Splenomegaly and Infectious Mononucleosis

In light of recent tragedy, with heavy heart and great respect for grieving family and friends of the young athlete that recently passed away from spleen rupture, I would like to review the  most common medical condition that may cause splenomegaly (enlarged spleen), where premature resumption of sports can be life-threatening.


In order to understand why spleen gets enlarged, it would be beneficial to review many different functions of spleen. Imagine spleen as yin and yang.  Yang, the white part, represent “white pulp”of the spleen.   It is made of lymphatic tissue.  Spleen is one of many immunological centers in our body where antibodies get formed in response to various antigens (e.g.viruses, bacteria,yeast, etc).  Yin, the dark part, represents “red pulp” of the spleen.  As the name implies, it is a very vascular part of the spleen.  Its function is to destroy any cells that are abnormal.  Spleen also acts as a reservoir for platelets.  As a result of these many functional components within the spleen, the etiology of splenomegaly may relate to an increase in a normal splenic process (e.g., hemolysis) or may be due to infiltrative, infectious, or vascular disorders.

In this post, I am only going to be concentrating on a tip of the iceberg – Infectious Mononucleosis (also known as Glandular fever, Kissing disease, Mono or Mononucleosis). For the most of us, when we hear our children complaining of sore throat, we immediately tend to think of strep pharyngitis. The association between the two and consequences of untreated Group A strep pharyngitis seem to be ingrained in our minds.  Parents call in desperation at all hours of the day and request to be seen that same day to “rule-out “strep.  You can see relieve on their faces when you inform them that rapid strep is negative.  Once they hear good news, all the worries they had dissolve.mononucleosis

One of many other causes of pharyngitis is due to Infectious Mononucleosis. Mono is characterized by a triad of fever, sore throat, and enlarged lymph nodes.  Some kids may also feel fatigued, have tonsillar exudates (pus on the tonsils), where others will have rash.  There are many clinical variants.  At times it may be difficult to make diagnosis just based on the history and physical exam alone.

When suspicion for Infectious Mononucleosis is high, some physicians obtain supportive evidence in a form of laboratory test. Increasing number of atypical lymphocytes along with positive heterophile antibody test (Monospot) are highly suggestive of infectious mononucleosis. Infectious Mononucleosis is mostly caused by Epstein-Barr virus (EBV) or cytomegalovirus (CMV). Since it is a viral infection, the mainstay of treatment for individuals with infectious mononucleosis is supportive care.

So why do we go to such extend to identify this illness? Splenomegaly.  Splenomegaly is seen in half of the patients with Infectious Mononucleosis and usually begins to recede by the third week of the illness.

Splenic rupture is a rare but potentially life-threatening complication of Infectious Mononucleous. It’s estimated to occur in one to two cases per thousand, with almost all reports have been in males. It mostly occurs between the fourth and twenty-first day of symptomatic illness. All athletes should refrain from sport activities during early illness. Recommendations to resume sports are somewhat arbitrary given the lack of prospective data. Most physicians adopt a more universal four week time frame regardless of activity level.

Splenic palpation or percussion is generally unreliable in athletes with firm abdominal musculature. The safest option may be obtaining an ultrasound examination to document resolution of splenomegaly. However, the use of imaging studies before a return to sports remains a debated issue due to a lack of clinical outcomes data and the cost of ultrasound.


  1. Haines JD Jr. When to resume sports after infectious mononucleosis. How soon is safe? Postgrad Med 1987; 81:331.
  2. Auwaerter PG. Infectious mononucleosis: return to play. Clin Sports Med 2004; 23:485.
  3. Infectious Mononucleosis, Carter RL, Penman HG (Eds), Blackwell Scientific Publication, Oxford and Edinburgh 1969. p.47-62

Dr. Alla

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