TY  - CHAP
M1  - Book, Section
TI  - Glycogen Storage Disorders
A1  - Cristian, Ingrid
A1  - Wasserstein, Melissa
A2  - Murray, Michael F.
A2  - Babyatsky, Mark W.
A2  - Giovanni, Monica A.
A2  - Alkuraya, Fowzan S.
A2  - Stewart, Douglas R.
PY  - 2014
T2  - Clinical Genomics: Practical Applications in Adult Patient Care
AB  - Disease  summary:Glycogen  storage  diseases  (GSDs)  are  a  group  of  inherited  disorders  of  glycogen  degradation  or  synthesis.  Because  glycogen  is  stored  mainly  in  the  liver,  skeletal  muscle,  and  heart  muscle,  the  clinical  spectrum  of  the  GSDs  is  defined  by  involvement  of  these  organs.Currently,  there  are  10  well-defined  types  initially  enumerated  in  order  by  which  the  enzymatic  defect  was  identified.  As  the  genetics  of  the  glycogen  pathway  became  clearer,  different  types  of  GSD  have  been  grouped  together,  as  is  the  case  with  type  VIII  and  X  which  are  now  considered  part  of  type  VI.Types  0,  I,  III,  VI,  IX,  and  XI  mainly  involve  the  liver,  causing  hypoglycemia  and  hepatomegaly.  Type  IV  disease  also  involves  the  liver,  but  typically  causes  cirrhosis  and  liver  failure  in  the  absence  of  significant  hypoglycemia.  Types  II,  V,  and  VII  mostly  affect  the  muscle.  Patients  with  type  II  classically  have  cardiomyopathy  and  skeletal  muscle  weakness,  whereas  muscle  pain,  fatigue,  and  exercise  intolerance  characterize  the  latter  two  types.Hereditary  basis:Most  GSDs  follow  an  autosomal  recessive  inheritance.  Some  patients  with  GSD  V  who  were  thought  to  be  manifesting  heterozygotes  (only  one  mutation  found  in  the  PYGM  gene)  recently  were  found  to  carry  a  putative  mutant  allele  when  studies  were  performed  on  the  cDNA  in  skeletal  muscle.GSD  type  IX  is  subdivided  depending  on  the  affected  subunit  of  the  phosphorylase  kinase.  When  the  α  subunit  is  affected,  this  disorder  follows  an  X-linked  inheritance,  whereas  β  and  γ  subunit  deficiency  follow  an  autosomal  recessive  inheritance  pattern.Differential  diagnosis:The  initial  approach  to  diagnosing  a  GSD  is  based  on  the  primary  presenting  feature.  For  example,  patients  with  hypoglycemia  and  hepatomegaly  should  be  evaluated  for  the  hepatic  GSDs  (I,  III,  VI,  IX)  whereas  patients  with  myopathy  and  muscular  weakness  in  the  absence  of  hypoglycemia  should  be  evaluated  for  the  muscular  GSDs  (II,  V,  VII).The  differential  diagnosis  of  hypoglycemia  is  extensive  and  includes  excessive  insulin  production  or  poorly  controlled  diabetes,  disorders  of  cortisol  production,  and  liver  disease.  The  differential  diagnosis  of  hypoglycemia  with  hepatomegaly  is  more  limited,  and  includes  mitochondrial  hepatopathies,  congenital  disorders  of  glycosylation,  fructose  1,6  bisphosphatase  deficiency,  Beckwith-Wiedemann  syndrome,  and  fatty  acid  oxidation  defects.The  differential  diagnosis  of  myopathy  and  hypotonia  includes  spinal  muscular  atrophy,  mitochondrial  or  respiratory  chain  disorders,  limb-girdle  muscular  dystrophy,  Duchenne-Becker  muscular  dystrophy,  hypothyroidism,  and  fatty  acid  oxidation  defects,  such  as  very  long  chain  acyl  coenzyme  A  dehydrogenase  (VLCAD).  
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/19
UR  - accessmedicine.mhmedical.com/content.aspx?aid=1102703373
ER  -