Hyposplenism

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Hyposplenism

• Presented by Melissa Smith

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Overview

• Definition of Hyposplenism
• Medical History
• The function of the spleen
• Congenital asplenia vs. splenectomy
• Immunological consequences of Hyposplenism
• Diagnosis and complications

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What is Hyposplenism?

• Hyposplenism is the lack of a spleen or its
  function
• The rare genetic disorder- Congenital Asplenia
• The surgical removal of the spleen- splenectomy
• Results in severe immunological consequences.

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History

• Immunological importance of the spleen
• Morris and Bullock-1919
• First post-splenectomy infection
• ODonnell-1929
• Effects of Hyposplenism
• King and Shumacker-1952

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The Spleen

• Largest lymphoid tissue of the body
• Serves two main functions
• Filters blood to remove damaged/old RBC- red pulp
• Serves as secondary lymphoid tissue by removing
  infectious agents and using them to activate
  lymphocytes- white pulp
• A significant reservoir for T lymphocytes
• Plays an active role in the production of IgM
  antibodies and complement
• Has significant role in the functional maturation
  of antibodies

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Anatomy of Spleen
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Spleen Structure

• The white pulp is circular in
• structure and is made up mainly
• of lymphocytes. It functions in a
• manner similar to the nodules of the
• lymph node.
• The red pulp surrounds the white
• pulp and contains mainly red blood
• cells and macrophages. The main
• function of the red pulp is to
• phagocytize old red blood cells.

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White Pulp
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Red Pulp
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Congenital Asplenia

• Autosomal recessive genetic disorder
• Believed to be caused by absence of the Hox 11
  gene in the embryo
• Causes decreased adaptive immune response
• Associated with structural abnormalities in other
  organs of the body- cause death in infancy

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Splenectomy

• Removal of spleen tissue (partial or complete)
• Usually needed because of trauma
• Residual splenic function in ¼ to ? of patients
• IgM levels decreases, IgG levels remain constant
  or increase, IgA and IgE levels increase

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Immunological Consequences

• Causes slower and incomplete adaptive immune
  response against bacteria
• Low levels of tuftsin, which stimulates
  phagocytosis by neutrophils, macrophages, and
  monocytes
• Decreased neutrophil and macrophage activity
• Increased NK cell activity
• Limited capacity of circulating B-cells to
  differentiate into antibody-secreting cells
• Decreased level of T-cells

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Diagnosis

• Determined by anatomic presence or absence of the
  organ, its size, and any lesions.
• Function can be assessed by
• Radiologic Techniques
• X-ray, ultrasound, tomography, MRI,
  radionucleotide scanning
• Morphologically
• Peripheral blood smear- presence of Howell-Jolly
  bodies

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Howell Jolly bodies

• Howell-Jolly
• bodies are round, purple
  staining nuclear fragments of
  DNA in the red blood cell

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Complications

• Lifelong risk for Overwhelming Postsplenectomy
  infection (OPSI)
• Caused by Streptococcus pneumoniae and gram
  negative bacteria
• Initial Symptoms fever, chills, muscle aches,
  headache, vomiting, diarrhea, and abdominal pain
• Progressive symptoms bacteremic septic shock,
  extremity gangrene, convulsions, and coma
• Mortality rate of 50-80
• from onset of initial symptoms, 68 of those
  deaths occur within 24 hours and 80 occur within
  48 hours
• Prevention routine vaccinations and prophylactic
  antibiotics

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Summary

• Hyposplenism is the lack of a spleen or its
  function
• Can be either genetic or surgically induced
• It has detrimental effects on the immune system
  by decreasing the bodys ability to fight
  bacterial infections and reducing the adaptive
  immune response

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Resources

• Asplenia. Mudra Kumar, MD, MBBS, MRCP. EMedicine.
  19 September 2005. http//www.emedicine.com/ped
  /topic150.htm
• Asplenia Defined. Families.com. 19 September
  2005. http//encyclopedias.families.com/asplenia-1
  12- 115-gecd
• Bowdler, Anthony J.. The complete spleen
  structure, function, and clinical disorders . 2nd
  ed. Totowa, N.J. Humana Press, 2002.
• Brigden, M. L. Detection, education and
  management of the asplenic or hyposplenic patient
  a patient information handout is provided.
  American Family Physician v. 63 no. 3 (February 1
  2001) p. 499-508
• Feder, H. M. J., et. al., Assessment of splenic
  function in familial asplenia. The New England
  Journal of Medicine v. 341 no. 3 (July 15 1999)
  p. 210-12
• Gilbert-Barness, Enid., Diane E. Debich-Spicer.
  Handbook of pediatric autopsy pathology. Totowa,
  N.J. Humana Press, c2005.
• Kanzler, B., et. al., Hox11 acts cell
  autonomously in spleen development and its
  absence results in altered cell fate of
  mesenchymal spleen precursors. Developmental
  Biology v. 234 no. 1 (June 1 2001) p. 231-43
• Neiman, Richard S., Attilo Orazi. Disorders of
  the spleen . 2nd ed. Philadelphia W.B.
  Saunders, c1999.
• Romanovsky, A. A., et. al., The spleen another
  mystery about its function Editorial. American
  Journal of Physiology v. 284 no. 6 (June 2003
  pt2) p. R1378-9
• Sunder-Plassmann, G., et. al., Functional
  asplenia and vasculitis associated with
  antineutrophil cytoplasmic antibodies. The New
  England Journal of Medicine v. 327 (August 6
  1992) p. 437-8
• Tice, A. Hope for patients with asplenia or
  hyposplenism editorial. American Family
  Physician v. 63 no. 3 (February 1 2001) p.
  439-40