Safety and Efficacy of Botulinum Toxin in the Treatment of Self-Biting Behavior in Lesch-Nyhan Disease.

BACKGROUND: Lesch-Nyhan disease (LND) is a disease of purine metabolism linked to chromosome X due to the absence or near-absence of enzyme hypoxanthine-guanine phosphoribosyltransferase. Patients with LND have a compulsive autoaggressive behavior that consists of self-mutilation by biting. METHODS: The objective of this study was to explore the safety and efficacy of botulinum toxin (BoNT) injected into the masticatory muscles and biceps brachii to reduce self-mutilation in patients with LND. We retrospectively analyzed six patients with LND who were treated with BoNT to prevent automutilatory behavior. RESULTS: The patient ages when started on treatment with BoNT were 4, 4.5, 6.6, 7.9, 13.9, and 32.3 years. Patients received a mean number of injections of 20, ranging from 3 to 29, over a period that ranged from 1.5 to 7.1 years. The maximum total dose of Botox was 21.3 units/kg mean and the maximum total dose of Dysport was 37.5 units/kg mean. A total of 119 injections were performed. Of these 113 (95%) were partially or completely effective. Only three of 119 injections (2.5%) produced adverse effects. CONCLUSIONS: Botulinum toxin is useful and safe for the treatment of self-biting behavior in patients with LND.

Distribution and genotype-phenotype correlation of GDAP1 mutations in Spain.

Mutations in the GDAP1 gene can cause Charcot-Marie-Tooth disease. These mutations are quite rare in most Western countries but not so in certain regions of Spain or other Mediterranean countries. This cross-sectional retrospective multicenter study analyzed the clinical and genetic characteristics of patients with GDAP1 mutations across Spain. 99 patients were identified, which were distributed across most of Spain, but especially in the Northwest and Mediterranean regions. The most common genotypes were p.R120W (in 81% of patients with autosomal dominant inheritance) and p.Q163X (in 73% of autosomal recessive patients). Patients with recessively inherited mutations had a more severe phenotype, and certain clinical features, like dysphonia or respiratory dysfunction, were exclusively detected in this group. Dominantly inherited mutations had prominent clinical variability regarding severity, including 29% of patients who were asymptomatic. There were minor clinical differences between patients harboring specific mutations but not when grouped according to localization or type of mutation. This is the largest clinical series to date of patients with GDAP1 mutations, and it contributes to define the genetic distribution and genotype-phenotype correlation in this rare form of CMT.