Functional neurological symptom disorders (FNSD) pose a common challenge in clinical practice, particularly in pediatric cases where the clinical phenotypes can be intricate and easily confused with structural disturbances. The frequent coexistence of FNSDs with other medical disorders often results in misdiagnosis. In this review, we highlight the distinctions between FNSD and various psychiatric and neurological conditions. Contrary to the misconception that FNSD is a diagnosis of exclusion, we underscore its nature as a diagnosis of inclusion, contingent upon recognizing specific clinical features. However, our focus is on a critical learning point illustrated by the case of a 14-year-old male initially diagnosed with FNSD, but subsequently found to have a rare primary monogenic movement disorder (paroxysmal kinesigenic dyskinesia, PKD). The crucial takeaway from this case is the importance of avoiding an FNSD diagnosis based solely on psychiatric comorbidity and suppressible symptoms. Instead, clinicians should diligently assess for specific features indicative of FNSD, which were absent in this case. This emphasizes the importance of making a diagnosis of inclusion. Extended follow-up and clinical-oriented genetic testing might help identify comorbidities, prevent misdiagnosis, and guide interventions in complex cases, which cannot be simply classified as "functional" solely because other conditions can be excluded.
Keywords: Functional neurological symptom disorder; conversion disorder; paediatric dystonia; paediatric movement disorder; proline-rich transmembrane protein 2.
Understanding and Avoiding Mistakes in Diagnosing Children with Functional Neurological Symptom Disorders: A Review and Case Report: This article discusses Functional Neurological Symptom Disorders (FNSDs), focusing on misdiagnosis, differential diagnosis, and other diagnostic challenges, particularly in pediatric cases. FNSDs involve motor or sensory symptoms that are inconsistent over time and unexplained by neurological disease, often associated with psychosocial factors. The article highlights the complexity of distinguishing FNSDs from other neurological and psychiatric conditions, emphasizing the importance of careful evaluation. The authors review various conditions that can mimic FNSDs, such as epileptic seizures, syncope, and different motor disorders. They emphasize the need to consider psychiatric conditions in the differential diagnosis, including factitious disorders, and malingering. The article presents a case study of a 14-year-old with involuntary movements, initially diagnosed as having a Functional Movement Disorder. After careful evaluation, the patient was diagnosed with a genetic dystonia (PRRT2 mutation). The case shows the importance of not rely solely on psychological problems, bizarre presentations or suppressible symptoms when diagnosing FNSDs.