BACKGROUND: Polyangiitis overlap syndrome (POS),a systemic vasculitis not classifiable into well-defined syndromes, is  diagnosed based on combined characteristics of two or more primary systemic vasculitides, such as Takayasu arteritis  and anti-neutrophil cytoplasmic antibody (ANCA)-associated  vasculitis  (AAV), but not two AAVs. Our objective is to   present such,   with associated  multiple  infections.
CASE: A  25-year-old  Filipino  female  had  six  years  of  recurrent  purpura,  debilitating  joint  pains,  hemoptysis,  rhinorrhea, epistaxis, eye redness, dyspnea,  and  abdominal  cramps. She was cachectic, had oral ulcers, bibasal  crackles,  polyarthritis,  and  generalized  purpura.   Work-up   showed   anemia,   eosinophilia  excluding   parasitism,   elevated inflammatory markers, and  positive cytoplasmic (c)-ANCA and anti-proteinase 3. There   was   chronic sinusitis on rigid rhinoscopy, middle to lower lung field  interstitial   infiltrates   on   radiographs, pulmonary vasculitis   on  chest   CT,   moderate pulmonary hypertension on  echocardiography,  but  normal  spirometry.  Skin  biopsy  showed  leukocytoclastic vasculitis without  necrotizing  granulomas.Serology showed chronic hepatitis B infection.   Pseudomonas  aeruginosa and  methicillin-resistant Staphylococcus  aureus  grew  from  bronchial  washings and   nasal   swabs,   respectively. ASO titer was high. Human  immunodeficiency  virus  infection  was  ruled  out.  She   was   diagnosed with POS,with features of two AAVs- limited granulomatosis   with   polyangiitis   (GPA)   and   Churg-Strauss   syndrome  (CSS), associated with   multiple  infections,   and  was  given naproxen and culture-guided   antibiotics  (ciprofloxacin, clindamycin, penicillin),with partial resolution of symptoms.  Prednisone   10  mg once  a  day (OD)  was   started  two weeks   after hepatitis B reactivation prophylaxis   with   lamivudine 100mg OD. Complete   resolution of skin lesions and upper airway symptoms and    inflammatory  marker  improvement  were observed after 12  weeks. She is  maintained on prednisone   5.0   mg   daily.
CONCLUSION AND RECOMMENDATIONS: This   is   the   first   reported   case   of   POS   involving   two   AAVs   -   limited   GPA   and   incomplete   CSS,   associated   with   multiple   pathogens.Identifying  POS  is  important;    inability to  classify patients  into well-recognized  vasculitic  syndromes  delays  treatment.  The  infections likely  perpetuated   the   vasculitis,  and  both antimicrobials  and  immunosuppression were  necessary  to  induce   disease   remission