Introduccion : Anaplasma phagocytophilum es una bacteria intracitoplasmatica obligada que pertenece al orden Rickettsiales, reconocido como causante de enfermedad en humanos. Pacientes sintomaticos reportan exposicion a las garrapatas (vector) una o dos semanas antes del inicio de la enfermedad. Presentan una enfermedad febril, no obstante el rango clinico se extiende desde infeccion asintomatica hasta enfermedad fatal. Caso clinico: paciente masculino con cuadro febril prolongado. Pruebas negativas en la busqueda de hepatitis, paludismo, dengue, leptospirosis y enfermedad tifoidea. En el extendido de sangre periferica, con tincion de Wright se encontraron granulocitos con vacuolas intracitoplasmaticas llamadas morulas (microcolonias de Anaplasma phagocytophilum). La impresion diagnostica fue Anaplasmosis Humana Granulocitica (AHG). Se realizo tratamiento con tetraciclina presentandose buena evolucion. Conclusion: la AHG debe ser una entidad a tener presente en los pacientes con cuadro febril prolongado. Se debe obtener una historia clinica detallada buscando la exposicion a garrapatas. Es importante el diagnostico temprano, establecer las diferencias con otras infecciones similares y aplicar prontamente la antibioticoterapia indicada. Rev.cienc.biomed. 2013;4(1):165-169 PALABRAS CLAVE Ehrlichiosis; Enfermedades Transmisibles Emergentes; Anaplasma phagocytophilum; Ixodes. SUMMARY Introduction: Anaplasma phagocytophilum is an obligatory intracytoplasmatic bacteria that belong to Rickettsiales order and that has been recognized as a cause of human disease. Most of symptomatic patients report exposure to ticks (vector) one or two weeks before the beginning of the disease. They present a febrile disease, however the clinical status extends since asymptomatic infection until fatal disease. Clinical case: Male patient with prolonged fever and with negative proofs in the search of hepatitis, malaria, dengue, leptospirosis and typhoid disease. In the peripheral blood smear with Wright’s stain, there were found granulocytes with intracytoplasmatic vacuoles called morulae (microcolonies of Anaplasma phagocytophilum ). Diagnostic impression was Human Granulocytic Anaplasmosis (HGA). Treatment with tetracycline was done and good evolution was reported. Conclusion: HGA should be a disease to have present in patients with prolonged febrile profile. A detailed clinical history with information about exposure to ticks should be gotten. It is important an early diagnosis to establish the differences with other similar infections and to apply promptly indicated antibiotic therapy. Rev.cienc.biomed.2013;4(1):165-169 KEYWORDS Ehrlichioses; Communicable Diseases, Emerging; Anaplasma phagocytophilum; Ixodes.