Medically reviewed by Angela Sheddan, FNP
Written by Our Editorial Team
Last updated 3/10/2023
Have you noticed your hairline is beginning to recede and take on a more triangular shape? There are numerous potential causes of a receding hairline, including male pattern baldness and a far less common form of hair loss called temporal triangular alopecia.
Temporal triangular alopecia, or congenital triangular alopecia (CTA), is a form of hair loss that involves your hairline taking on a triangular pattern.
It often only affects one side of your scalp, although about 20 percent of people develop hair loss on both sides of their hairline.
Although it can look similar to a receding hairline, there are several major differences between temporal triangular alopecia and male pattern baldness, including treatment options.
Below, we’ve discussed what temporal triangular alopecia is, as well as the common signs you may notice if you’re affected by this form of hair loss.
We’ve also explained what causes temporal triangular alopecia to develop, as well as the steps that you can take to treat this type of alopecia and restore your hairline.
Temporal triangular alopecia is a form of non-scarring alopecia that involves the development of a triangular patch of hair loss, usually around your frontotemporal scalp (the front of your scalp, or hairline area).
Within this patch of bald skin, healthy hair follicles may be replaced by vellus hair follicles — thin, miniaturized hair follicles that are less able to grow terminal hairs (typical scalp hairs) and create a normal hair density level.
If you have this type of hair loss, you might notice your hairline receding significantly on one or both sides of your scalp.
Most cases of temporal triangular alopecia involve triangular areas of hair loss. However, some people with this condition develop oval-shaped or rectangular hair loss around the hairline and scalp.
These areas of hair loss may feature small vellus hairs — thin, fine hairs similar to the hairs that grow on your face and other parts of your body.
It’s common for temporal triangular alopecia to develop in children. However, some people also develop this form of hair loss as adolescents or during adulthood.
Unlike many other types of hair loss, temporal triangular alopecia is non-progressive, meaning it usually doesn’t become more severe over time.
Temporal triangular alopecia isn’t very common. In fact, research suggests that just 0.11 percent of the population — or around one in every 1,000 people — have this condition.
Experts have been aware of temporal triangular alopecia for more than a century, as it was first described in 1905. However, the precise causes of temporal triangular alopecia still aren’t completely understood.
Some researchers think that this form of alopecia is congenital, meaning it’s present in affected people from birth. However, it seems that many cases of temporal triangular alopecia are acquired, or develop later in life.
Other experts have suggested that temporal triangular alopecia may be caused by abnormal or incomplete development of the epidermis, which is the outermost layer of skin.
Although the precise cause of temporal triangular alopecia isn’t known, experts in skin and hair have identified certain disorders and syndromes that often occur at the same time as this condition. These include:
Abnormalities that affect your bones and/or teeth
Certain types of birthmarks and skin pigmentation issues
Neurological disorders, such as epilepsy or Dandy-Walker syndrome (DWS)
Hypospadias (abnormal development of the urethral opening in boys)
Dysaesthesia (an abnormal sense of touch) in hairless areas
Leukonychia (white discoloration that affects the nails)
Recurrent bronchiolitis (lung infection in young children)
Down syndrome and other forms of intellectual disability
Woolly hair nevus (coiled, hypopigmented hair)
Hydronephrosis (swelling of the kidneys)
Congenital heart diseases and defects
Congenital hip dislocation (CHD)
Iris nevi (freckles on the eyes)
Noonan syndrome with multiple lentigines
Phakomatosis pigmentovascularis (PPV)
If you have one of the above disorders or syndromes and also begin to notice signs that you're losing hair or a clear patch of alopecia around the frontotemporal region of your scalp, it’s important to talk to your healthcare provider.
Because temporal triangular alopecia and androgenetic alopecia (a clinical term for male pattern baldness) can both lead to a similar pattern of hair loss around your hairline, it’s easy to mistake one type of hair loss for the other.
However, temporal triangular alopecia and male pattern hair loss aren’t the same, meaning treatments for one form of hair loss may not help with the other.
Key differences between temporal triangular alopecia and male pattern baldness include:
Temporal triangular alopecia isn’t caused by DHT. Male pattern baldness occurs as a result of the hormone dihydrotestosterone (DHT) attaching to receptors in your scalp and causing your hair follicles to shrink, or miniaturize.
Currently, there’s no high quality evidence to suggest that temporal triangular alopecia is caused by DHT, or that people with this type of frontotemporal hair loss have higher DHT levels than average.
Male pattern baldness typically causes an even receding hairline. Although it’s fairly common to have some asymmetry in your hairline, most men with male pattern hair loss notice hairline recession that’s roughly the same on the left and right sides.
On the other hand, temporal triangular alopecia is often unilateral, meaning it may occur on one side of your hairline but not the other.
Temporal triangular alopecia is usually diagnosed early in life. Male pattern hair loss is more common in older men, as the effects of DHT can accumulate over time and harm your hair follicles. By age 40 to 49, around half of all men are affected.
In contrast, temporal triangular alopecia is usually diagnosed early in life. Most people are diagnosed as children, typically between three and nine years of age. However, it can, and occasionally does, develop in adults.
Temporal triangular alopecia typically only occurs near the hairline. Male pattern baldness varies in severity, from a receding hairline to a bald patch around your crown to near-total baldness. The severity of hair loss is measured using the Norwood Scale.
In contrast, temporal triangular alopecia almost always affects areas near your hairline, such as your temples and/or frontal scalp.
Temporal triangular alopecia affects men and women. Although pattern hair loss is found in men and women, it’s more common in men, who generally have higher levels of testosterone and other androgen hormones, such as DHT.
Temporal triangular alopecia has no gender predilection, meaning it occurs in men and women at approximately the same rate.
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If you’re worried that you might be developing triangular temporal alopecia as an adult, one of the first things you should do is to talk to your healthcare provider.
Because triangular temporal hair loss isn’t common, they may suggest seeing a dermatologist (a doctor that specializes in the skin, hair and nails).
To diagnose triangular temporal alopecia, a dermatologist will talk to you about your symptoms, perform a physical examination and look at your scalp.
They may also use a device called a polarized light handheld dermatoscope to check your hair follicles for signs of this type of hair loss.
Because triangular temporal alopecia doesn’t occur due to DHT, hair loss medications such as finasteride don’t stop this form of hair loss or produce hair regrowth in affected areas.
There’s also only very limited evidence that topical minoxidil — a medication that’s used to treat several common forms of hair loss — offers benefits for this form of localized alopecia.
In other words, the usual medications for hair loss in men may not be helpful if you have a thin, triangular hairline due to temporal triangular alopecia.
Currently, the most effective way to treat this form of hair loss is through hair transplant surgery, a procedure that involves surgically removing healthy hair follicles from the back and sides of your scalp, then relocating them to your hairline.
Hair transplantation can vary in price and complexity based on the severity of your hair loss and a range of other factors. Performed effectively, a hair transplant can “fill in” empty areas of your hairline and give you a natural-looking pattern of hair growth.
You can learn more about this form of hair restoration surgery, as well as its costs, benefits and potential side effects, in our guide to hair transplants.
Temporal triangular alopecia can take a serious toll on your hairline, causing a triangular patch of hair loss on either one or both sides.
Because this form of hair loss is very easy to mistake for male pattern baldness, there are a few things you’ll want to keep in mind if you’re concerned you may be developing temporal triangular alopecia:
First, it’s important to talk to your healthcare provider. They’ll be able to look at your scalp and let you know if you have temporal triangular alopecia or a more common type of hair loss.
Second, most hair loss medications aren’t effective. If you have temporal triangular hair loss, taking a DHT-blocking medication like finasteride isn’t likely to have any effect on your hair density in affected areas.
Third, you aren’t to blame for this form of hair loss. Although experts aren’t yet fully sure about what causes triangular hair loss, there’s no scientific evidence that suggests that the way you care for your hair has any effect.
Not sure if you have temporal triangular alopecia or male pattern baldness? Take part in a hair loss consultation online via our telehealth platform to learn more about what could be causing your hair loss, as well as your options for promoting healthy hair growth.
You can also find out more about dealing with hair loss in our guides to alopecia types and the best ways to treat them, how a diagnosis for hair loss works and medications that could cause you to lose hair.