Pectus Excavatum Causes: What Science Knows (and Doesn't)

You’ve noticed the dip, in your own chest or your child’s, and the first question is why. The honest answer is that nobody knows the single cause. The problem seems to sit in the costal cartilage, the flexible strips that join the ribs to the breastbone. It often runs in families. A minority of cases come with a genetic syndrome or after specific events such as heart surgery. And nothing you did caused it.

Plenty of pages state some causes as settled when they aren’t. So below, every suggested cause gets a grade for its evidence, and every number comes with the people it was measured in. New to the condition? Start with what pectus excavatum is.

I was diagnosed with pectus excavatum at 15 and corrected it without surgery over about three years. The change was visible and measurable, but not complete. I’m not a doctor, so everything clinical here comes from published studies and hospital sources.

Every cause at a glance

The grades are my own reading of the research, not an official scale.

• Well documented: several studies agree.
• Mixed: studies point both ways.
• Early or small: single families, small series or animal work.
• Abandoned or unrelated: tested and dropped, or not found in people with pectus.
• No study found: I couldn’t find research that tested it.

Suggested cause	Grade	Verdict
Family history	Well documented	Roughly 4 to 5 in 10 patients have an affected relative
A specific gene	Early or small	About 14 candidates, mostly from single families and not repeated
Cartilage growing too long	Mixed	The most popular theory; scan studies disagree
Weak cartilage, rib overgrowth, breastbone growth	Early or small	Plausible, not shown
Diaphragm pulling the breastbone in	Abandoned or unrelated	Tested and dropped
Rickets or low vitamin D	Abandoned or unrelated	Older studies found no signs of it in people with pectus
Growth spurt	Well documented	Explains when it worsens, not why
Marfan, Noonan, Loeys-Dietz	Well documented	Common in these syndromes; most people with pectus don’t have one
Turner syndrome	Early or small	A broad chest is typical; true pectus in a few
Ehlers-Danlos syndrome	Early or small	Reported more often; most people with pectus don’t have EDS
Klinefelter syndrome	No study found	One case report; no measured link
Open-heart surgery	Early or small	Can appear or worsen afterwards
Diaphragmatic hernia at birth	Mixed	More pectus in some series, not in others
Blocked airway or SMA type 1 in infancy	Early or small	Small studies and case reports
Premature birth	No study found	Only a different rib pattern has been studied
Posture	No study found	Common alongside pectus; not shown as a cause
Weight, exercise, sleep, smoking	No study found	Not tested, as far as I could find

It runs in families, but the numbers are easy to misread

Family history is the best-supported finding there is. About 1 to 8 people per 1,000 have pectus excavatum, and it’s more common in boys, according to Cleveland Clinic. Cleveland adds that 40% to 53% of people with it have a family member with the same condition, without saying who was counted.

Studies that name their patients land in the same range. A 2022 Hamburg study surveyed patients with isolated pectus excavatum, meaning no known syndrome: 54% of the 78 with family data had an affected relative. In 206 patients operated on in Istanbul and followed up by phone, 47% reported a family history. That study was co-authored by Prof. Yüksel, the site’s medical reviewer.

How it’s passed down is less clear. Dominant means one copy of a gene change from one parent is enough; recessive means it takes a copy from each parent; X-linked means the gene sits on the X chromosome and tends to show up more in boys. A 2006 study of 34 US families found 14 that looked dominant, 4 recessive, 6 X-linked and 10 more complex, and concluded most are probably multifactorial: several genes plus other influences. A 2012 analysis of 48 family trees from the same Norfolk, Virginia, centre pointed mainly to recessive inheritance instead. The studies disagree.

They do agree on the boy bias. In the Istanbul group 85% were male, and so were five in six of 1,046 Danish surgical patients.

Will my children get it?

This is the part that’s easy to get backwards. “About half of patients have an affected relative” does not mean “a child of a parent with pectus has a 40-50% chance”. The first number looks back at relatives of people who already have it. It doesn’t count how many children of affected parents develop it. An earlier version of this page made that mistake.

I couldn’t find a study that gives a child’s risk. A 2014 clinical genetics review from Amsterdam says the risk for isolated pectus with no family history is unknown but thought to be low.

Is pectus excavatum genetic? What gene studies found

Genetics is part of the story, but no single gene has been found. The most recent summary I found, a 2026 UK systematic review, covers studies up to November 2025.

It found about 14 candidate genes or gene regions. Most were rare variants from a single family or case report, and most haven’t been repeated. Every study it included was done in European or East Asian people. And nobody has yet run a GWAS of isolated pectus excavatum: a scan comparing the genes of thousands of people with and without the condition.

The cartilage theory, and why it’s contested

The most common explanation is that the costal cartilage grows too long and buckles the breastbone inward. The Nuss procedure was designed around it, and a 2024 Dutch review still calls overgrowth or disturbed cartilage growth the leading hypothesis, while noting it’s controversial.

When researchers measured the cartilage on scans, results split:

• Against: Japanese CT studies found the cartilage on the deeper side shorter or no different, and the cartilage-to-rib ratio no larger than in people without pectus. A Florida study of 16 patients and 16 matched controls found cartilage was shorter relative to bone. And rats given a hormone that made their cartilage overgrow didn’t develop pectus, a 2022 systematic review notes.
• For a length problem: a Korean study of 19 adults found longer ribs, not longer cartilage. A 2020 Japanese study found the combined rib-and-cartilage length was longer than normal.

So the cartilage is probably involved, but “it grows too much” is a disputed theory, not a fact. The 2022 review lists other early ideas: weaker cartilage, ribs that grow too long, and disturbed growth of the breastbone itself. All plausible, none shown.

Theories that have been dropped

The oldest idea was that the diaphragm pulls the lower breastbone inward. It was abandoned: the deepest point of the dip usually sits above where the diaphragm attaches, and an operation designed to cut that pull didn’t correct the chest.

Rickets also gets listed, including by MedlinePlus. But older studies found no signs of rickets in people with pectus excavatum, and the 2022 review lists vitamin D as unrelated.

Why it often appears in the growth spurt

The growth spurt is when pectus excavatum tends to show up or deepen. Surgeons at a large Norfolk, Virginia, centre write that only 22% of cases are noticed in the first decade of life. At puberty a mild dip can become severe within 6 to 12 months, in their experience.

Researchers think fast skeletal growth may expose a mismatch between the ribs, cartilage and breastbone, but that hasn’t been demonstrated. The full timeline by age, including the adults whose dip keeps deepening, is in does pectus excavatum get worse with age.

Syndromes linked to pectus excavatum

Some genetic syndromes include a sunken chest, but most people with pectus don’t have a syndrome. Both are true because the numbers run in two directions: “how many people with Marfan have a pectus deformity” and “how many people with pectus have Marfan” have very different answers.

Condition	Pectus in people with the condition	The condition in people with pectus
Marfan syndrome	A pectus deformity, sunken or pigeon, in up to about 70% (UK review)	0.4% of 1,046 surgical patients (Denmark); 2.8% of 1,215 (US); 5.3% of 241 referred children (New York)
Loeys-Dietz syndrome	35 of 65 (54%), one US hospital	No figure found
Noonan syndrome	54% of 107 gene-confirmed patients (South India)	2 of 18 children under 11 at one Dutch clinic
Turner syndrome	Mild pectus in 3 of 15 (US, 1993)	No figure found
Ehlers-Danlos syndrome	3.7% self-reported (hypermobile EDS survey); 6 of 20 in one small series	2 of 1,046 surgical patients (Denmark)
Klinefelter syndrome	No study found	No study found

Marfan syndrome

Marfan is a connective tissue condition caused by changes in the FBN1 gene. It affects about 1 in 5,000 people, and at least a quarter of cases come from a new gene change rather than a parent, according to MedlinePlus Genetics. A UK review puts pectus deformity at up to about 70% of people with Marfan. That figure mixes sunken and pigeon chest, so it isn’t a pectus excavatum rate. In the revised Ghent criteria doctors use to score Marfan, pigeon chest even earns 2 points and sunken chest 1.

The other direction depends on who’s screened. Marfan was found in 0.4% of the Danish surgical patients, 2.8% of US surgical patients, and 5.3% of 241 New York children who were routinely sent for genetic and heart checks (that group included pigeon chests). The 2024 Pectus Care Guidelines estimate about 5% of people with apparently isolated pectus are later diagnosed with Marfan. Marfan can affect the heart and the aorta, the body’s main artery, so a diagnosis is worth having.

Noonan, Loeys-Dietz and Turner

In 107 people with gene-confirmed Noonan syndrome across four hospitals in South India, 54% had pectus excavatum. Loeys-Dietz showed the same rate in a Johns Hopkins series: 35 of 65 patients, and 16 of those 65 had first been diagnosed with Marfan. In Turner syndrome a broad “shield” chest is typical, and a 1993 study of 15 girls found mild pectus excavatum in 3.

Ehlers-Danlos syndrome

Pectus excavatum is reported more often in some types of Ehlers-Danlos syndrome (EDS), mostly in small studies and one survey. Most people with pectus excavatum don’t have EDS. In a global online survey, 125 of 3,360 people with hypermobile EDS (3.7%) said they had pectus excavatum, against 0.1% in an unmatched comparison group. A 2021 review cites a small series in which 6 of 20 people with classical or vascular EDS had mild pectus. That’s an association, not a cause, and an earlier version of this page overstated it.

Klinefelter syndrome

I couldn’t find a study measuring how often pectus excavatum occurs in Klinefelter syndrome. When I searched PubMed in October 2026, it had just two records mentioning both: a 2004 case report and a 2020 Dutch series on tall children in which the child with pectus had Marfan, not Klinefelter. Klinefelter affects about 1 in 450 to 600 male births, according to a 2026 review, and usually makes boys tall. My reading: shared tall stature is the likely reason they get linked. If you have both, tell your doctor.

When pectus excavatum develops after birth

A few cases appear or worsen after a specific event. All are rare.

• Open-heart surgery. A Beijing study of 49 children who needed the Nuss procedure after heart surgery concluded that pectus can develop or worsen afterwards. An international study of 75 patients from 14 centres, also co-authored by Prof. Yüksel, found repair came a median 6.4 years later, and the heart was accidentally injured during it in 7%. Neither study shows the heart surgery caused each case, but this group needs an experienced chest wall surgeon.
• Diaphragmatic hernia at birth. A Japanese study found pectus in 19 of 159 survivors; a Manitoba population study found no more than in other children.
• A blocked airway in infancy. A baby’s chest is soft, and breathing hard against a blockage pulls it inward. In 137 US children with laryngomalacia, a floppy voice box, 9 (6.6%) had pectus excavatum. Two children in a 1981 report improved after their adenoids and tonsils came out. A chest that pulls in with each breath isn’t a fixed dip; pectus excavatum in babies and children explains the difference.
• SMA type 1. In a small series of infants with this nerve and muscle disease, pectus appeared in untreated babies whose chest sank in with each breath, and resolved with night-time breathing support.
• Premature birth. I couldn’t find a study linking it to classic pectus excavatum. A Buenos Aires study of 4,640 chest wall patients described a separate rib pattern, equally common with or without preterm birth.

What doesn’t cause it

None of these has been shown to cause pectus excavatum:

• Posture. I couldn’t find a study showing bad posture causes it. In 268 Istanbul patients aged 10 to 18 with a sunken or pigeon chest, in a study also co-authored by Prof. Yüksel, 90.3% had a forward head and 81.7% rounded shoulders. It was a single snapshot, and the authors read it as the chest affecting posture. More in pectus excavatum and posture.
• Body weight. In the Istanbul surgical group, 32.5% were underweight. That’s an association, and the study can’t say which way it runs.
• Exercise or lifting. I couldn’t find a study that tested it.
• Sleeping position or mattress. I couldn’t find one either, as I explain in the best sleeping position for pectus excavatum.
• Smoking, yours or your mother’s in pregnancy. I couldn’t find a study testing either as a cause. Smoking has other reasons to stop, covered in smoking with pectus excavatum.

Can it be prevented?

No. Cleveland Clinic says that until a specific cause is found, you can’t prevent it. The only exceptions are narrow: night-time breathing support for babies with SMA type 1, and treating a young child’s blocked airway. For everyone else, there was nothing to do differently.

When the cause matters: genetics checks and red flags

For most people, finding the cause won’t change anything. For some it matters a lot, because a connective tissue disorder can affect the heart and blood vessels.

The 2024 Pectus Care Guidelines say a first assessment should cover the eyes, heart, skeleton and family history. Anyone who might have an inherited connective tissue disorder should be referred to a genetics service, a Class I recommendation, the guideline’s strongest grade. For them, surgery should wait until a geneticist has looked.

Signs that point that way: being tall with long limbs and fingers, a high-arched palate, mitral valve prolapse (a heart valve that bulges as it closes), scoliosis, very flexible joints, flat feet, short-sightedness in childhood, easy bruising and slow healing. Timing matters too. At a Rotterdam clinic, 8 of 18 children under 11 with pectus had a genetic finding. In the New York study, 20% of children with a mixed sunken-and-pigeon chest had Marfan.

To rule out a syndrome, a doctor may order chromosome studies, enzyme tests or metabolic studies, MedlinePlus says. With isolated pectus and none of these features, the Amsterdam review says further genetic tests usually aren’t needed.

See a doctor before you start any device, brace or exercise program if any of these apply to you:

• chest pain
• fainting or nearly fainting
• breathlessness at rest or with light effort
• palpitations or an irregular heartbeat
• a diagnosed heart or lung condition
• Marfan syndrome or Ehlers-Danlos syndrome, or a doctor has raised either
• previous chest surgery
• a Haller index above 3.25 together with symptoms
• symptoms that nobody has checked yet

None of these means you’ll need surgery. They mean someone should look at your heart and lungs before you go further. An index above 3.25 is a common referral threshold, not an emergency.

The emergency signs are listed in pectus excavatum symptoms.

What to do next

Pick your line:

• No family history, no syndrome signs, noticed at puberty. The cause is unknown, and it isn’t anything you did.
• It runs in your family. Tell your doctor. No one can give your children a percentage yet.
• You recognise several of the signs above, or it started before 11. Ask your doctor about a genetics referral.
• It appeared after heart surgery. See a chest wall specialist before anything else.

Knowing why matters less than knowing how significant yours is, and the free pectus assessment helps you work that out. The cause may stay unknown for years; your next step doesn’t have to wait.

Sources

1. Cleveland Clinic. Pectus excavatum. Updated 2023. Read it
2. Kloth K, et al. Eur J Pediatr Surg. 2022;32(4):316-20. Read it
3. Kuru P, et al. Korean J Thorac Cardiovasc Surg. 2016;49(1):29-34. Co-authored by Prof. Mustafa Yüksel. Read it
4. Creswick HA, et al. J Pediatr Surg. 2006;41(10):1699-703. Read it
5. Horth L, et al. J Pediatr Genet. 2012;1(3):161-73. Read it
6. Media AS, et al. J Thorac Dis. 2021;13(3):1652-7. Read it
7. Cobben JM, Oostra RJ, van Dijk FS. Eur J Med Genet. 2014;57(8):414-7. Read it
8. Ranjan R, et al. Curr Issues Mol Biol. 2026;48(1):122. Read it
9. Janssen N, et al. J Thorac Dis. 2024;16(2):1687-1701. Read it
10. Nakaoka T, et al. J Pediatr Surg. 2010;45(10):2015-8. Read it
11. Eisinger RS, et al. J Surg Res. 2019;235:93-7. Read it
12. David VL. J Clin Med. 2022;11(5):1241. Read it
13. Park CH, et al. Thorac Cardiovasc Surg. 2015;63(5):427-32. Read it
14. Kondo S, et al. Pediatr Surg Int. 2020;36(3):305-16. Read it
15. MedlinePlus Medical Encyclopedia. Pectus excavatum. Reviewed 2025. Read it
16. Nuss D, Obermeyer RJ, Kelly RE. Ann Cardiothorac Surg. 2016;5(5):493-500. Read it
17. MedlinePlus Genetics. Marfan syndrome. Read it
18. Fraser S, Child A, Hunt I. Pediatr Rep. 2018;9(4):7277. Read it
19. Kelly RE, et al. Ann Surg. 2010;252(6):1072-81. Read it
20. Behr CA, et al. J Pediatr Surg. 2019;54(9):1926-8. Read it
21. Dunning J, et al. The pectus care guidelines. Eur J Cardiothorac Surg. 2024;66(1):ezae166. Read it
22. Athota JP, et al. BMC Med Genet. 2020;21(1):50. Read it
23. Erkula G, et al. J Bone Joint Surg Am. 2010;92(9):1876-83. Read it
24. Mehta AV, et al. Chest. 1993;104(6):1795-9. Read it
25. Daylor V, et al. J Clin Med. 2025;14(16):5636. Read it
26. Chohan K, et al. Chron Respir Dis. 2021;18:14799731211025313. Read it
27. Lauffer P, et al. Ned Tijdschr Geneeskd. 2020;164. Read it
28. Anaforoğlu İ. Front Endocrinol. 2026;17:1848181. Read it
29. Chen C, et al. J Pediatr Surg. 2018;53(10):1964-9. Read it
30. Jaroszewski DE, et al. Eur J Cardiothorac Surg. 2017;52(4):710-7. Co-authored by Prof. Mustafa Yüksel. Read it
31. Takayasu H, et al. Pediatr Int. 2016;58(9):877-80. Read it
32. Markel M, et al. Pediatr Surg Int. 2022;38(5):731-6. Read it
33. Schaerer D, et al. Int J Pediatr Otorhinolaryngol. 2013;77(10):1721-3. Read it
34. Fan L, Murphy S. Am J Dis Child. 1981;135(6):550-2. Read it
35. Bach JR, Bianchi C. Am J Phys Med Rehabil. 2003;82(10):815-9. Read it
36. Toselli L, et al. J Pediatr Surg. 2025;60(1):161971. Read it
37. Kahraman Esen H, Yüksel M. Med Sci Monit. 2026;32:e952511. Co-authored by Prof. Mustafa Yüksel. Read it
38. Billar R, et al. Eur J Pediatr Surg. 2024;34(4):325-32. Read it