A Missouri mother and father are behind bars after they allegedly forced their “very thin” 4-year-old son to sit in a dog crate as the rest of the family ate dinner.

Patricia L. Siercks, 34, and Joshua J. Gusman, 32, stand accused of the child abuse of their son. According to a probable cause affidavit by the Clinton Police Department, doctors determined the boy was “within days of fatal organ failure.”

The investigation began when cops responded to Golden Valley Memorial Hospital in late June for a report of child abuse involving a 4-year-old boy. The victim was “very thin” and had bruises and scratch on his face.

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The boy”s medical chart stated he had gained just one pound in 2 1/2 years, the affidavit said. Siercks allegedly told deputies that “she spends $400 on food” but claimed her son is “picky.” The boy’s doctor ordered his parents in November to feed him the nutrition drink PediaSure to help him gain weight. It worked: He gained nearly 7 pounds by March, per the affidavit.

But Siercks stopped giving him the drink because “it was all the victim wanted to have,” the affidavit said. As a result, the boy lost 6 pounds between March and June. The victim weighed just 23 pounds, making him more than 20 pounds underweight, cops noted.

Siercks allegedly admitted to hitting her son in the face about two weeks prior because he was “throwing a fit” at an appointment. She said she “became frustrated, angry, and then slapped and punched the victim in the face,” per the affidavit.

“Siercks used her right hand and slapped across the left side of the victim’s face and then using her right hand punched the left side of the victim’s face in the temple/eye area,” detectives wrote.

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The boy was admitted to a children’s hospital on June 30 due to his weight and heartbeat rhythm, which was thrown off by the malnutrition, cops said. Doctors diagnosed the boy with refeeding syndrome, a condition resulting from prolonged starvation that could be fatal if the boy resumed eating rapidly or suddenly.

After receiving his Miranda warnings, Gusman apparently denied any abuse. But he previously admitted to a Child Protective Service investigator that he saw the boy “placed into a dog crate while the family ate dinner and the victim was not provided any food,” the affidavit said. He also allegedly said Siercks was abusing the boy for two years; for example, he would hear a commotion in another room and would find Siercks “assaulting” their son and he would intervene to stop it, according to the affidavit.

In addition to the refeeding syndrome, doctors diagnosed the boy with “acute childhood torture, long-term starvation, imbalanced electrolytes due to dehydration, and stunted growth.”

Cops arrested Siercks and Gusman last week. They remain at the Henry County Jail without bond. Siercks has a court appearance scheduled for Tuesday while Gusman was slated to appear before a judge on Monday morning.