RT Book, Section
A1 Prchal, Josef T.
A2 Kaushansky, Kenneth
A2 Prchal, Josef T.
A2 Burns, Linda J.
A2 Lichtman, Marshall A.
A2 Levi, Marcel
A2 Linch, David C.
SR Print(0)
ID 1178742181
T1 Methemoglobinemia and Other Dyshemoglobinemias
T2 Williams Hematology, 10e
YR 2021
FD 2021
PB McGraw-Hill Education
PP New York, NY
SN 9781260464122
LK hemonc.mhmedical.com/content.aspx?aid=1178742181
RD 2024/04/19
AB SUMMARYMethemoglobin  is  a  metalloprotein,  in  which  the  iron  in  the  heme  group  is  in  the  Fe3+(ferric),  not  the  Fe2+(ferrous),  state  of  normal  hemoglobin  (Hb).  Methemoglobinemia  occurs  because  of  either  increased  production  of  oxidized  Hb  due  to  exposure  to  environmental  agents  or  diminished  reduction  of  oxidized  Hb  because  of  underlying  germline  mutations.  Cyanosis  occurs  when  methemoglobin  exceeds  15g/L;  in  comparison,  cyanosis  is  discernible  with  deoxyhemoglobin  at  40g/L  and  sulfhemoglobin  at  5g/L.  Hb  can  also  bind  carbon  monoxide  and  nitric  oxide,  resulting  in  the  formation  of  carboxyhemoglobin  and  nitrosohemoglobin.  Sulfhemoglobinemia  occurs  because  of  occupational  exposure  to  sulfa  compounds  or  exposure  to  oxidants.  These  modified  Hbs  are  known  as  dyshemoglobins.  Depending  on  the  severity,  the  presence  of  dyshemoglobins  can  result  in  varying  degree  of  clinical  manifestations.  Prompt  diagnosis  is  the  key  to  the  specific  treatment.