[Discordant Down syndrome risk calculation with low maternal serum markers: About five cases of digynic triploidies]. / Risque de trisomie 21 discordant en cas de marqueurs sériques très bas : à propos de cinq cas de triploïdie digynique.

OBJECTIVE: We compare the risk of Down syndrome among five patients carrying a foetus with digynic triploidy and suggest a course of action for these particular serological profiles. METHODS: The concentrations of the different markers used are transformed into multiples of the median by using each of the three software types present on the French market which then determine the risk of Down syndrome. RESULTS: For comparable biochemical and ultrasound profiles, the risk of Down syndrome turns out to be vastly different depending on the type of software employed. The relevance of an immediate diagnostic procedure, of a cell free DNA test or of a basic ultrasound follow-up then arises, leading to a potentially variable care pathway for the patient. CONCLUSIONS: This study confirms that for this type of biochemical profile, the laboratory's advisory service is fundamental, that a control ultrasound is essential and that an invasive procedure must be used almost invariably due to the extremely substantial risk factors.

Stage conversion of Toxoplasma gondii in mouse brain during infection and immunodepression.

The kinetics and pattern of expression of bradyzoite-specific proteins were studied in mouse brain during infection with Toxoplasma gondii. Parasites found in the brain 6 days after ingestion of cysts were expressing only tachyzoite-specific proteins (anti-SAG1 antibodies being used as a marker). Bradyzoite-specific protein (Pb36) expression was first found after 9 days in vacuoles containing mixed parasites simultaneously expressing SAG1 and Pb36 or cysts containing parasites expressing only the bradyzoite marker. Reactivation of toxoplasmosis was studied in mouse brain using corticosteroids for immunosuppression. Parasites expressing SAG1 were first found 6 days after the beginning of treatment, but a very heterogeneous pattern was found throughout the study. We simultaneously found vacuoles containing parasites expressing only SAG1 or containing intermediate stages or cysts containing parasites expressing only bradyzoite proteins. A striking observation was the multiplication of cysts in foci, suggesting that the immune suppression triggered the release of parasites from preexisting cysts but that the factors inducing bradyzoite development remained fully effective in driving parasites into this pathway.