“My Little Sister,” a tender domestic drama from the Swiss writers and directors Stéphanie Chuat and Véronique Reymond, faces terminal illness with a refreshing emotional candor.

Lisa (Nina Hoss), a gifted Berlin playwright, stopped writing on the day that her beloved twin brother, Sven (Lars Eidinger), a celebrated theater actor, received his leukemia diagnosis. Since then, she’s been living in artistic limbo in Switzerland, where her husband (Jens Albinus) teaches at a prestigious boarding school. But the demands of Sven’s illness, and Lisa’s inability to accept his decline, only tug her closer to her brother and further from her fracturing marriage.

Distinguished by a modestly discreet directing style that allows the actors to shine, “My Little Sister” offers neither false uplift nor dreary realism. The photography is bright and lustrous, the tone vital and purposeful. Eidinger plays Sven entirely without self-pity, a man furiously seizing public-restroom sex as if willing his depleted body to perform. And Hoss makes Lisa a ball of anxious industry, her denial and distress keeping her in constant motion. Both siblings, more than anything, want Sven back onstage; they have always been each other’s muse.

Absolving the film of any shred of sentimentality, the indispensable Marthe Keller, as the twins’ testy mother, delivers her sometimes shockingly unfiltered remarks with a pique that softens their cruelty. Small in scale and big in heart, “My Little Sister” believes unwaveringly in the palliative power of art: When medicine can’t heal you, sometimes words can fill the breach.

My Little Sister
Not rated. In German and French, with subtitles. Running time: 1 hour 39 minutes. Watch on Film Movement.