Delayed Diagnosis of Painless Thyroiditis in an Adolescent Presenting with Aggression and Disruptive Behavior Initially Attributed to Worsening of a Psychiatric Disorder.

Painless thyroiditis, which is rare in children, exhibits the characteristic sequence of hyperthyroidism, including aggressive and disruptive behaviors. Unlike subacute thyroiditis or Graves' disease, painless thyroiditis is challenging to diagnose because of its mild symptoms and minimal or absent physical findings. Moreover, aggressive and disruptive behaviors in children with psychiatric disorders may be misconstrued as exacerbation of underlying symptoms. The present patient was a 16-year-old male with adjustment disorder who presented to a pediatric psychiatric clinic for assessment of irritability. After 4 months, he developed aggressive and disruptive behaviors that prompted initiation of risperidone but without improvement. After 1 month, he reported palpitations and dyspnea. His neck was supple and non-tender without thyroid enlargement. Thyroid studies revealed elevated free T4 and T3 levels and suppressed thyroid-stimulating hormone level, suggesting hyperthyroidism. A radioactive iodine uptake test revealed a barely visible thyroid gland, consistent with thyroiditis. Painless thyroiditis, without thyroid tenderness, was diagnosed. We describe a case of painless thyroiditis in an adolescent patient with aggressive and disruptive behaviors that were initially attributed to worsening of an underlying adjustment disorder. Even when minimal or no signs of hyperthyroidism are present, painless thyroiditis should be considered in the differential diagnosis of children with aggressive and disruptive behaviors. Awareness of potential anchoring bias is also recommended to prevent its delayed diagnosis of such behaviors.