Something intrinsically wrong with the RBC causing it to hemolyze but there’s nothing wrong with the BM (but something intrinsically wrong with the RBC),

and  the  corrective  ret  ct  is  greater  than  3%.    

MAD  –  MC  intrinsic  probs

Membrane   defect   (spherocytosis,   paroxysmal   nocturnal   hemoglobinuria),   Abnormal  Hb  (SC  trait  Dz),  

De5iciency  of  enzyme  (G6PD  def).   1.  Membrane  Defects:

(a)     Spherocytosis:   do   no   see   a   central   area   of   pallor   therefore   must   be   a   spherocyte  and  must   be  removed  extravascularly.    Clinically  manifest   with  jaundice   from   unconjugated  bilirubin.    Spectrin  defect   and  AD  dz;  splenomegaly  always   seen   over   a   period   of   time.     Gallbladder   (GB)   dz   is   common   b/c   there   is   a   lot   more   unconjugated  bilirubin  presented  to  the  liver  and  more  conjugation  is   occurring  and   more   bilirubin   is   in   the   bile   than  usual.   So,   whenever   you  supersaturate   anything   that  is  a  liquid,  you  run  the  risk   of  forming  a  stone;  if  you  supersaturate  urine  with   Ca,  you  run  the  risk  of  getting  a  Ca  stone;  if  you  supersaturate  bile  with  cholesterol,   you  will  get  a  cholesterol  stone;  if  you  supersaturate  with  bilirubin,  you  will  get  a  Ca-­‐ bilirubinate  stone.    Therefore,  pts   have  GB  dz  related  to   gallstone  dz  and  then  do   a   CBC   with   normocytic   anemia   and   a   corrected   ret   ct   that   is   elevated,   and   see   congenital  spherocytosis.    What’s   the  diagnostic   test?  Osmotic  fragility  –  they  put   these   RBC’s   wall   to   wall   in   different   tonicities   of   saline,   and   the   RBC’s   will   pop   (therefore  have  an  increased  osmotic  fragility).    

Rx:     splenectomy  (need  to  remove  organ  that   is   removing  them   –  they   will  still  be   spherocytes  and  will  not  be  able  to  form  a  biconcave  disk).  

(b)    Paroxysmal  Nocturnal  Hemoglobinuria  =  defect  in  decay  accelerating  factor.     So  when  we  sleep,  we  have  a  mild  resp  acidosis  b/c  we  breathe  slowly   (if  you  have   obstructive   sleep   apnea,   the   acidosis   is   worse).   When   you   have   acidosis   that   predisposes   the   complement   that’s   sitting   on   ALL   cells   circulating   in   peripheral   blood.     RBCs,   WBCs,   and  platelets   all   have   complement   sitting   on  it.     There   is   no   complement   destruction   of   these   cells   b/c   in   our   membranes   we   have   delay   accelerating  factor.    This  factor  causes  increased  degradation  of  the  complement  so  it   doesn’t  have  an  opp  to   drill  a  hole  in  our   membrane,  therefore  we  don’t  wake  up  in   the  morning  with  hemoglobinuria,  neutropenia  and  thrombocytopenia.    So,  if  you  are   missing   decay   accelerating  factor,   the   complement   will  be   activated  and  goes   from   C1-­‐9,   leading   to   intravascular   hemolysis.     Think   about   the   name   (paroxysmal   nocturnal  hemoglobinuria):  occurs  at   night,  and  when  you  wake  up  in  the  morning,   you  pee  out  hemoglobin.    So,  when  you  do  a  CBC,  not  only  have  a  severe  anemia,  but   also  a  neutropenia  and  a  thrombocytopenia:  pancytopenia).

2.    Abnormal  Hb:  Sickle  Cell  Trait/Dz

With   sickle   cell   trait,   there   is   NO  anemia   and   NO  sickled  cells   in   the   peripheral   blood.    You  can  have  sickled  cells  in  a  certain  part  of  your  body  –  in  the  renal  medulla   within  the   peritubular   capillaries  (decreased  O2   tension),   but   not   in  the  peripheral  

blood.    This  is  b/c  in  SCDz,  the  amount  of  sickled  Hb  in  the  RBC  determines  whether   it  sickles   or  not.    Magic  #  =  60%;  if  you  have  60%  or  more,  HbS  can  spontaneously   sickle.    Oxygen  tension  in  the  blood  also  determines  whether  a  cell  will  sickle  or  not.     At   lower   O2   tensions,  cells  are  more  likely  to  sickle.  This  is  an  auto   rec  dz,  meaning  

that   both   parents   must   have   abnormal   gene   on   their   c’some   (so   its   2   traits);   therefore,   25%   complete   normal,   50%   heterozygous   asymptomatic   carrier,   25%   complete  dz  (same  with  cystic  5ibrosis).

SC  Trait  vs.  SCDz:

(a)     In   sickle   cell   trait,   black   individual   with   normal   PE   and   normal   CBC,   but   microscopic   hematuria,  the  5irst   step  is  sickle  cell  screen  b/c   microscopic  hematuria   is   ALWAYS   abnormal  and  must   be   worked  up  but   in  blacks   =  1/8  people  have   the   trait.     So,   SC   trait   is   what   you   are   thinking   of;   not   renal   stones,   or   IgA   glomerulonephritis,  but  is  SC  trait  normally.

(b)    SCDz  –  2  things  are  happening:    Hemolytic  anemia  (usually  extravascular)  –  can   be  very  severe  and  commonly  requires  a  transfusion  and  Occlusion  of  small  BV’s  by   the   sickled   cells   (blockage   of   circulation)   –   lead   to   vasooclusive   crisis,   and   this   ischemia   leads   to   pain.    Therefore,   they   are   painful  crisis   (occur   anywhere  in   the   body  –  lungs,  liver,  spleen,  BM,  hands/feet  (bactulitis)).    Over  time,  it  leads  to  damage   of  organs  –  kidneys,  spleen  autoinfarcted  (autosplenectomy)  –  in  5irst  10  years  of  life,  

pt   will   have   splenomegaly   b/c   trapped   RBC’s,   and   eventually   autosplenectomy   around  age  19  (spleen  will  be  the  size  of  a  thumb).    After  2  years,  it  is  nonfunctional  –   so   even  though  you  have  a  big/swollen  spleen,  it  isn’t  working.    How  will  you  know   what  that  has  happened?  Howell  Jolly  body  (RBC  with  a  piece  of  nucleus  that   should   not   be   in  the  spleen  –  if  the  spleen  were   working,   a  5ixed  macrophage   would  have   taken  care  of  it).    This  occurs  at  about  2  yrs  of  age.    This  is  fortunate  b/c  this  is  about   the  age  where  you  can  get  pneumovax.    With  a  nonfunctional  spleen  what  infection  is   guaranteed?  Strep  pneumoniae  sepsis.

MCC  death  in  child  with  SCDz  =  strep  pneumoniae  sepsis.

They  try  to  cover  with  antibiotics  and  pneumovax  –  pneumovax  can  be  given  at  the   age  of  2  and  that’s  about  the  time  when  the  spleen  stops  working  (start  to  see  Howell   jolly  bodies).    Slide  with  Howell  jolly  body  and  slide  with  sickled  cells,  then  will  ask,   what’s   wrong   with   the   spleen?   It’s   dysfunctional;   Howell   jolly   would   have   been   removed  if  the  spleen  is  functional.    

When  do   they  get   their   5irst   sickle  cell  crisis?   When  little  kids   gets  painful  hands,   and   are   swollen  up   (called   bactulitis)   –   does   not   occur   at   birth,   b/c   HbF   inhibits   sickling   and   newborns   in   newborns,   70-­‐80%   of   their   RBC’s   are   HbF.     In   SCDz,   60-­‐70%  RBC’s  have  HbF,  while  the  rest  are  HbS!

At  this  stage,  there  is  enough  HbF   to  inhibit  the  sickling;  however,  as  the  RBC’s  are   broken  down  and  replaced,  the  HbF  decreases  and  HbS  increases,  and  by  6-­‐9  months   of   age,   there   is   a   high   enough   concentration   to   induce   sickling   and   their   5irst   vasooclusive  crisis,  producing  bactulitis.    So,  bactulitis  doesn’t  come  until  6-­‐9  months   b/c  HbF  inhibits  the  sickling.    

Bone  infarctions  occur  from  sickling  the  BM.    

Osteomyelitis  –  these  pts  are  susceptible  to  osteomyelitis  from   salmonella  due  to  a   dysfunctional  spleen.    Salmonella  is  destroyed  by  macrophages.    The  spleen  normally   5ilters   out   salmonella,  but   is  dysfunctional.     MCC  osteomyelitis   is   staph,  but  MCC  in   SCDz  pt  =  salmonella.    

What  drug   is   used  to   decrease   the  incidence  of   vasooclusive  crises?   Hydroxyurea.     How  does  it  work?  It  increases  HbF  synthesis.    

3.    DeUiciency  of  enzyme:    G6PD  deUiciency G6PD  def  is  X-­‐linked  recessive.    

Most  enzyme  def’s  are  auto  recessive  ie  PKU,  albinism,  homocystinuria).    What  are   the   two   X-­‐linked   recessive   enzyme   def’s?   G6PD   def   and   Lesch-­‐Nyhan   syndrome   (involves  purine  metabolism  with  mental  retardation,  self  mutilation,  increased  uric   acid,  def  of  HGPRT).  

Glucose   6  phosphate   has   several   functions:  (1)   to   make  glutathione,   (2)   to   make   ribose   5   carbon   sugars   for   making   DNA,   and   (3)   to   make   glycogen   from   G6P   (converted  to  G1P,  UDP-­‐glucose  and  glycogen).    

Key:  with  this   enzyme,   we  can  make  NADPH,   which  is   the  main  factor  for  making   anabolic  types  of  biochemical  rxn  (ie  steroid  synthesis).    NADPH  will  reduce  oxidized   glutathione  to  glutathione;  its  job  is  to   neutralize  peroxide  to  water.    Which  vitamin   catalyzes  this  rxn?  Ribo5lavin.    Which  enzyme  helps  glutathione  neutralize  peroxide?   Glutathione  peroxidase.    Which  trace  metal  is  involved?   Selenium.    Every  living  cell   makes   peroxide   as   an   end   product,   therefore   every   cell   must   a   way   to   handle   it.     Catalase  –  present  in  all  cells  except  RBC’s  and  it  can  neutralize  peroxide.    It  is  stored   in  peroxisomes.     Other   way   to   neutralize   peroxide  is   with  glutathione   (only   thing   available   to   RBC’s   b/c   they   don’t   have   catalase).     So,   if   you   are   de5icient   in   this   enzyme,  there  is  a  problem.    So,  peroxide  increases  to  the  point  of  hemolyzing  RBC’s   why  would  that  occur?  B/c  if  you  had  an  Infection,  or  if  you  took  an  oxidizing  drug  (ie   sulfa  drug,  nitryl  drug),  which  will  lead  to  a  lot  more  peroxide  lying  around.    Peroxide   will  not  be  able  to  be  neutralized  if  you  are  de5icient  in  catalase.    So,  what  will  happen   is  the  peroxide  will  affect  the  Hb.  The  peroxide  will  cause  the  Hb  to   clump  and  form   Heinz  bodies  (Hb  clumped  up  together).      Will  also   affect  the  RBC  membrane  b/c  it   damages   the   membrane   so   much   that   the   primary   mechanism   of   destruction   is   intravascular.     Little   element   is   extravascular,   but   mostly   intravascular.     It   is   precipitated  by  infections  and/or   drugs.     2   MC  drugs:  1)  primaquine–  missionary   got  malaria,  received  a  drug,  and  2-­‐3  days  later  the  got   hemoglobinuria,  chills,  and  a   hemolytic   anemia   (this   is   primaquine  induced  hemolysis).     2)   Dapsone   is   used  in   treating  leprosy;  every  person  with  leprosy  is  given  a  screen  for  G6PD  def  b/c  of  the   high  incidence  of   producing   hemolysis.    See  this  dz  in  the  same  population  as  Beta   thal  –   blacks,  Greeks,  Italians.    Slide:  smear  with  actively   hemolyzing  blood  cells  –   Heinz  bodies  –  when  it  goes  into  the  cords  of  bilroth,  the  macrophage  will  take  a  big   bite  out  of  it  and  sometimes,  is  a  small  bite  out  of  the  membrane,  and  the  cell  goes  to   the   peripheral   circulation  and   is   called   a   “bite”   cell   (RBC  with   little   membrane).     Need  to  do  special  stains  to  ID  Heinz  bodies.    In  Greeks  or  Italians  with  severe  forms   of  G6PD  def,  they  can  eat  fava  beans  which  can  precipitate  an  episode  (aka  favism).

Dx   –  when  you  have  an  acute  hemolytic   episode,   the  last   thing  you  want   to  get   a   diagnosis  is  to  get  an  enzyme  assay.    Why?    B/c  the  only  cells  that  are  hemolyzed  are   the   ones   missing   the  enzymes.    The  ones   that   have   the  enzyme   are   still  gonna   be   there,   so   you   have   a   normal   assay.     So,   NEVER   use   enzyme   assays   for   active   hemolysis.    Need  to  special  stain  to  ID  the  Heinz  body.  When  the  hemolytic  episode  is   over   that’s   when   the   dx  is   con5irmed,  this   is   done   with   a  G6PD   assay.     Will   get  a   question  on  G6PD  deUiciency,  either  dapsone  related  or  primaquine  related.

X.    Autoimmune  hemolytic  anemias

MC  autoimmune  hemolytic  anemia  =  warm;  MCC  of  it  =  Lupus

When  you   have   autoimmune   dz  in  your   family,   you  have   certain  HLA   types   that   predispose   you  to   that   autoimmune  dz.    Therefore,   you  should  not   be   surprised   if   you   have   one   autoimmune   dz   you’re   likely   to   have   another.     So,   pts   with   lupus   commonly   also   have   autoimmune   hemolytic   anemia,   autoimmune   thrombocytopenia,  autoimmune  neutropenia,  and  autoimmune  lymphopenia.  

For   example:   the   MCC   of   hypothyroidism   =   hashimoto’s   thyroiditis;   these   pts   commonly  have  other  autoimmune  dz’s  –  ie  pernicious  anemia,  vitiligo,  autoimmune   destruction  of  melanocytes).     So,  if  you  have  one  autoimmune  dz,   you  are  likely   to   have  others  (ie  if  you  have  a  hemolytic  prob,  it  is  prob  autoimmune  related).    

This   is   b/c   of   the   HLA   relationship.     Therefore,   if   you   have   a  family   that   has   an   autoimmune  dz,  what   would  be  the  single  best   screening  test  to  use?   HLA  (ie  if  they   have   the   HLA   type   speci5ic   for   lupus   –   there   are   speci5ic   HLA’s   for   diff   dz’s).     Therefore,  HLA  is  the  best  way  to  see  if  pt  is  predisposed  to  something.

MCC  autoimmune   anemia   =  Lupus;  it   has  IgG  and  C3b   on  the  surface  of  the  RBC,   so  it  will  be  removed  by  the  macrophage.    This  is  an  extravascular  hemolytic  anemia.     How  do   we   know  that   there  are  IgG   or   C3b   Ab’s   on  the  surface?     Direct   Coomb’s   test:   detect   DIRECTLY   the   presence   of   IgG   and/or   C3b   on   the   surface   of   RBC’s.     Indirect  coombs  is  what  the  women  get,  when  they  are  pregnant  and  they  do  an  Ab   screen  on  you  (looking  for   any  kind  of  Ab);  so,   when  you  look   for   Ab   in  the  serum   (NOT  on  RBC,  on  SERUM),   this   is   an  indirect   Coombs.    Therefore,   another  name  for   the  indirect   Coombs   =  Ab  screen;  with  direct   coombs,  we  are  detecting  IgG  and/or   C3b   on   the   SURFACE   of   RBC’s.     you   cannot   do   direct   coomb’s   on   platelets   or   neutrophils,  but  only  RBC’s.

So,   the   test   of   choice   if   you   suspect   an   autoimmune   hemolytic   anemia   is   Coomb’s  test.