'How are you?'

"What happened to me…" a friend said, looking at me, still somewhat shocked. I braced myself, as he wasn't someone easily flustered. "Maybe it's something for your column," he added with a thin chuckle.

A while ago, he'd met a new neighbor. They'd had a pleasant chat at his house about this and that, and hadn't seen each other since.

One afternoon, a few months later, he was walking down his street and met a woman who stopped him with the most-asked question in the world: “How are you?” He didn’t know the woman, and as he considered the standard formula to respond, he wondered feverishly, “Who is this?”

He noticed that she knew him well enough to casually mention his first name during their conversation. He acted as if nothing was wrong, realizing he could hardly ask, "Who are you, anyway?"

They exchanged a few more pleasantries and then parted amicably. Stunned, he continued his walk. Didn't she, in retrospect, seem somewhat familiar after all, he wondered? Was she perhaps an acquaintance from a few years ago whom he'd never seen again? He couldn't figure it out, cursed his failing memory—and gave up.

A little while later, he saw the same woman enter the apartment building next to his. Good heavens, this was his chance. He trotted over to her at a daring pace for his age and called out, "Can I ask you something?" She stood there, embarrassed.

"I have a confession to make," he said. "We were talking on the street the other day, and I didn't know exactly who you were, but I didn't dare say it. I see now that you live here."

She looked at him blankly and asked, "But you knew that, didn't you? That I'm your neighbor? I've already been over to meet you!"

He stood before her, stunned. "Sorry...sorry," he could only mumble. And then: "I really didn't remember. Now that you mention it, I do remember that conversation at home, very vaguely, but I'd completely forgotten the face that went with it."

It was an unpleasant observation for her as well, he knew, as he whipped up a few explanatory excuses off the cuff. "At your age, you might expect that more often," she said without snappiness. She was about twenty years younger than him. "Luckily, I recognized you this time," he said as they parted with a vague greeting.

At home, he searched the internet for what might be wrong with him. He came across a word he hadn't heard of: prosopagnosia, or face blindness, the inability to recognize faces, even those of people he knows, sometimes even his own in a mirror. It can be congenital, but it can also develop, temporarily or otherwise, due to an illness (stroke, tumor, dementia) or a brain injury after an accident.

As many as one in fifty people suffer from it. The question now was: was he the one? "If I ever stop greeting you, you'll know what's going on," my friend said resignedly.