What is Poland anomaly?
Poland anomaly is a congenital condition — meaning it is present from birth — in which the pectoralis major muscle on one side of the chest is partially or completely absent. The pectoralis major is the large muscle that spans the front of the chest and connects the shoulder to the sternum. In Poland anomaly, this muscle either did not develop fully or did not develop at all on one side.
In many cases, the condition also involves differences in the hand and fingers on the same side: webbing between fingers, shortened fingers, or a smaller hand. The nipple, breast tissue, and ribcage on the affected side may also be involved. The right side is affected in approximately 75% of cases.
Poland anomaly is not life-threatening. It does not affect the heart, lungs, or other internal organs in the vast majority of cases. It does not shorten life expectancy. People with Poland anomaly live full, active lives — including careers in athletics, medicine, law, and every other field.
Poland anomaly is not a disease and it is not progressive. It will not get worse over time. The physical features are present from birth and remain stable, though they may become more noticeable during puberty as the body develops around them.
What are the names for this condition?
You may encounter three terms that all refer to the same condition:
- Poland anomaly — the currently preferred medical term, used in this site and recommended by the AISP 2020 consensus guidelines
- Poland syndrome — the older and still widely used name; you will see this in most published research and in most online communities
- Poland sequence — used by some clinicians to emphasize that the various features all result from one original developmental disruption
The condition is named after Sir Alfred Poland, a British surgeon who described it in 1841. Poland Foundation uses "Poland anomaly" as the primary term because it most accurately reflects the medical understanding of the condition — but all three terms are correct and widely understood.
What does Poland anomaly look like?
Poland anomaly looks different from person to person. The defining feature — the absent or underdeveloped pectoralis major — may be subtle or obvious depending on the degree of involvement and the individual's body type.
In children, it is often first noticed as a visible asymmetry in the chest: one side appears flatter or less developed than the other. The nipple on the affected side may be smaller, positioned differently, or absent. In males, the chest wall asymmetry may become more noticeable as the opposite side develops muscle mass during adolescence. In females, breast asymmetry often becomes the most visible feature during puberty.
When the hand is involved, the differences can range from mild webbing between two fingers to more significant shortening of the fingers and a smaller overall hand size on the affected side.
How common is Poland anomaly?
Poland anomaly is classified as a rare condition, occurring in approximately 1 in 20,000 to 30,000 births. In the United States, that means roughly 150 babies are born with Poland anomaly each year. Males are affected about twice as often as females. The right side of the body is involved in approximately 75% of cases, though no reliable explanation for the side preference has been established.
Because Poland anomaly is rare and its features can be subtle — especially in mild cases — it is often missed at birth and diagnosed much later. The average age of diagnosis is 14 years, and only about 32% of cases are identified at birth. Many adults discover they have Poland anomaly as teenagers or adults, sometimes after years of wondering why one side of their body looks different.
What parts of the body can Poland anomaly affect?
Poland anomaly primarily affects structures on one side of the body. The features vary significantly from person to person — some individuals have only the chest muscle involvement, while others have a broader range of differences. Common features include:
- Pectoralis major muscle — absent or underdeveloped; the defining feature of the condition
- Pectoralis minor muscle — often also underdeveloped or absent on the affected side
- Hand and fingers — webbed fingers (syndactyly), shortened fingers (brachydactyly), or a smaller hand (symbrachydactyly) on the affected side; present in a significant minority of cases
- Ribs — partial absence or abnormal development of the ribs on the affected side; less common
- Breast and nipple — smaller, differently positioned, or absent nipple and breast tissue on the affected side; in females, this often becomes the most visible feature during puberty
- Forearm — occasionally shorter or differently developed on the affected side in more complex presentations
Not every person with Poland anomaly has all of these features. The condition spans a wide spectrum, from very mild (barely visible chest asymmetry, no hand involvement) to more complex presentations. A person's position on the spectrum does not predict which other features may or may not be present.
Is Poland anomaly only on one side?
Yes — Poland anomaly is unilateral, meaning it affects only one side of the body. The opposite side develops normally. This one-sidedness is one of the condition's defining characteristics and reflects the localized nature of the vascular disruption that causes it.
The asymmetry this creates — one side of the chest, hand, or breast developing differently from the other — is often what first draws attention to the condition. It is also what makes Poland anomaly particularly visible during puberty, when the unaffected side is developing normally while the affected side is not.
Is Poland anomaly genetic? Will it affect other children?
In the vast majority of cases, Poland anomaly is not genetic. It is sporadic — it occurs by chance, not through inherited genes, and it does not typically run in families. Having one child with Poland anomaly does not meaningfully increase the likelihood of it occurring in another pregnancy.
For a full explanation of what causes Poland anomaly and why neither parent is responsible, see our causes page.
What is the ICD-10 code for Poland anomaly?
The ICD-10 code for Poland anomaly is Q79.8 — Other congenital malformations of the musculoskeletal system. This code is important for insurance documentation, medical records, and specialist referrals. If you are navigating insurance coverage for surgery or treatment, having this code documented in your child's records can support your claim.
What happens next after a diagnosis?
A diagnosis of Poland anomaly is the beginning of a process, not a verdict. Most families find that the weeks immediately after diagnosis are the most overwhelming — the condition is unfamiliar, the terminology is new, and it can be hard to know what to ask or where to turn.
A few practical starting points:
- Find a specialist — Not every pediatrician or general physician has experience with Poland anomaly. A pediatric plastic surgeon, pediatric orthopedic surgeon, or pediatric geneticist with experience in this condition can provide a thorough evaluation and guide next steps. Our provider directory lists specialists across the US.
- Understand the spectrum — Poland anomaly varies widely. A thorough evaluation will clarify which features are present and how significant they are. Many mild cases require no intervention at all.
- Connect with other families — The Poland Foundation community forum connects families who are navigating the same questions. Hearing from parents and adults who have been in your position can be more useful than anything a website can tell you.
- There is no urgency in most cases — Poland anomaly is stable, not progressive. In most situations, there is time to learn, gather information, and make thoughtful decisions. Emergency intervention is rarely required.