We report the case of a 19-year-old male who was brought to our psychiatry consultation by his family for behavioural disorders and poor school performance of years of evolution.

We found ourselves before a tall, thin, childish, suspicious, perplex, inhibited and minimizer patient, so we sent him to our hospital for psychiatric admission, where he showed a flowery delirium of mystic, religious and megalomaniac content; complex visual and auditory hallucinatory phenomena; and where he was diagnosed of acute polymorphic psychotic disorder and autism spectrum disorder with marfanoid habit. Therefore, we suspected a Lujan–Fryns syndrome and requested genetic confirmation. Risperidone was prescribed as solo treatment, with a rapid control of the symptoms.

Lujan–Fryns syndrome, first described in 1984, corresponds to a sequence mutation in exon 22 of med12 gene of chromosome X. It is hard to suspect and diagnose before puberty. Those affected have marfanoid habit and also other psychiatric manifestations such as autistic behaviour, mild-moderate mental retardation (there are some reported cases with normal intelligence), language disorders, emotional instability, aggressiveness, hyperactivity, shyness which can be extreme, obsessive-compulsive disorder, isolation, delusions, visual and auditory hallucinations, and there are cases that describe schizophrenia. Its diagnosis requires adequate physical and psychopathological examination, and it is established with clinical suspicion and genetic confirmation. There are very few cases described and there is little bibliography available about Lujan–Fryns syndrome [1].

The authors have not supplied their declaration of competing interest.