Introduction: Primary immunodeficiencies are genetic disorders of the immune system, which result in a wide variety of clinical manifestations, most often manifest at an early age; and although a large part of these have an autosomal recessive hereditary form; it is not a necessary pattern in its natural history. One way to classify immunodeficiencies is in two categories: 1) the innate system (alterations in complement and phagocytic cells) and 2) adaptive system (including mechanisms of the humoral and cellular system) (Bonilla et al., 2005). However, the most recent classification is that of 2015 proposed by the "International Union of Immunology Societies"; describing nine groups of diseases (Gutierrez Saborido et al., 2016). The wide variety of clinical manifestations and the low prevalence of these make them a challenge for the clinician who needs a high suspicion, where manifestations such as diarrhea is usually variable and this may be of infectious or autoinflammatory cause (Hernandez Martinez et al., 2016). Objective: To present the case of a patient with a primary immunodeficiency, a 2-year-old male patient who started the approach from a seemingly chronic diarrhea without evidence of another manifestacón. Observe in consecutive studies the periodic variation in the levels of Absolute neutrophils which were related to diarrhea. Conclusion: The approach of an immunodeficiency; Whether primary or secondary, it is always a challenge for the general practitioner and for the pediatrician; in this case, from an infectious recurrence and a finding in laboratory studies, the approach is initiated, however many of these clinical pictures are asymptomatic at the beginning or are only a finding at the time of the approach as in the case reviewed, however, was the chronicity of the diarrheic picture that did not suspect the relationship with immunodeficiency.
