RT Book, Section
A1 Amato, Anthony A.
A1 Russell, James A.
SR Print(0)
ID 1115657296
T1 Spinal Muscular Atrophies
T2 Neuromuscular Disorders, 2e
YR 2015
FD 2015
PB McGraw-Hill Education
PP New York, NY
SN 9780071752503
LK neurology.mhmedical.com/content.aspx?aid=1115657296
RD 2024/04/23
AB The  spinal  muscular  atrophies  (SMAs)  have  been  historically  conceptualized  as  hereditary  disorders  preferentially  affecting  anterior  horn  cells  and  selected  motor  cranial  nerve  nuclei.1  As  in  all  disorders  caused  or  influenced  by  genetics,  molecular  biology  has  served  to  confound  as  much  as  clarify  the  nosology.  We  have  become  very  aware  that  the  historical  boundaries  of  hereditary  neuromuscular  disease  are  inaccurate.  Part  of  this  confusion  arises  from  phenotypic  overlap.  For  example,  although  lower  motor  neuron  (LMN)  morbidity  dominates  most  SMA  phenotypes,  upper  motor  neuron  (UMN)  features  may  occur  in  some  forms  of  distal  SMA.  Conversely,  hereditary  spastic  paraplegia  is  a  predominantly  UMN  disorder  but  may  have  notable  LMN  features  in  some  genotypes.  Even  more  damaging  to  the  historical  nosology  of  hereditary  neuromuscular  disease  is  the  discovery  that  mutations  of  a  single  gene  may  produce  variable  phenotypes  that  have  been  historically  represented  as  two  or  more  diseases  (Table  8-1).