Among lymphadenitis and abscess categories, there were four cases of undefined immunodeficiency, two cases of chronic granulomatous disease (CGD), one case of severe combined immunodeficiency (SCID), one case of hemophagocytic lymphohistiocytosis, and one case of myeloid differentiation primary response 88 (MyD88). The gene discussed is MYD88; the disease is lymphadenitis.