[Therapeutic Plasma Exchange in a Patient with Chronic Hemodialysis and a New Diagnosis of Myasthenia Gravis]

Case ReportC.S.T. (♂, 71 years old) is a patient with multiple and severe comorbidities, undergoing thrice-weekly chronic hemodialysis since 2008 due to the progression of post-lithiasic uropathy. Over the past 2 months, the patient had been experiencing progressive ptosis of the eyelids, muscle weakness, and ultimately dysphagia and dysarthria that emerged in the last few days. Urgently admitted to the Neurology department, electromyography (EMG) was performed, leading to a diagnosis of predominant cranial myasthenia gravis (with borderline anti-acetylcholine receptor antibody serology). Prompt treatment with pyridostigmine and steroids was initiated. Considering the high risk of acute myasthenic decompensation, therapeutic plasma exchange (TPE) with centrifugation technique was promptly undertaken after femoral CVC placement. TPE sessions were alternated with hemodialysis. The patient's condition complicated after the third TPE session, with septic shock caused by Methicillin-Sensitive Staphylococcus Aureus (MSSA). The patient was transferred to the Intensive Care Unit (ICU). Due to hemodynamic instability, continuous veno-venous hemodiafiltration (CVVHDF) with citrate anticoagulation was administered for 72 hours. After resolving the septic condition, intermittent treatment with Acetate-Free Biofiltration (AFB) technique was resumed. The patient completed the remaining three TPE sessions and, once the acute condition was resolved, was transferred back to Neurology. Here, the patient continued the treatment and underwent a rehabilitation program, showing significant motor and functional recovery until discharge. Conclusions. The multidisciplinary interaction among Nephrologists, Neurologists, Anesthesiologists, and experts from the Immunohematology and Transfusion Medicine Service enabled the management and treatment of a rare condition (MG) in a high-risk chronic hemodialysis patient.

[New Mutation of CYP24A1 in a Case of Idiopathic Infantile Hypercalcemia Diagnosed in Adulthood]

Mutations in the 24-hydroxylase gene CYP24A1 have been recognized as causes of childhood idiopathic hypercalcemia (IIH), a rare disease (incidence <1:1,000,000 live births) characterized by increased vitamin D sensitivity, with symptomatic severe hypercalcemia. IIH was first described in Great Britain two years after the start of a program of vitamin D supplementation in milk for the prevention of rickets, manifesting in about 200 children with severe hypercalcemia, dehydration, growth failure, weight loss, muscle hypotonia, and nephrocalcinosis. The association between the epidemic occurrence of IIH and vitamin D administration was quickly attributed to intrinsic hypersensitivity to vitamin D, and the pathogenic mechanism was recognized in the inactivation of Cytochrome P450 family 24 subfamily A member 1 (CYP24A1), which was identified as the molecular basis of the pathology. The phenotypic spectrum of CYP24A1 mutation can be variable, manifesting predominantly with childhood onset and severe symptomatology (severe hypercalcemia, growth retardation, lethargy, muscle hypotonia, dehydration), but also with juvenile-adult onset forms with nephrolithiasis, nephrocalcinosis, and alterations in phosphocalcium homeostasis. We describe the case of a patient in whom the diagnosis of IIH was made in adulthood, presenting with finding of nephrocalcinosis in childhood, and with subsequent onset of severe hypercalcemia with hypercalciuria, hypoparathyroidism, hypervitaminosis D, and recurrent renal lithiasis. Genetic investigation revealed the presence in homozygosity of the c_428_430delAAG_p.Glu143del variant in the CYP24A1 gene with autosomal recessive transmission, a mutation not reported in the literature.