A Case of Pyoderma Gangrenosum as Skin Manifestation of SAPHO Syndrome in an IBD Patient

A 39 year old Caucasian male with a history of rectosigmoid ulcerative colitis (UC) was transferred to our hospital with joint pain, skin lesions, and fevers. He was initially diagnosed with UC in 2015 after experiencing hematochezia, abdominal pain and weight loss. He was started on budesonide and oral mesalamines. Given his refractory symptoms, he was started on adalimumab. However he developed rapid formation of high antibody levels, so he was transitioned to vedolizumab and azathioprine a year later. Until the time of presentation, he reported good control of his symptoms. He presented to the outside hospital in June 2018 with chest and back pain. In addition, he reported painful skin “pimples” throughout his chest, back and axilla which began to express pus. I&D's were performed of multiple lesions with purulent drainage; however they increased in size after incision. MRI showed findings concerning for osteomyelitis involving T4-6 and L2 vertebral bodies. He was placed on broad spectrum antibiotics, and his azathioprine was held. Despite antibiotic therapy, he developed fevers and was transferred to our hospital. Upon arrival, physical examination revealed multiple crusted, erythematous 1 cm pustules on his sternum (Fig. 1) and back. There was also a 6x3 cm ulcerated plaque on his left buttock with fibrinous necrotic material surrounded by an indurated rim of gray tissue (Fig. 2). In addition, there was a large ulcerated wound with necrotic center with surrounding violaceous erythema in his right axilla. A shave biopsy of his left buttock revealed a dense neutrophilic infiltrate throughout the dermis. Upon further review of imaging, osteomyelitis was ruled out but there was concern for osteitis (Fig. 3). Based on the clinical and histopathological findings, the diagnosis of SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome was made in addition to pyoderma gangrenosum (PG). Antibiotics were discontinued, and he was started on IV steroids with resolution of his fever and improvement in his skin lesions.2055_A Figure 1. Subcutaneous 1 cm pustule with surrounding inflammation and central incision from prior I&D2055_B Figure 2. 6x3 cm ulcerated plaque on his left buttock with fibrinous necrotic material surrounded by an indurated rim of gray tissue with erythema2055_C Figure 3. Pattern of marrow edema and enhancement in T4-T6 and L2, without disc or epidural enhancement, consistent with osteitis.SAPHO syndrome is a rare disease, with an estimated prevalence of 1:10,000 in the Caucasian population. There are only a few cases of PG presenting as a skin manifestation of SAPHO syndrome. This is a rare case highlighting the association between SAPHO syndrome and PG in a patient with well-controlled IBD. Further investigation is warranted regarding the overlap of these conditions and its correlation with IBD.