to the BADAS (Cox and Palmer 2003; Patton et al. 2009). In our case, the clinical manifestation and dermal pathology of rashes are the same with those diseases mentioned above, however, there is no intestinal surgery, nor any evidence of inflammatory bowel disease. Only the hydrogen-methane breath test with lactulose as the substrate indicates SIBO. The disease may not merely occur among patients of jejuno-ileum bypass bariatric surgery and inflammatory bowel disease as mentioned in previous literature. Immuno-inflammatory response to bacterial antigen may be caused by any factors which caused the overgrowth of intestinal bacteria, mediate formation of immune complex and hence induce the clinical symptoms of BADAS. Therefore, whether the patients had specific digestive system surgery or medical history, as organic or functional factor which may cause intestinal bacterial overgrowth should be taken into consideration during the clinical diagnosis of physician. Patient with only SIBO, non-intestinal bypass road and non-inflammatory bowel disease could also be diagnosed as BADAS.