Abstract
The thrombocytopenia-absent radius (TAR) syndrome is a rare disorder characterized by the bilateral absence of the radii and thrombocytopenia [1]. Other features include ulnar or humeral abnormalities, phocomelia in severe cases, variable lower limb involvement, short stature, cow's milk intolerance and congenital heart disease [1]. There is considerable overlap with other syndromes with radial aplasia such as Roberts syndrome, Holt–Oram syndrome, Fanconi anaemia, thalidomide embryopathy and Rapadilino syndrome [2]. Neuropsychiatric abnormality is not commonly reported in the TAR syndrome. Mental retardation secondary to intracranial bleeding and epilepsy has been described [2], but not psychosis.
We report the case of a 21-year-old man with TAR syndrome who developed a brief schizophreniform psychosis with affective features. In addition to absent radii, he had dysmorphic features in the form of low set ears, micrognathia, broad forehead and short stature. He had a low platelet count (90×109 L−1) but gave no history of intracranial bleeding. He had no cardiac or genitourinary abnormalities. There was no family history of TAR syndrome or a psychiatric disorder.
His perinatal history was unremarkable. Motor development was delayed but cognitive development was normal. His academic performance at school was average. He was bullied and ostracized by other children and failed to establish a supportive social network. He moved to another major city for a new beginning but came under increasing stress over 18 months from lack of continuous employment and support relationships. About 2 weeks before admission, he developed persecutory ideation against his family and grandiose delusions that he earned millions. He wandered aimlessly and appeared perplexed. There was no report of hallucinations. Following disorganized and intrusive behaviour on a plane, he was hospitalized involuntarily. His CT brain scan was normal. He was treated with risperidone 1 mg/day and diazepam 5 mg/day with rapid improvement in 4 days. He was continued on this medication for 6 months with no recurrence of psychotic symptoms.
Although a chance association cannot be ruled out, TAR syndrome may have neurobiological abnormalities predisposing to psychosis. Hypoplasia of the cerebellar vermis and corpus callosum was recently reported in this syndrome [3], suggesting that intracranial haemorrhage may not be an adequate explanation for the neuropsychiatric disorders. The genetics of TAR syndrome are under active investigation. TAR syndrome is considered to be autosomal recessive in inheritance although occurrence in families may be due to germinal mosaicism for a new dominant mutation. Two abnormal karyotypes were reported in one study [2]: 46, XY, dup(8)(p23.1p23.1) and 46, XY, t(1;7)(q42;p15). Cloning of the translocation point at 7p and the identification of candidate genes is one of the aims of genetic studies of TAR syndrome [2] that may well inform psychosis research.