Extraordinary changes in behavior in an infant after a brief separation

A previously healthy 8-month-old infant experienced a dramatic change in affect, motor patterns, and appetite after a brief (4-day) separation from her parents. She went from being a happy, interactive, and engaging child to being withdrawn, with limited vocalization, spontaneous motor activity, or interest in her environment. For the first 3 days after her parents returned home, she refused solid food and most of the formula or water she was offered. Over the following week, her appetite increased minimally. Her parents were concerned about her apathy, excessive quietness, and lack of interest in food, toys, or their own attempts to engage her in play. At the pediatrician's office, she was significantly less interactive and playful compared with previous visits. Her temperature, heart rate, and respiratory rate were normal. Although there were no objective signs of dehydration, her weight was 8 ounces less than the previous recorded weight 1 month ago. Results of the physical examination were normal, with the exception of neurological and behavioral findings. She had mild, generalized decreased tone and strength, with normal deep tendon reflexes, a sad facial appearance with sustained furrowing of the lines in her forehead, difficulty in eliciting a social smile, and limited spontaneous sounds. There was an absence of focal neurological findings, a flat open anterior fontanel, and a head circumference measurement consistent with previous recorded results. There were no cutaneous bruises, and findings of her funduscopic examination did not reveal retinal hemorrhage. Before the 4-day holiday, child care was provided almost exclusively by her mother at home. On only two previous occasions, at 4 and 6 months of age, this first child of 20-year-old high school graduate parents was cared for by a neighbor when the parents went out to a movie theater. She cried for about 10 minutes when the parents left on these occasions. Her mother stated that she felt anxious about leaving the child for several days, but she and her husband decided that they needed a break and planned the 4-day vacation. Child care was provided by the neighbor, who did not notice any unusual behavior or refusal to feed while in her care during the parents' absence.