Epidemiology of seropositive myasthenia gravis in Sardinia: A population-based study in the district of Sassari.

INTRODUCTION/AIMS: The global incidence and prevalence of myasthenia gravis (MG) range between 6-31/million and 10-37/100,000, respectively. Sardinia is a high-risk region for different immune-mediated disorders, but the epidemiology of MG remains unclear. We determined the epidemiology of MG with acetylcholine receptor (AChR)-immunoglobulin G (IgG) and muscle-specific tyrosine kinase (MuSK)-IgG in the district of Sassari (North-Western Sardinia; population, 325,288). METHODS: From the laboratory of the University Hospital of Sassari (reference for AChR/MuSK-IgG testing in Sardinia since 1998) and the main neurology units in Sardinia, we retrospectively identified MG patients with (1) AChR-IgG and/or MuSK-IgG positivity by radioimmunoprecipitation assay; and (2) residency in the district of Sassari. Incidence (January 2010-December 2019) and prevalence (December 31, 2019) were calculated. RESULTS: A total of 202 patients were included (incident, 107; prevalent, 180). Antibody specificities were AChR (n = 187 [93%]) and MuSK (n = 15 [7%]). The crude MG incidence (95% confidence interval) was 32.6 (26.8-39.2)/million, while prevalence was 55.3 (47.7-63.9)/100,000. After age-standardization to the world population, incidence decreased to 18.4 (14.3-22.5)/million, while prevalence decreased to 31.6 (26.1-37.0)/100,000. Among incident cases, age strata (years) at MG onset were: <18 (2%), 18-49 (14%), 50-64 (21%), and ≥65 (63%). DISCUSSION: Sardinia is a high-risk region for MG, with a prevalence that exceeds the European threshold for rare disease. Identification of the environmental and genetic determinants of this risk may improve our understanding of disease pathophysiology.

A minimal physiologically based pharmacokinetic model for high-dose methotrexate.

PURPOSE: High-dose methotrexate (HDMTX) is administered for the treatment of a variety of malignant tumors. Wide intra- and inter-individual variabilities characterize the pharmacokinetics of MTX, which is mostly excreted renally. HDMTX dosages are prescribed as a function of body surface area whereas dose adjustments depending on renal function are not well defined. We develop a population pharmacokinetic model with a physiological description of renal excretion as the basis for clinical tools able to suggest model-informed dosages and support therapeutic monitoring. METHODS: This article presents a minimal physiologically based pharmacokinetic (PBPK) model for HDMTX, which specifically accounts for individual characteristics such as body weight, height, gender, age, hematocrit, and serum creatinine to provide individualized predictions. The model supplies a detailed and mechanistic description of capillary and cellular exchanges between plasma, interstitial fluid, and intracellular fluid compartments, and focuses on an individualized description of renal excretion. RESULTS: The minimal PBPK model is identified and validated with a literature dataset based on Chinese patients suffering from primary central nervous system lymphoma. A comparison with a pharmacokinetic model from the literature suggests that the proposed model provides improved predictions. Remarkably, the model does not present any significant bias in a wide range of degrees of renal function. CONCLUSION: Results show that model predictions can capture the wide intra- and inter-individual variability of HDMTX, and highlight the role played by the individual degree of renal function. The proposed model can be the basis for the development of clinical decision-support systems for individualized dosages and therapeutic monitoring.

Emergencies in parkinsonism: akinetic crisis, life-threatening dyskinesias, and polyneuropathy during L-Dopa gel treatment.

This article reviews literature on three emergencies in Parkinson's disease (PD): Akinetic crisis, severe dyskinesias or life-threatening dyskinesias, and polyneuropathy during duodenal L-Dopa gel infusion treatment. Akinetic crisis is also known as Parkinsonian hyperpyrexia, Neuroleptic-like malignant syndrome, Acute akinesia, and Malignant syndrome in parkinsonism. It appears in 0.3% of PD patients/year, and is characterized in the most severe cases by total akinesia with dysphagia, hyperthermia, dysautonomia, increment of muscle enzymes and alterations of mental status, but it may also appear in less severe forms ("forme frusta"). At difference with the continuum of motor hypokinesias observed in PD it is characterized by transient (in cases with favorable outcome) unresponsiveness to rescue drugs. Life-supporting measures are mandatory in patients affected by this emergency. Severe dyskinesia, or life-threatening dyskinesia, is due to increased dopaminergic stimulation (either by the patient or by the prescriber): when it appears the level of dopaminomimetic stimulation should be reduced. Polyneuropathy during duodenal L-Dopa gel infusion is a recently described complication, attributed to the onset of Guillain-Barré syndromes. However, hemapheresis was not effective in some reported cases, and recent evidence suggests that Vitamin B12 deficiency or direct high-dose chronic L-Dopa toxicity might play a role in its origin.

Bed footboard peroneal and tibial neuropathy. A further unusual type of Saturday night palsy.

An uncommon cause of bilateral tibial and peroneal compression neuropathy is reported. After taking alcohol and drugs, a young heroin-addicted man lay unconscious overnight in supine position, with both legs crossing the wooden board at the end of the bed, the posterior aspect of the flexed knees pressing against its edge. The following day, he had weakness of foot flexion and extension and a sensory loss consistent with a bilateral tibial and peroneal neuropathy. Symptoms resolved rapidly in the left side; in the right side, a conduction block was still demonstrable 3 weeks later.