Psychiatric Symptoms as the First or Solitary Manifestation of Somatic Illnesses: Hyperammonaemia Type II

Aim: We describe the difficulties encountered in making a diagnosis where a somatic condition manifests itself alongside psychiatric symptoms associated with possible psychiatric comorbidities.

Methods: A case study is presented of a 15-year-old girl who was eventually diagnosed with ornithine transcarbamylase (OTC) deficiency (hyperammonaemia type II), following an initial diagnosis of pervasive developmental disorder, selective mutism, and anorexia nervosa.

Results: The OTC disease is not fully expressed in females and its prevalence is lower than in males. Around 17-20% of female patients found with a defective OTC gene on an X chromosome can suffer from OTC deficiency that may result in elevated levels of ammonia in the blood; this occurs when one of the X chromosomes become inactivated. Patients typically present with nausea, migraines, and a history of dietary protein avoidance. In more severe cases, ataxia, confusion, hallucinations, and cerebral oedema can occur. The OTC deficiency can thus remain undiagnosed in women for many years.

Conclusion: Somatic comorbidity in psychiatric inpatients is commonly found; however, such disorders are rarely diagnosed or even treated adequately.

Keywords: Anorexia nervosa; Autism spectrum disorder; Delirium; Hyperammonaemia type II; Ornithine transcarbamylase (OTC) deficiency; Psychiatric comorbidity; Selective mutism.