RT Book, Section
A1 Bonilla-Guerrero, Ruben
A1 Kloke, Karen M.
A1 Salazar, Denise
A1 Sharma, Rajesh
A2 Sarafoglou, Kyriakie
A2 Hoffmann, Georg F.
A2 Roth, Karl S.
SR Print(0)
ID 1140318774
T1 The Porphyrias
T2 Pediatric Endocrinology and Inborn Errors of Metabolism, 2e
YR 2017
FD 2017
PB McGraw-Hill Education
PP New York, NY
SN 9780071773140
LK accesspediatrics.mhmedical.com/content.aspx?aid=1140318774
RD 2024/04/19
AB The  porphyrias  are  a  group  of  inborn  errors  of  metabolism  resulting  from  enzymatic  defects  in  heme  biosynthesis.  The  majority  of  the  porphyrias  are  inherited  in  an  autosomal  dominant  manner,  with  most  subjects  retaining  approximately  50%  of  normal  enzyme  activity.  In  most  cases,  this  is  sufficient  to  maintain  heme  biosynthesis.  However,  the  pathway  can  be  upregulated  by  precipitating  factors  that  increase  the  demand  for  heme.  Depending  on  which  enzyme  is  defective,  different  heme  pathway  intermediates  are  overproduced,  accumulate,  and  are  excreted  in  urine,  feces,  or  both.  The  excess  amount  of  these  intermediates  gives  rise  to  clinical  manifestations  which  may  include  neurological  and  psychological  symptoms  and/or  cutaneous  photosensitivity.  Heme  pathway  enzymes  can  also  be  disrupted  in  other  disorders,  by  heavy  metal  toxicity,  or  by  various  chemicals,  with  the  resulting  clinical  picture  resembling  a  porphyria.