El reto del diagnóstico comórbido en psiquiatría infantojuvenil

The case is presented of a patient with a changing behavioural phenotype and a rare biotype, who was diagnosed with attention deficit hyperactivity disorder (ADHD) from an early age, with partial response to the prescribed treatment (extended-release methylphenidate, risperidone, sertraline). After an aggressive episode at home, he was admitted to the child and adolescent hospitalisation unit. A brain NMR scan and a metabolic study revealed anomalies compatible with a deficiency of ornithine transcarbamylase (OTC), an enzyme which forms part of the urea cycle. The study discusses the different diagnoses that were proposed given the syndrome of the patient, both from an organic approach, as well as and from the perspective of psychiatric comorbidity. OTC deficiency has a low incidence -one in every 15,000 newborn babies-, similar to that of phenylketonuria (which was included years ago in the newborn screening program in Spain). This is a predominantly hereditary disease (X-linked transmission), but with several described cases of de novo mutations or deletions. Complete OTC deficiency shows its symptoms in the first years of life, whereas a partial deficiency could start during late childhood or even in adolescence, with unspecific neuropsychiatric or behavioural symptoms. A clear pattern has not been established.