La Hemoglobinuria Paroxistica Nocturna, HPN, es una causa poco frecuente de pancitopenia, con una incidencia aproximada de 1/100.000 personas; sin embargo, debe ser tenida en cuenta por el impacto que puede provocar en los pacientes, llevandolos incluso hasta la muerte. Este es el caso de un varon de 26 anos, que presenta un cuadro de tres anos de evolucion con sintomas de curso intermitente, consistente en disnea, fiebre, astenia, adinamia, dolor abdominal, sangrado gingival, epistaxis, orinas hipercoloreadasintermitentes. Al examen fisico se encuentra palido, tinte icterico, petequias. Habia consultado en los ultimos tres anos por cuadros similares, acompanados de episodios infecciosos. Durante el ultimo cuadro presento hemoglobina de 4,7 g/dL, hematocrito de 14%, leucocitos de 200xmm3, plaquetas de 1000xmm3, reticulocitos4%, Test de Coombs negativo. El trastorno basico de la emoglobinuria Paroxistica Nocturna HPN responsable de la pancitopenia, es la sensibilidad de las celulas hematologicas al complemento, causando lisis celular. Esta patologia tiene varias formas de manifestacion, una de las cuales cursan con signos de hemolisis y falla medular. Su trayectoria es variable, con remisiones y exacerbaciones, o causando la muerte poco tiempo despues del diagnostico dependiendo del numero de celulas afectadas y se establece con la prueba de Ham,la prueba de la sacarosa o la citometria de flujo. Debido a los antecedentes de infecciones repetidas, sangrados, petequias yresultados de laboratorio, se enfoca como una posible falla medular, se formulan recomendaciones para su diagnostico bajo la sospecha de una HPN y se solicita Test de Ham.AbstractThe Paroxysmal Nocturnal Hemoglobinuria is an infrequent cause of pancytopenia; although it has an approximate incidence of 1/100.000 people, it always should to be taken into account due the possible consequences in a patient’s health. PNH could be fatal in some patients. This case is a 26 years old man that has been having for the last three years on and off symptoms like dyspnea, fever, asthenia,abdominal pain, gingival hemorrhage, epistaxis, hypercolored urine intermittently. In the physical exam we have a pale patient, slightly jaundiced and with petechiae. The patient has been going to the doctor’s office for the last three years with similar concerns, accompanied with infectious episodes. The last episode, the patientpresented with an hemoglobin of 4,7 g/dL, a hematocrit of 14%, leucocytes of 200 x mm3, platelets of 1000 x mm3, reticulocytes of 4%, and a negative Coombs test. The principal cause of pancytopenia in PNH is the sensitivity of the blood cells to complement that cause cell lysis. This pathology has different forms of presentation: One of the forms presents with signs of hemolysis and bone marrow failure. This pathology has a variable course with constant exacerbations and remissions, or causing death little time after the diagnosis depending on the number of affected cells. The diagnosis is made with theHam test, the saccharose test or flow cytometry. Because of the history of frequent infections, hemorrhages, petechiae and the laboratory results, he is taken as a patient with a possible bone marrow failure. Recommendations are made for his possible diagnosis of PNH and a Ham test is ordered.KeyWords: Anemia; Pancytopenia; Paroxysmal Nocturnal Hemoglobinuria