Simian crease: one line across the palm instead of two
A simian crease is one line across the palm in place of two. Many healthy people have one. See what it is, how common it is and what palmistry made of it.
Two separate creases
The usual pattern. 84 to 91% of palms in the three surveys we could open.
Single crease
The two have merged. Often called a simian crease in older sources.
Sydney crease
The lower crease reaches the far edge of the palm.
Suwon crease
The upper crease crosses the palm. First named in Korea in 2010.
A simian crease is one line across the palm where most people have two. It's an outdated name, and the medical term is single transverse palmar crease, so that's what we'll use from here on. The two main creases have merged into one. Many healthy people have this, and it is not a diagnosis of anything.
You may have noticed it on your own hand, or on your baby's, or a doctor may have used the word. MedlinePlus, the US National Library of Medicine's reference, says that "having a single palmar crease is often normal", and that it appears "in about 1 out of 30 people". The rest of this page goes through how common it is, what it can appear with, and what palmistry made of it. If you're asking about your child, there's a short note for you below.
What's the proper name?
Single transverse palmar crease, or single palmar crease. A 2009 paper setting out standard terminology for the hands and feet defines it this way: "The distal and proximal transverse palmar creases are merged into a single transverse palmar crease." The same entry retires the older word, because "that term is disparaging and less descriptive".
The old name came from a likeness to the palms of non-human primates, which is why it's fallen out of use. People still search for simian crease and simian line, and some older medical pages still say it, so we keep it in this page's title to help people find it. In palmistry the same two creases are called the head line and the heart line.
How common is it?
The honest answer is a range, and it's a wide one. Here is every figure we could open, with who was studied.
| Source | Who | Found |
|---|---|---|
| MedlinePlus, 2025 | General reference, no sample given | about 1 in 30 |
| Wikipedia, secondary | "General population" estimate | 1.5 to 3% |
| Belay et al., 2022 | 832 students at the University of Gondar, Ethiopia, counted by palm: 1,664 palms | 5.0% of palms |
| Ranjit et al., 2019 | 252 students and staff of a teaching hospital in Kathmandu | 7.7% |
| Ali, Pakistan | 4,000 outpatients at one hospital, January 1999 | 1.3% |
| Park et al., 2010 | 3,216 volunteers in Suwon, Korea, counted by palm: 5,196 palms | 12.6% of palms |
- Ali, Pakistan
- Wikipedia, low
- Wikipedia, high
- MedlinePlus
- Belay, Ethiopia
- Ranjit, Kathmandu
- Park, Korea
Why would careful counts differ by this much? We can see a few reasons in the papers themselves.
- They count different things. Belay and Park count palms, so one person can appear twice. Others count people.
- They study different groups. Wikipedia's sources say it's more common in East Asian and Native American populations, and each sample here comes from one place.
- They draw the categories differently. Papers don't agree on the edges of these patterns. Park's 2010 classification and Biesecker's 2009 terminology describe the Sydney crease in different words, and a hand near the line may land in different boxes.
- Sex shifts the figure as well. MedlinePlus says males are twice as likely as females to have one. In Belay's sample it's 5.6% of male palms and 3.4% of female palms.
Conditions it can appear with
This is usually why people arrive here, so here's the plain list. MedlinePlus says a single palmar crease "may also be associated with" conditions that include:
- Down syndrome
- Aarskog syndrome and Cohen syndrome
- Fetal alcohol syndrome and rubella syndrome
- Trisomy 13 and cri du chat syndrome
- Turner syndrome and Klinefelter syndrome
- Pseudohypoparathyroidism
Being "associated with" runs in one direction, and that direction matters. The crease is found in about 45% of people with Down syndrome, according to Wikipedia's sources. That says how often people with Down syndrome have the crease. It doesn't say how often people with the crease have Down syndrome, which is a very different number and a far smaller one, because the crease also turns up in large groups of ordinary students, like the 5% of palms at Gondar. Those Ethiopian authors make this point: variant patterns "do not necessarily always signify abnormality in genetic property".
So the crease isn't a test. When there is a question about one of these conditions, MedlinePlus says that diagnosis is "based on a family history, medical history, and complete physical exam". A doctor looks at a whole person. A line on a hand can be one small thing they note along the way.
If you're asking about your child or yourself
It's natural to worry when you notice something on your baby's hand or hear an unfamiliar word at an appointment. A single palmar crease on its own is often normal. If you have any questions at all, bring them to your pediatrician or doctor, even if it feels like a small thing to ask. They can look at everything together, tell you what they see, and answer what no web page can. Please don't try to settle it from a photo or from this site.
One hand or both
It can be on either or both. In the Pakistani hospital sample, 1% of outpatients had it on one hand and 0.3% on both. Among the Ethiopian students, 93.1% had the same crease pattern on both palms, single or otherwise, so hands often match, though not always. That's all we can honestly report. Figures from a single clinic aren't rules, and we found nothing that tells a particular person what one hand or two would mean. That's a good question for a doctor, if it's on your mind.
It also forms very early. Wikipedia's entry, citing a 1971 study, says the crease appears around the second month of gestation, before the hand's movements begin. Whether it runs in families is something we couldn't get a clear, sourced answer on, and we'd rather say so.
What palmistry made of it
Cheiro, in 1916, described "one deep, straight line" across the hand in which "the two lines both Head and Heart appear to blend together", and he read it as head and heart acting as one: "If such a subject loves, he unites with it all the forces of his mind." He told readers to check whether it lies where a head line or a heart line would. That's tradition, and it has no more evidence behind it than any other palm reading. It tells you nothing about anyone, and we've left the rest of what he said about it out of this page.
Check your own hand
This check asks what you can see and shows you which drawing it matches. You can also read about how the frequencies compare with other marks, if you're curious.
Open your hand and look at the long creases running across it. Answer for what you can see.
Two separate creases
The usual pattern: 90.8% of palms among 832 students in Ethiopia and 90.1% of 252 people in Kathmandu.
This is a description of a shape, based on what you ticked. It says nothing about your health or anyone else's. If a doctor has mentioned a crease to you, or you're asking about your child, that conversation belongs with them.
The scan can trace your creases on a photo. It sometimes notes a possible single crease, and it misses some. It's a shape, never a diagnosis.
To work from a real photo, the line tracer lets you place your creases on it, and the palm scanner traces the main ones by itself. It sometimes flags a possible single crease, misses others, and can never tell you anything about your health.
Sources
- Single palmar crease
- Biesecker LG et al. Elements of morphology: standard terminology for the hands and feet
- Belay DG et al. Prevalence of palmar crease patterns among students at University of Gondar, Ethiopia
- Ranjit N et al. Palm creases analysis in students and staff of a teaching hospital in Kathmandu
- Ali M. Prevalence of simian crease in general population
- Park JS, Shin DS, Jung W, Chung MS. Improved analysis of palm creases
- Single transverse palmar crease
- Cheiro, Palmistry for All
One crease or two, the reading works from what's there
If your hand has a single crease, the Complete Palm Reading reads it as a shape with a tradition behind it, and never as a diagnosis. Medical questions belong with a doctor.
Complete Palm Reading$9.99One payment. No subscription.
Questions people ask
- What is a simian crease?
- One crease running across the palm where most people have two. The medical term is single transverse palmar crease: the distal and proximal transverse creases are merged into one. Simian is an older name that medicine has moved away from.
- Is a simian crease normal?
- Often, yes. MedlinePlus says having a single palmar crease is often normal, and it appears in about 1 out of 30 people. Many healthy people have one.
- Does a simian crease mean Down syndrome?
- No. It's more common in people with Down syndrome, but having the crease doesn't mean a person has Down syndrome or any other condition. Many people with the crease have no condition at all. A diagnosis comes from a medical history and a physical exam.
- How common is a single palmar crease?
- Estimates vary with the group studied. MedlinePlus says about 1 in 30. Wikipedia gives 1.5 to 3% of the general population. Samples we read range from 1.3% of 4,000 outpatients at one hospital in Pakistan to 12.6% of 5,196 palms from 3,216 volunteers in Korea.
- My baby has a single palmar crease. Should I worry?
- On its own it's often normal. If you're worried, or if a doctor mentioned it, ask your pediatrician. They look at the whole child, which a single line on a hand can't replace.
- Why is it called simian? What is the proper name?
- Because it resembles the usual palm of non-human primates. A 2009 paper on standard terminology replaced the term with single transverse palmar crease, calling the old term disparaging and less descriptive.
- Does it matter if it's on one hand or both?
- We found no rule that a person can use. In one hospital sample, 1% had it on one hand and 0.3% on both. That's one clinic and can't tell you anything about a particular person. Questions about it go to a doctor.
- What does a single line mean in palmistry?
- Palmistry reads the head and heart lines as one, in a person who brings feeling and thought to bear together. That's a tradition with nothing tested behind it. Nothing about it should worry you.
- Is a single palmar crease inherited?
- We didn't find a source we trust that gives a simple answer, so we won't guess. A doctor or genetic counselor can speak to it for your family. Researchers do report that it differs between populations and that it forms very early, before the fingers start moving in the womb.
One line or two, it's your hand.
Scan your palm to see your own creases traced on your own photo.