Neutropenia (scaderea numarului de neutrofile): se clasifica in usoara (1000-1500/µL), moderata (500-1000/µL) si severa (<500/µL);

Agranulocitoza reprezinta o forma severa de neutropenie cu absenta totala a neutrofilelor circulante. Neutropenia severa se asociaza cu risc crescut de infectii.

Cauze de neutropenie:
Infectii bacteriene severe, septicemie in special cu bacterii Gram negative; infectii virale: neutropenia survine in primele 1-2 zile si persista 3-7 zile, de obicei fara semnificatie clinica; neutropenie prelungita poate aparea in infectii cu virusul hepatitic B, virusul Epstein-Barr, HIV; infectii cu protozoare (malarie), fungi, rickettsii.

Substante chimice, toxice si medicamente: aminopirina, penicilina, aur, quinidina, antibiotice β-lactamice, carbamazepina, acid valproic, arseniu, mercur, fenilbutazona, indometacin, ibuprofen, acid acetilsalicilic, barbiturice, mesalazina, fenotiazine, imipramin, desipramin, diazepam, clordiazepoxid, meprobamat, haloperidol, fenitoin, etosuximid, carbamazepin, lamotrigin, tiouracil, metimazol, carbimazol, tiocianat,  procainamida, captopril, propranolol, hidralazina, metildopa, diazoxid, nifedipin, propafenona, ticlopidina, enalapril, amiodarona, quinidina, cimetidina, ranitidina, famotidina, cefalosporine, vancomicina, cloramfenicol, gentamicina, clindamicina, doxiciclina, flucitozina, nitrofurantoin, griseofulvin, metronidazol, rifampicina, izoniazida, streptomicina, mebendazol, pirimetamina, levamisol, sulfonamide, etambutol, ciprofloxacin, trimetoprim, imipenem, clorochin, hidroxiclorochin, quinacrin, dapsona, zidovudina, aciclovir, ganciclovir, terbinafina,clorpropamid, tolbutamid, acid etacrinic, acetazolamida, tiazide, spironolactona, alopurinol, colchicina, bezafibrat, tamoxifen, penicilamina, acid retinoic, metoclopramid, Rauwolfia, etanol, imunoglobuline intravenoase, omeprazol, levodopa.

Neutropenia nutritionala: casexie, stari debilitante, anorexie nervoasa, deficit de vitamina B12 si folat, deficit de cupru.
Neutropenia imuna (prezenta de anticorpi anti-neutrofile).

Chimioterapia in cancer, tratamentul cu metotrexat in artrita reumatoida.

Boli hematopoietice: leucemia (aleucemica), anemia aplastica.
Neutropenia congenitala severa (sindromul Kostmann).
Boli metabolice: glicogenoza tip Ib, metilmalonic acidemia.

Neutrofilia: >8000/µL sau 8×109/L:

Infectii bacteriene acute localizate si generalizate.
Infectii virale, fungice si parazitare.
Sepsis neonatal.
Boli inflamatorii cronice: vasculite, artrita reumatoida, bronsita, colita, dermatita, pielonefrita, pancreatita.
Boli metabolice: coma diabetica, coma uremica, coma hepatica, atacul acut de guta, eclampsia, tireotoxicoza.
Necroza tisulara: arsuri, infarct miocardic.
Toxice si medicamente: corticosteroizi, plumb, mercur, monoxid de carbon, digitala, veninuri.
Hemoragia acuta (neutrofilie pana la 25000/µL in a 3a-a 5a zi), proceduri chirurgicale majore, anemia hemolitica, postsplenectomie.
Tumori maligne, in special carcinoame (gastrointestinal, pulmonar): neutrofilia apare ca urmare a reactiei inflamatorii, necrozei tumorale, producerii de factori de crestere granulopoietici de catre tumora.
Boli mieloproliferative cronice (leucemia mieloida cronica, policitemia vera, trombocitemia esentiala, metaplazia mieloida cu mielofibroza).