Sometimes, a funny thing happens when Dr. Roberta Pagon looks directly into the sun. She sneezes. Not just once though, but usually three times.

She's not the only one in her family who sneezes when sunlight hits their face -- two of her children also react by sneezing three times in a row. And now a grandchild does it, but only sneezes once.

Odd coincidence? Not really, says Pagon, a pediatrician in the division of genetic medicine at Seattle Children's Hospital. This tendency to sneeze at sunlight is known as the "photic sneeze reflex," and it's hereditary.

Not only is there a genetic basis for "sun sneezing," Pagon says the number of times people sneeze in response to light also appears to run in families.

This scientific discovery happened in a very unscientific way. Pagon and her genetics colleagues were sitting at the same table during a birth defects conference when the conversation shifted to discussing the sun and sneezing. Much to their surprise, they learned that 4 out of 10 of them were affected by this strange reaction. "One person said it was common for people in his family to sneeze five times; in my family it was three times, and another person said once," recalls Pagon.

They quickly did what years of medical training had taught them -- they coined an acronym for it:  ACHOO syndrome, or Autosomal Dominant Compelling Helio-Ophthalmic Outburst. Autosomal dominant stands for the way the 'sneeze gene' is inherited; an individual has a 50-50 chance of passing this trait on to a child. "Compelling" because it was well, interesting, or at the very least, quirky. "Helio" meant sun, "ophthalmic" meant eye, and "outburst" the end result. They even wrote up a paper about the peculiar phenomenon.

Although this reaction might seem unusual, it's not that uncommon. By one estimate,18% to 35% of people get a tickling sensation in their nose when their eyes meet intense sunlight. Some folks may also get this weird response to bright artificial light, such as the eye doctor's or dentist's light or a photographer's flash.

Driving out of a tunnel may trigger the reflex or leaving a movie theatre on a summer's day, says Nicolas Langer, PhD, a neuropsychology researcher the University of Zurich, who has studied the photic sneeze reflex. Often "it's just the change of a dark location to a bright (very sun exposed) location" that brings on the reflex, he explains. 

In his research published in the journal PLoS ONE, Langer compared the visual reactions of 10 sun sneezers to 10 people without this reflex. Volunteers were hooked up to an EEG machine so the scientists could measure their brain and neural responses when exposed to bright light.

Their results suggest that "the 'photic sneeze reflex' is not a classical reflex that occurs only at a brainstem or spinal cord level," says Langer. "It seems to involve other cortical areas" of the brain.

As for why it happens, Langer offers two theories. One is that the visual system in the brain is more sensitive in photic sneezers. When it gets overstimulated by light, this co-activates regions representing the nose (the somatosensory system), which then triggers a sneeze.

A second possibility is that two nerves (the optic nerve and trigeminal nerve) are too close together in photic sneezers. Langer says light may cause stimulation of the optic nerve in the eye, which then coactivates the trigeminal nerve in the face, and results in an achoo reaction.

Solar sneezes could be an occupational hazard if you're an airplane pilot, baseball outfielder, sky diver, punt-return specialist, or high-wire acrobat. But for roughly one of out four people, it's merely something curious that makes them a little different from the next guy or gal.

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The pen is said to be mightier than the sword. But an unusual case report has shown that a pen may be mightier than stomach acid.

The case, which appeared in the British Medical Journal Case Reports, described a 76- year-old British woman sent to a GI specialist because of weight loss and diarrhea.

She was diagnosed with severe diverticulosis, a condition that's common in older people in which small pouches bulge out from the colon. But when doctors did a scanning test of her belly they noticed something strange: "A linear foreign body in the stomach." (Click here for photos.)

When asked about it, the woman remembered accidentally swallowing a black felt-tip pen 25 years earlier. (In case you're wondering, dentures and toothpicks are two of the most common items that adults accidentally swallow.)

According to her gastroenterologist Dr. Oliver Waters, who authored the case report, she was standing on her stairs using an uncapped pen to poke a spot on her tonsils. She was also holding a hand mirror to guide the pen to the exact spot. Somehow, while doing this, she lost her balance and stumbled. The fall managed to push the pen down her throat. It glided down her gullet and found a home in her tummy.

She told her husband and her doctor what had happened, but they were skeptical of the story. X-rays done at the time were normal and found no trace of the pen. Flash forward to the present, to a different doctor and even better stomach-scanning technology to investigate the case of the missing marker. More than two decades later a scan hit pay dirt: The pen.

Although the woman's current digestive problems had nothing to do with the marker she had unintentionally downed, doctors decided to remove it anyway. Their rationale was a case in the medical literature of a child accidentally swallowing a ball-point pen that bore a hole in his bowel. Incredibly, the pen had stayed in her stomach for 25 years without causing any significant damage to her GI tract, Waters says.

After bathing in stomach acid for a two-and-a-half decades, the pen was corroded and the plastic was flaky, but, amazingly, the pen still had usable ink and could write!

"This case highlights that plain abdominal x-rays may not identify ingested plastic objects and occasionally it may be worth believing the patient's account however unlikely it may be," the report advises doctors.

Write on!

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There's really no other way to put this: During a Pilates stretching exercise, a 59-year-old woman said her body "swallowed" one of her breast implants. Sounds like something we just made up, but the woman's case is the subject of an unbelievable report, just published online in the latest New England Journal of Medicine. 

The woman was a breast cancer survivor who'd had a double mastectomy, and afterward had gotten breast implants. During a Pilates routine, she was doing a Valsalva maneuver, a breathing technique in which a person takes a deep breath and holds it while bearing down. (In other words, you're going through the motions of exhaling forcibly, but without letting any air escaping through the mouth or nose.)

Doing a Valsalva maneuver increases pressure inside your chest cavity. In this lady's case, enough pressure built to essentially send her right implant through the thin tissue between her ribs and into the space in between the lungs. This left her more perplexed than anything -- where did it go?! Fortunately (and incredibly), she said upon arriving in the the emergency department of the Johns Hopkins Hospital in Baltimore that she wasn't experiencing any chest pain or shortness of breath. 

"I can picture how this could happen in a freak occurrence," says Dr. Anthony Youn, a Michigan-based cosmetic surgeon and frequent contributor to msnbc.com, who didn't treat this patient but gave us his professional opinion on what the heck happened here.

Note that Youn called this a "freak occurrence" -- this is not exactly going to happen to your average Pilates lover, as this woman's case had some extra complications. She'd recently undergone a surgery to repair her heart's mitral valve, a procedure that typically involves some separating of the muscles that run between the ribs. 

"What likely happened in this instance is that the breast implant was placed under the chest muscle and on top of the ribs, an extremely common practice in breast reconstruction," Youn says. "When the patient Valsalva'd, the pectoralis (chest) muscle likely contracted and pushed the implant through the space between her ribs," which was particularly fragile after the valve surgery.

"The weakened scar tissue was easily torn, and the strength of the pectoralis muscle pushed the implant deep into her chest," Youn explains. 

The woman was treated at Johns Hopkins, where surgeons retrieved the implant from within her chest and put it back where it belonged. 

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Doctors at Queen's University in Kingston, Ontario, have spotted what looks like the face of a screaming man in an ultrasound of a testicular tumour.

A mystical image or sheer coincidence? Either way, that’s one sad ‘nad.

Doctors in Canada were scanning through ultrasound images of a 45-year-old man with a painful mass in his testicles when they did a doubletake. There was a man's face staring up at them, the mouth grimacing as if he were in agony.

"It looked like a man screaming in pain, which I thought was hilarious considering the clinical picture of the poor guy," Dr. G. Gregory Roberts, School of Medicine at Queen's University, Kingston, Ontario, told msnbc.com.

Roberts and urologist Dr. Naji J. Touma reported their amazing discovery -- which ranks right up with the grilled cheese Madonna or pancake Jesus -- in a recent issue of the medical journal Urology.

In the article, "The Face of Testicular Pain: A Surprising Ultrasound Finding," the doctors revealed that, upon spotting the distinctive tumor, a "brief debate ensued on whether the image could have been a sign from a deity (perhaps "Min" the Egyptian god of male virility; however, the consensus deemed it a mere coincidental occurrence rather than a divine proclamation." 

People have seen holy images in all kinds of random items, but this is certainly a bizarre appearance in a gonad ultrasound.

 "Ultrasounds are just a bunch of pixels that occasionally look like recognizable things, such as faces. But I have never seen such a perfect image before," Roberts said.

 The article, which reportedly was meant as a little inside joke between urologists known more for helping guys with their erecticle dysfunction and prostate problems than rip-roaring sense of humor, has metastasized -- umm, gone viral.

Touma told the Montreal Gazette that the doctors informed the patient about the image but that he wasn't very interested in the remarkable mirage. "I think the patient was just relieved it wasn't cancer," the newspaper reported.

In the end, the patient opted for an orchiectomy (removal of the testicle) and the tumor was found to be benign.

What's the weirdest image you've ever seen in an unexpected place?

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How old are you? Spit it out! A new UCLA study shows that your age can accurately be predicted from, of all things, your saliva.

It's not as ridiculous a scientific endeavor as you might initially guess. The researchers, led by principal investigator Dr. Eric Vilain, explain that the finding could serve as a forensic tool for crime scene investigators to accurately pinpoint the age of a suspect, narrowing the age of a suspect to a five-year range.

"Regular DNA analysis at a crime scene gives information on the characteristics of the person that are immutable," explains Vilain, a professor of human genetics, pediatrics and urology at the David Geffen School of Medicine at UCLA. The "immutable" characteristics he lists are things like a person's DNA sequence and how it matches with suspects. But Vilain explains that the "spit test" could give investigators valuable information on a characteristic that changes with time, which "could help the investigators zoom in on the right people."

To find saliva's age-predicting power, Vilain and his team of UCLA geneticists used a process called methylation, a chemical modification of the DNA, which is influenced by our environment -- the food we eat, the toxins we're exposed to, "and, as it turns out, time passing," Vilain says. 

"When methylation happens at certain places in the DNA, it tells certain genes to turn on or turn off. So the sequence of the genes themselves is not modified, but their expression is," he explains. "What we found is that the degree of methylation at a small number of places in the human genome is linked to our age. The correlation is high enough that we can predict what the age of a person is by just having access to a sample of their saliva."

The weirdest part about this very weird research: "It was an accidental finding," admits Vilain. He and a team of researchers rounded up 34 pairs of identical, male twins, ages 21 to 55, for a study on differences in methylation when it comes to predicting a person's sexual orientation. That study was a bust, from a scientific point of view -- but it did lead them to finding the spit test for age. They used saliva samples to scour the twins' genomes, and identified 88 sites on their DNA that correlated methylation to age. (They repeated the findings in non-twins -- 31 men and 29 women ages 18 to 70.)

They then identified the top two genes with the genes that were most highly correlated to age, and used those to build a predictive model that could correctly predict the person's age within five years.

We're talking about a very small sample of saliva -- about 0.1 ounces, Vilain says. Thanks to this unexpected finding, he's now surprised to be asking himself research questions inspired by an episode of "CSI": "Can we do it with saliva on a cigarette butt?"

Follow msnbc.com health writer Melissa Dahl on Twitter.

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