Le syndrome de Fahr est défini par la présence de calcifications intracérébrales, bilatérales et symétriques, non artériosclérotiques, localisées aux noyaux gris centraux. L’une de ces principales étiologies est la pseudohypoparathyroïdie (PHP), qui témoigne d’une résistance à l’action de la parathormone (PTH), avec surtout une hypocalcémie et un taux normal à élevé de PTH. Nous rapportons dans ce travail, l’observation d’un homme de 36 ans atteint de PHP, révélée par un syndrome de Fahr, découvert après plusieurs années d’évolution de troubles psychiatriques et neurologiques persistants et réfractaires aux traitements. Chez ce patient, l’alcoolisme, l’utilisation de neuroleptiques classiques, d’agents anticholinergiques ou encore de certains antiépileptiques ont contribué, par différents mécanismes, à la pérennisation et l’exacerbation des symptômes. Ce travail souligne l’intérêt de la recherche des troubles du métabolisme phosphocalcique en présence de manifestations neuropsychiatriques, afin de dépister une PHP ou toute autre étiologie d’un syndrome de Fahr et d’adopter ainsi, les mesures thérapeutiques les plus appropriées.

Fahr’s syndrome is characterized by the presence of intracerebral, bilateral and symmetrical non-arteriosclerotic calcifications, located in the central grey nuclei. One of its main etiologies is pseudohypoparathyroidism (PHP), due to a resistance to the action of parathormone (PTH) with essentially hypocalcaemia and a normal or a high rate of PTH.

Mr B.A. is a 36-year-old man, admitted to hospital because of refractory psychotic symptoms associated with alcohol abuse and fits of convulsion, for diagnostic and therapeutic update. Mr B.A. had presented convulsions since the age of 10, without regular medical treatment. He showed a decrease in his school performances and started using alcohol. Since the age of 17, he began expressing delusions of persecution and of enchantment fed by the persistence of the convulsions. He was administered phenobarbital, and classic antipsychotics (haloperidol and levomepromazine) and developed serious extrapyramidal side effects, treated with an anticholinergic (trihexyphenidyl). Evolution was rather disadvantageous: more epileptic fits, exaggeration of tremors; abuse of alcohol and persistence of psychotic symptoms. On admission, psychiatric examination objectified paranoid delusions of being possessed and persecuted by others. Neurological examination revealed the presence of limb tremors, with a positive Froment’s sign on the right, and dysarthria. Other than this, the patient was shorter in comparison with his siblings and exhibited bad dentition. A CT brain scan found bilateral, symmetric basal ganglia calcifications, confirmed by MRI, in favour of Fahr’s syndrome. Phosphocalcic investigations revealed a low concentration of serum calcium (65mg/l) and a hyperphosphataemia (60.1mg/l). The blood level of parathyroid hormone was in the upper limit of normal (66ng/l), and levels of thyroid hormones and thyroide-stimulating hormone were normal. The diagnosis of Fahr’s syndrome, revealing a pseudohypoparathyroidism was posed, and the patient was orientated to endocrinology after readjustment in his therapy (sodium valproate and olanzapine).

About 40% of the patients with Fahr’s syndrome are seen with primarily cognitive and other psychiatric findings. For this patient, hypocalcaemia was at the origin of his convulsions, and the use of phenobarbital, known for its hypocalcemiant action, provoked the inverse result. Alcohol drinking also aggravated hypocalcaemia, and maintained the fits. The use of classic antipsychotics and anticholinergic agents, amplified the extrapyramidal signs caused by Fahr’s syndrome. Recognizing the origin of the symptoms allowed rethinking the therapeutic strategy according to all these elements.

Psychiatrists should consider Fahr’s syndrome as a differential diagnosis in the evaluation of psychosis associated with convulsions. This case, along with others in the literature, further emphasizes the importance of the role of neuro-imaging and the search for disrupted phosphocalcic metabolism in patients with atypical or refractory psychotic symptoms.