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Paper text:
histopathologically , it is a neutrophilic dermatosis which presents as deep purulent ulcers with well - defined and often undermining margins with a violaceous hue .
multiple phenotypes of pyoderma gangrenosum have been described ; ulcerative form is the most common type ( 1 ) .
the most common location of pyoderma gangrenosum is in the lower extremities ( 2 , 3 ) but any part of the body can be involved . in inflammatory bowel disease , pyoderma gangrenosum is reported in about 3% patients in ulcerative colitis and more often in patients with crohn 's disease ( 4 ) . in the general population ,
it has been described both as a cutaneous disorder of uncertain etiology ( 5 ) and a cutaneous manifestation of systemic disorders .
about half of the cases of pyoderma gangrenosum have an associated systemic disorder ( 6 ) .
most common systemic disorders include inflammatory bowel disease , hematologic malignancies , autoimmune arthritis , and vasculitis . as a cutaneous disorder ,
visceral lesions are similar to cutaneous lesions ( sterile neutrophilic infiltration with granuloma formation ) and have been reported in lungs , liver , bone , spleen , major airway , heart , and so on ( 710 ) .
the most likely differential diagnosis is granulomatosis with polyangiitis . in the cases reported here , the patient had no evidence of renal or upper airway involvement and was tested negative for c - anca .
the combination of lack of clinical findings and c - anca make granulomatosis with polyangiitis very unlikely in our patient . as per a literature review performed in 2011 ,
11 cases of pulmonary nodules with or without cavitation have been reported in pyoderma gangrenosum ( 11 ) . reported pulmonary nodules are usually subpleural , unilateral or bilateral , no predilection to upper lobe , may or may not have sterile central caseation leading to cavity formation .
lung biopsies of these lesions show non - specific necrotizing inflammatory granulomas with neutrophilic infiltration ( 11 ) .
a very high recurrence rate is reported ( 312 ) and about 5% of cases are refractory to glucocorticoids that have been successfully treated with cyclosporine a , tacrolimus , or a biological agent ( 13 , 14 ) .
our patient was continued on mesalamine ; oral prednisone was being tapered down without worsening of cutaneous lesions and inflammatory changes in the lung cavity were resolved . in conclusion
based on prior reports of histopathological similarity in skin and lung lesions and response to steroid treatment , pulmonary nodules could be assumed a spectrum of extraintestinal manifestation of ulcerative colitis . in clinical practice ,
granulomatosis with polyangiitis should be considered as differential diagnosis as up to 14% of the patients with granulomatosis with polyangiitis have cutaneous lesions ( 15 ) .
lack of vasculitis in biopsy and immune deposits favor pyoderma gangrenosum , whereas c - anca is highly specific for active granulomatosis with polyangiitis ( 16 ) .
the authors have not received any funding or benefits from industry or elsewhere to conduct this study .
pyoderma gangrenosum is a phenomenon of cutaneous ulceration where etiology is not well understood . 
 about half of the cases have an associated extracutanoeus manifestation or associated systemic diseases 
 . most commonly associated systemic disorders include inflammatory bowel disease , hematologic malignancies , autoimmune arthritis , and vasculitis . 
 we are reporting a case where pyoderma gangrenosum has presenting features for ulcerative colitis .