Betamethasone therapy in ataxia telangiectasia: unraveling the rationale of this serendipitous observation on the basis of the pathogenesis.

Ataxia telangiectasia (A-T) is a rare autosomal recessive disorder characterized by progressive neurological dysfunction. To date, only supportive care aimed to halt the progressive neurodegeneration is available for the treatment. Recently, an improvement of neurological signs during short-term treatment with betamethasone has been reported. To date, the molecular and biochemical mechanisms by which the steroid produces such effects have not yet been elucidated. Therefore, a review of the literature was carried out to define the potential molecular and functional targets of the steroid effects in A-T. Glucocorticoids (GCs) are capable of diffusing into the CNS by crossing the blood-brain barrier (BBB) where they exert effects on the suppression of inflammation or as antioxidant. GCs have been shown to protect post-mitotic neurons from apoptosis. Eventually, GCs may also modulate synaptic plasticity. A better understanding of the mechanisms of action of GCs in the brain is needed, because in A-T during the initial phase of cell loss the neurological impairment may be rescued by interfering in the biochemical pathways. This would open a new window of intervention in this so far incurable disease.

Efficacy of very-low-dose betamethasone on neurological symptoms in ataxia-telangiectasia.

BACKGROUND: Ataxia-telangiectasia (A-T) is a non-curable neurodegenerative disorder, associated with progressive neurological dysfunction, oculocutaneous telangiectasia, immunodeficiency, predisposition to cancer and radiosensitivity. A recent study documented improvement in neurological symptoms after a short-term therapy with betamethasone in patients with A-T. Aim of this study was to evaluate the minimum therapeutically effective dosage of betamethasone on neurological symptoms of A-T. METHODS: Six responsive patients with A-T, received two 20-day cycles of oral betamethasone at 0.01 and 0.03 mg/kg/day (10% and 30% of the previously used full dosage), each followed by a 20-day washout period. Clinical and laboratory evaluations were carried out at T0 and at the end of each cycle. Neurological assessment was performed through the Scale for the Assessment and Rating of Ataxia (SARA). The glucocorticoid-induced leucine zipper (GILZ) and glucocorticoid receptor (GR) RNA expression were evaluated before and during the trial through real-time PCR. RESULTS: SARA scores significantly improved in all patients at the dosage of 0.03 mg/kg/day. In particular, three patients exhibited an improvement in 5/8 variables and two patients of 7 and 8 variables, respectively. Furthermore, the clinical improvement was already evident after the lower dosage. The basal GILZ and GR RNA expression were significantly lower in patients than in controls. GILZ expression increased in all patients after the beginning of the therapy, whereas no correlation between GR and the response was found. CONCLUSION: Our data indicate that betamethasone is effective in A-T at a minimal dosage and that GILZ may be a useful biomarker of the clinical response. This study provides Class IIIA evidence that betamethasone at very low dosage is effective in improving neurological signs of patients affected with ataxia-telangiectasia.