"Little People, Big World" star Tori Roloff is responding to questions about why her 3-month-old son, Josiah, is often seen with his tongue out in photos.
Roloff addressed the subject after several fans left comments on a recent Instagram post celebrating Josiah's first 12 weeks of life.
"A larger tongue is a characteristic achondroplasia," Roloff, 31, wrote. "He will grow into it."
Dr. John Pappas, director of clinical genetic services at NYU Langone's Hassenfeld Children's Hospital, offered a different take.
"It's not that the babies have larger tongues, it's the way that the face is developing. The middle of the face is underdeveloped and the tongue appears to be larger," Pappas told TODAY Parents. "As they grow, the face develops and will accommodate the tongue.
This typically happens at around 2 or 3 years old.
Josiah and his siblings, Jackson, 5, and Lilah, 2, have achondroplasia, the same type of dwarfism their dad, Zach Roloff, has.
Achondroplasia is a skeletal abnormality, according Pappas. The hallmarks of the condition include short stature and short bones of the limbs. If a parent has achondroplasia, then there's a 50% of having a baby with achondroplasia.
Adult height in people with achondroplasia is about 4 feet, 3 inches for men, and 4 feet, 2 inches for women.
"But nowadays, we have new therapies and medications that can make individuals with achondroplasia taller," Pappas added.
Tori and Zach, 32, welcomed their third child on April 30.
On July 30, Tori revealed that Josiah, a.k.a. "Si," is "finally sleeping" through the night and weighs nearly "13 pounds."
"Si is tracking and LOVES his brother! He loves being talked to!" Tori captioned an Instagram carousel. "Josiah still doesn't give away smiles easily though! Bath is still our favorite time!"
Earlier this year, Tori told Us Weekly that she and Zach "try not to make a big deal" out of Josiah's dwarfism.
"He's Josiah. He has achondroplasia, but he's not, like, Josiah the achondroplasia," Zach explained.