About congenital anomalies

 Definition of Congenital anomalies: 

Abnormalities of body structure that originate before birth.

Etiology:

  • Genetic:
  1. chromosome abnormality :

    6% in incidence & autosomal abnormalities and more severe than sex-chromosome.
    prenatal or postnatal retardation of linear growth, brain growth, mental retardation, and multiple anomalies of early embryogenesis.

  2. Single gene defect:
     7.5% 
    Isolated: in one organ or system e.g hydrocephalus, microphthalmia, polydactyly.
    Multiple: multiple organs or systems don't have an embryological relationship.
                   e.g. Meckel syndrome: Autosomal recessive (encephalophy& polydactyly and polycystic 
                          kidney.

       3. multifactorial: 
            majority of cases.
            polygenic inheritance of 2 or more genes includes interaction with the environment.
            Isolated malformations e.g. Cardiac (ASD & PDA) 
                                                       CNS (spina bifida )
                                                       Cleft lip/palate.
                                                        recurrence rate increases so need family study.

  • Environmental (Teratogens):
             recurrence risk depends on exposure to teratogenic factors e.g. drugs & infections & diabetic mother.

  • Unknown causes:
             50% of the reasons.
             very low to recurrent for siblings.
             e.g. Anal atresia & Isolated diaphragmatic hernia.

*Mechanisms:

         #malformation:
           Interrupted development.
           Intrinsic abnormal developmental process.
           e.g. cleft lip/ palate.

       #Deformation:
         Normal in structure & abnormal in position or shape due to mechanical forces e.g. (oligo hydrogenous           & neuromuscular disease & breach  or crowding  )
         good prognosis.
         example: craniofacial compression & dislocation of the hip.

      #Diruption:
        Extrinsic interference with normal development.
        e.g. * Amniotic bands which may lead to limb amputation. 
               * vascular disruption (atresia in early time & necrosis in the late time of pregnancy) 

     #Dysplasia:
        Mutant genes affect one general tissue type. e.g. Ectodermal Dysplasia & Osteogenesis Imperfecta.

 *Types:

 Major: affect body function or life e.g. VSD 
 Minor: cosmetic e.g. pre-auricular tags.

Isolated: 2/3 of all major types. 
              multifactorial inheritance.
              recurrence risk occurs.
              e.g. CHD & Clift lip.
Multiple: one or two major with several minor anomalies.
               Associations: non-random combinations.
                                      very low recurrence.
                                       e.g. VATER syndrome.
               Sequences: cascading process e.g. Potter oligohydramnios 
               Syndromes: things that runs together 2 or 3 key features e.g. Down syndrome.

 

Clift lip/palate


May you also like: Examples of congenital anomalies



AaseJM.Diagnostic Dysmorphology.New York, NY:Plenum;1990.
Bishara N, Clericuzio C. Common dysmorphic syndromes in the NICU. NeoReviews.2008;9:e29-e38.




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