Hematopoiesis in the bone marrow is regulated by its niche and by immune system cells. These cells are derived from bone marrow precursors and therefore immunological alterations are frequently observed in Myelodysplastic Neoplasia (MN), complex and heterogeneous disease.

description of a clinical case through data collection from HSPE/IAMSPE-SP digital system.

Male, 64 years old, with bipolar disorder and prolonged bicytopenia. In january/21 diagnosed with NM, myelogram: 10% of blasts with dysplastic changes in the 3 series, IPSS-R = 3.8, FISH and karyotype without abnormalities. Submitted to the AZAVIT-ABCDEF protocol (Azacitidine, erythropoietin, filgrastim associated with high dose of vitamin B1, C and D), after signing consent form (Plataforma Brasil-CAAE: 53015421000005463). Evolved with sporadic need for transfusion, in the first year he received 23 packed red blood cells. In July/22 he developed a large, ulcerated lesion with irregular and painful borders on his left leg, after being infected with COVID-19. Anatomopathological: chronic ulcer, without signs of malignancy. Follow-up and clinical evaluation suggested the diagnosis of Pyoderma Gangrenosum (PG). Treatment with high dose of corticosteroids was started, but the psychiatric condition got worse. Replaced by cyclosporine, serum level maintained around 200 ng/mL, we observed slow healing of the ulcer. In NOV/22, he presented a dense and elevated lesion in the nasal fin, computed tomography showed infiltration up to the lacrimal canal. Biopsy compatible with Bowenoid in situ carcinoma (possibly mediated by HPV), with proposal for rhinotomy. It was then decided to immediately withdraw cyclosporine. In the already healed PG region, topical corticosteroids were maintained. There was total regression of the nasal lesion, with control tomography demonstrating slight thickening. A new biopsy showed no neoplastic infiltrate. Despite the suspension of immunosuppression, there was no reactivation of PG. Complete blood count in july/23: Hb = 13.4 g/dL, leukocytes = 4770 (2/62/3/0/30/3) and platelets: 92.000/mm3 and no need for transfusion since july/22. He's in the 27 cycles of the AZAVIT-ABCDEF.

NM is characterized by clonal hematopoiesis, cytopenias and dysplastic cell morphology. Among the few therapeutic options, azacitidine is being used with some benefits. PG is an uncommon neutrophilic dermatosis, but frequent in hematologic malignancies, presents as a painful inflammatory and ulcerative disorder of the skin. Neutrophils are the main actors of innate immunity and within tissues they perform several functions such as phagocytosis, cytokine production, degranulation of soluble antimicrobial substances and production of extracellular neutrophil traps to eliminate pathogens. The use of azacytidine and the Covid-19 infection may have contributed to the exacerbated and prolonged activation of neutrophils, originating PG.

Immunological alterations such as autoimmune thrombocytopenia, vasculitis, PG and Sweet's syndrome are frequent in NM. The rapid recognition of inflammatory processes and the early institution of immunosuppressive treatment have an impact on the outcome of NM. However, the side effects must be weighed due to their severity, in this case the Bowenoid carcinoma.