Although PNH is caused by excessive proliferation of hematopoietic stem cell (HSC) clones with loss of function mutations in phosphatidylinositol N-acetylglucosaminyltransferase subunit A (<i>PIGA</i>) genes, what drives PNH clones to expand remains elusive.<h4>Case description</h4>We present a case of a 26-year-old female who presented with hemolytic anemia, thrombocytopenia, and leukopenia. The gene discussed is PIGA; the disease is Decreased total leukocyte count.