Protruding Sternum

Primary Reasons for a Protruding Sternum

Millions of people have a protruding sternum, which involves the breastbone protruding or pushing against the skin.  Depending on the cause, the appearance may be noticeable or it could just be a slight bump.  There are actually several different reasons for this, a few of the more common listed in this article.  Sometimes, the condition is nothing more than an annoyance while other times it could be the sign of something very serious, even life-threatening occurring.  Therefore, anyone who notices the sternum starting to stick out should be checked by a doctor right away.



Marfan syndrome

Marfan syndrome is actually a disorder of the connective tissue that involves a number of structures within the body to include the lungs, heart, eyes, blood vessels, and skeletal system.  Marfan syndrome occurs when a person has a defect of the 15q21 chromosome.  In a normal person, this chromosome produces a substance called fibrillin that along with other things produces the body’s connective tissue.

The most common symptoms associated with Marfan syndrome include tallness, thinness, and abnormalities of the skeletal system to include a protruding sternum among other things.  Again, because a sternum sticking out could be something serious such as this, it is essential to seek medical assistance.

Pectus Carinatum

Another possible reason for a protruding sternum is this disorder, also referred to as “Pigeon Chest.”  In addition to the sternum protruding, the individual would also experience protruding ribs.  When in reverse, Pectus excavatum manifests as a sunken chest.  The cause of Pectus Carinatum is an overgrowth of cartilage, which reaches the point of pushing the sternum outward.  The cause of this disorder could be one of three things:

  1. Growth Spurts – The most common of the three causes is seen primarily in boys between 11 and 14 years of age.  When a significant growth spurt is experienced, the protrusion develops.

  2. Birth – In some cases, a person is born with this problem.  Typically, it would be noticed in a newborn baby as a rounded chest.  However, as the child ages, the protrusion would be more evident by age three.

  3. Surgery – Although relatively rare, a protruding sternum associated with this condition could be the result of surgery.  In this case, instead of the sternum healing flat, it actually heals with bowed.


This condition is also called “Tietze’s syndrome”, which involves cartilage of the rib cage, specifically where the ribs are joined to the breastbone.  As the cartilage becomes inflamed, the person would experience pain, sometimes so severe it mimics a heart attack.  In addition, it is common for the pain to be felt in different areas of the body although most people feel it in the chest region.  Along with pain, sometimes a protruding sternum is seen with Costochondritis.

Osteogenesis Imperfecta

This genetic bone disorder is known by several names to include “OI”, “Lobstein syndrome”, and “Brittle Bone Disease”, which actually has eight different types.  Regardless, person is born with defective connective tissue.  Additionally, the individual may or may not be born with the ability to produce it.

If the body cannot produce needed connective tissue, the primary reason is a deficiency of Type I collagen, which means that glycine, a type of amino acid is produced instead of bulkier amino acids within the collagen triple helix structure.  Without connective tissue, a low amount of connective tissue, or the substation of amino acids, molecular interaction is compromised.  For any of these scenarios, the body often responds by modifying collagen structure.


What happens is that if the wrong collagen is not destroyed, fibrils associated with collagen and hydroxyapatite crystals begin to form, altering the bone structure.  The result is the bones becoming brittle and often, a protruding sternum.

Several other syndromes and genetic disorders can cause the problem with a protruding sternum, some that include Trisomy 18, Trisomy 21, Multiple Lentigines syndrome, Sly syndrome, Nooran syndrome, Morguio syndrome, and Homocystinuria.