[Late onset 3-HMG-CoA lyase deficiency: a rare but treatable disorder]. / Déficit en 3-HMG-CoA lyase à révélation tardive : savoir reconnaître une maladie rare mais traitable.

3-Hydroxy-3-methylglutaric aciduria is a rare autosomal recessive genetic disorder due to a deficiency of the 3-hydroxy-3-methylglutarylCoA lyase (HMG-CoA lyase), a mitochondrial enzyme involved in ketogenesis and in the final step of l-leucine catabolism. HMG-CoA lyase deficiency can lead, in particular circumstances, such as fever, prolonged fasting or digestive disorders, to brutal and severe hypoglycemia with metabolic acidosis and sometimes fatal coma. We report on a new case of 3-hydroxy-3-methylglutaric aciduria particular by its late onset in a 3-year-old patient. Molecular investigation identified two new sequence modifications in the HMGCL gene: c.494G>A (p.Arg165Gln) and c.820G>A (p.Gly274Arg). We remind about this case report that the therapeutical is mainly preventive and allows a very good prognosis for this disease. Long-term treatment consists in limited fasting time, continuous low protein diet and l-carnitine supplementation. Preventive measures are essential: prevention of fasting and emergency treatment during intercurrent infections.

[A cause of intracerebral calcifications that should be known: pseudohypoparathyroidism Ib]. / Une cause de calcifications intracérébrales à connaître: la pseudohypoparathyroïdie de type Ib.

In children, pseudohypoparathyroidism (PHP) is a rare but classical cause of basal ganglia calcifications. It is caused by resistance to parathormone (PTH). Hypocalcemia, which may be symptomatic, is its main feature. We report the case of a 13-year-old boy, affected by type Ib PHP revealed by hypocalcemia and seizures, with basal ganglia calcifications on the CT scan. We describe the characteristics of the 2 main types of PHP and emphasize the search for this disease when basal ganglia calcifications are discovered, even fortuitously, on a cerebral CT scan.

Characterization of Silylated Silicas by Inverse Gas Chromatography: Modelization of the Poly(dimethylsiloxane) Monomer Unit/Surface Interactions Using Poly(dimethylsiloxane) Oligomers as Probes

Inverse gas chromatography (IGC) at infinite dilution was used to characterize the fumed silica surface. The silica was modified by chemical treatment with either dimethyldichlorosilane or trimethylchlorosilane. To observe the silica and poly(dimethylsiloxane) (PDMS) interactions, we used apolar (alkanes) and polar probes (chloroform, benzene, tetrahydrofuran, etc.), but also model molecules of PDMS such as linear and cyclic oligomers of PDMS with two to five monomer units. It is shown that PDMS oligomers are very appropriate to discriminate the silylated silicas.