Imagine a mix of screwball comedy and heartbreak. Imagine a disease so strange and a family so dysfunctional it takes a while to discern the pain beneath the denial. Imagine a Chekhovian tragi-comedy in a Pee-wee Herman world.

		'Kimberly Akimbo' Where: The Rep, Pittsburgh Playhouse, 222 Craft Ave., Oakland. When: Through Feb. 13; Wed.-Sat. 8 p.m.; Sun. 2 p.m. Tickets: $18-$22; student and senior discounts; 412-621-4445.

If this imagining seems like too much work to a dubious end, you'll be relieved to hear that someone has done it for you, with a big comic payoff. In "Kimberly Akimbo," David Lindsay-Abaire imagines just such a world. And under the direction of John Amplas, The Rep, Point Park University's professional company at the Pittsburgh Playhouse, has staged it with due attention to both the guffaws and the tragedy.

City Theatre had a similar experience three years ago with Lindsay-Abaire's "Fuddy Meers." There, the disease of the central character, played by Helena Ruoti, caused her to awake every day without memory to rebuild her world from scratch. In "Kimberly Akimbo," the central character, played by Shirley Tannenbaum, has a disease that ages her at 4¹*₂ times the usual rate. A high school student, she looks 70.

Obviously both plays play with time, using it to put pressure on life to open up deep recesses not usually visible.

"Kimberly Akimbo" embodies this in a moon-like wall clock. In Pei-Chi Su's purposefully goofy sitcom set in the intimate Studio Theater, the clock's numbers jumble at its bottom. But as the play progresses, the hands speed forward, setting each of 14 scenes at a specific time and even allowing you to count the days, should you be so inclined.

The story that unspools over a couple of weeks (the dialogue indicates some time jumps the clock can't show) focuses on Kimberly Levaco, who is celebrating her 16th birthday as the play begins. Pattie, her pregnant hypochondriacal mother, and Buddy, her drunken, irresponsible father, seem to have forgotten her birthday, but Debra, her foul-mouthed ex-con aunt, shows up with a present.

This 16th birthday is more significant than most, because, as Kimberly's friend, geeky Jeff, discovers, 16 years is the average life expectancy of her disease.

That's awful, but a woman of Kimberly's apparent age using the language and gestures of a teen is funny. So is this horrible New Jersey family, who gradually reveal evidence of sympathetic if baffled humanity. We watch them aghast but amused, identifying entirely (if skittishly) with Kimberly, who seems the most adult of them all.

Gradually, too, we piece together whatever it was that caused the family to leave Secaucus in a hurry, settling in Bogota (pronounced buh-GO-da), where Buddy mans the cashier's booth at a Chevron station. The revelation is awful, but it dramatizes the poignant humanity beneath the selfishness.

It's easier to describe heartbreak than comedy, but that's what "Kimberly Akimbo" primarily is -- a comedy. Granted that a lot of the laughs have a dark flip-side, they are definitely laughs. And Lindsay-Abaire's inventive wit also comes up with such devices as tape-recorded advice to Pattie's expected baby and a visible symbol of the family's ongoing struggle with swear words.

Playing full-bellied comedy of dysfunction without scanting humanity takes acting grounded in character. Amplas' finely directed cast meets the challenge with deadpan naturalism. Nobody knows he or she is funny; nobody condescends to his or her absurdities; and everyone stays in the moment, which is how we discover they are people, not just comic constructs.

In a memorable, landmark performance, Tannenbaum feelingly plays Kimberly's teenage hope, despair and embarrassment, letting a sidelong glance, tilt of the head or drooping eyelids express depths of emotion.

Philip Winters' stolid Buddy is the first of the grotesques to win our sympathy, partly because Buddy stops drinking, but mainly because Winters suggests Buddy's implicit heart. The reality beneath the self-absorption of Nancy Bach's Pattie comes more slowly into focus, because Lindsay-Abaire exploits her comedy longer.

Debra is the play's most broadly comic figure, and Sheila McKenna makes every outrageous line plausible. John Magaro's Jeff is believably precocious as Kimberley's friend and foil.

Some inter-scene music by Douglas Levine sets an ironically bouncy sitcom tone, and Susan O'Neill's costumes score character-true laughs -- Buddy's snow hat -- or touch the heart -- as when Kimberly dresses up like a grandmother.

It is Jeff, an aficionado of the "puzzleistic arts," who derives the anagram "cleverly akimbo" from Kimberly's name. Akimbo she is, with such a disease and family. The considerable grace she exhibits is an inspiration justifying the temporary rebirth at the play's end.