Thursday, December 23, 2010

Clinical Case: Trisomy 21 Complications

Clinical Vignette: A  42-year-old  woman  is pregnant  and  undergoes amniocentesis.  The  results of  the  amniocentesis are  consistent  with  trisomy 21,  but  the  woman  wishes  to  carry  the pregnancy  to  term.  After birth,  this  child  will  be  at  increased  risk for  the  development  of  which  of  the  following neoplasms? 

       A. Acute lymphoblastic leukemia 
       B. Basal cell carcinoma 
       C. Colon cancer 
       D. Glioblastoma multiforme 
       E. Hodgkin's disease 


The  correct answer  is A. This clinical vignette mentions another common USMLE question. In addition  to the  well-known mental  retardation associated  with Down's syndrome  (trisomy 21),  affected individuals  have  an increased  incidence  of a  variety of  medical problems.  Acute  myeloblastic  leukemia is  seen  in  newborns  and  acute lymphoblastic  leukemia  is seen  in older  children.  Epilepsy, which  can be  very  difficult to  manage,  affects up  to 10%  of children  with Down's.  On  occasion, the  malformed  head  and neck  region  can undergo  atlantoaxial dislocation,   causing  a   sudden  or  progressive  quadriparesis.  Congenital  malformations  of  the cardiac  system are  common (40%  of cases),  and  include (in  decreasing order  of frequency)  atrial and   ventricular  septal   defects,  tetralogy   of  Fallot,   and  patent   ductus  arteriosus.   The 
development  of  the  hypopharynx  is  often  poor,  predisposing  to  both  aspiration  pneumonia  and obstruction  by  enlarged  adenoids.  Other  malformations that  occur  with  lower  frequency  include duodenal  atresia and  imperforate  anus.  Acquired autoimmune  hypothyroidism  is  frequent. Boys  are 
infertile;  girls  are  subfertile  but  can  get pregnant.  Alzheimer-like  changes  develop  in  mid-adulthood.  Visual problems  related  to strabismus,  nystagmus,  or  myopia are  common.  None of  the other neoplasms occur with increased frequency in individuals with trisomy 21.