Tyrosinemia type 1 in pediatric nephrology: Not always straightforward

The main clinical features of tyrosinemia type 1 usually appear in the first months of life, including fever, diarrhea, vomiting, liver involvement, growth failure, and renal proximal tubulopathy with subsequent hypophosphatemic rickets. An early diagnosis is crucial in order to provide specific management and to prevent complications. Here, we report on two cases referred primarily to pediatric nephrologists for the diagnosis of “neonatal tubulopathy” and management of “X-linked hypophosphatemia (XLH),” respectively. Our aim is to emphasize that (1) even a mixed tubulopathy can reveal tyrosinemia, and (2) tyrosinemia is a classic differential diagnosis of XLH that should not be forgotten, especially in the era of the anti-FGF23 burosumab.     

Malleostapedotomy for otosclerosis,our experience of nitinol piston on twelve patients

ObjectiveMalleostapedotomy allows to completely by-pass the incus in otosclerosis surgery. Recently its use has been rivaled by hydroxyapatite cement for cases of mild and moderate necrosis of the incus. However, it remains gold standard for cases of extensive necrosis, incus dislocation, or epitympanic fixation. Modern heat-crimping pistons make surgery easier and safer. This study focuses on our experience with this technique.MethodsRetrospective analysis of patient’s files and pre- and post-operative audiograms, for cases of surgically treated otosclerosis with malleostapedotomy.ResultsTwelve patients underwent malleostapedotomy for otosclerosis between 2011 and 2019. Amongst them there were 10 revision surgeries and 2 primary cases. 75% had incus long-process necrosis, 17% had epitympanic fixation and one had a history of incus transposition. Nine patients (75%) had closure of air-bone gap (ABG) of <10 dB (p < 0.001) and 11 (92%) had a threshold of 20 dB (p < 0.001). Mean pre-operative ABG was 31 dB (15 dB–55 dB), and mean post-operative ABG was 7 dB (0 dB–21 dB; p < 0.001). There was no sensorineural hearing loss nor any other post-operative complication.ConclusionsMalleostapedotomy is a safe and reliable technique, allowing an ABG closure comparable to conventional incus to vestibule prosthesis. It remains the preferred technique whenever the incus cannot be used.     

Rapid identification of atypical variant of plasma butyrylcholinesterase by PCR.

Human butyrylcholinesterase is the enzyme responsible of mivacurium and succinylcholine metabolism, which may be significantly impaired when mutation Asp70Gly is found in patients. We describe a simple PCR method for the detection of this variant. Thirteen out of sixteen patients tested after prolonged apnea were positive for the presence of this mutation (50.0% homozygotes and 31.3% heterozygotes), suggesting that this test contributes to the explanation of some clinical events and to their prevention in relatives of these patients.     

Effects of Intermittent Femoral Nerve Injections of Bupivacaine, Levobupivacaine, and Ropivacaine on Mitochondrial Energy Metabolism and Intracellular Calcium Homeostasis in Rat Psoas Muscle

Background: Long-acting local anesthetics cause muscle damage. Moreover, long-acting local anesthetics act as uncoupler of oxidative phosphorylation in isolated mitochondria and enhance sarcoplasmic reticulum Ca2+ release. The aim of the study was to evaluate effects of perineural injections of local anesthetics on mitochondrial energetic metabolism and intracellular calcium homeostasis in vivo.

Methods: Femoral nerve block catheters were inserted in adult male Wistar rats. Rats were randomized and received seven injections (1 ml/kg) of bupivacaine, levobupivacaine, ropivacaine, or isotonic saline at 8-h intervals. Rats were killed 8 h after the last injection. Psoas muscle was quickly dissected from next to the femoral nerve. Local anesthetic concentrations in muscle were determined. Oxidative capacity was measured in saponin-skinned fibers. Oxygen consumption rates were measured, and mitochondrial adenosine triphosphate synthesis rate was determined. Enzymatic activities of mitochondrial respiratory chain complexes were evaluated. Local calcium release events (calcium sparks) were analyzed as well as sarcoplasmic reticulum calcium content in saponin-skinned fibers.

Results: Eight hours after the last injection, psoas muscle concentration of local anesthetics was less than 0.3 [mu]g/g tissue. Adenosine triphosphate synthesis and adenosine triphosphate-to-oxygen ratio were significantly decreased in the muscle of rats treated with local anesthetics. A global decrease (around 50%) in all of the enzyme activities of the respiratory chain was observed. Levobupivacaine increased the amplitude and frequency of the calcium sparks, whereas lower sarcoplasmic reticulum calcium content was shown.