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Herpes zoster is a common presentation in both the community and emergency department; however segmental zoster paresis is a rare complication that can lead to misdiagnosis. We present a case of a 74-year-old Indian gentleman with a background of well controlled diabetes mellitus, hypertension, and ischaemic heart disease who presented with sudden right lower limb weakness. This was preceded by a 5-day history of paraesthesia starting in the right foot and ascending up the right lower limb. On examination, there was a characteristic vesicular rash in the L2/3 region with MRC grading 3/5 in the right hip flexors. The rest of the neurological examination was unremarkable. MRI of the spine did not show any evidence of spinal disease. The patient was initiated on IV acyclovir with improvement of the lower limb weakness to MRC grading 5/5 as the vesicles improved. This is an interesting case as it highlights a rare presentation of zoster: segmental motor paresis that recovered fully with resolution of the rash. It shows the importance of recognizing motor neuropathy as a complication of shingles as it has a very good prognosis with most patients regaining full motor function of the affected limb with treatment.

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive disorder known to be caused by mutations in at least 19 BBS genes. We report the genetic analysis of a patient with indisputable features of BBS including cardinal features such as postaxial polydactyly, retinitis pigmentosa, obesity, and kidney failure. Taking advantage of next-generation sequencing technology, we applied whole exome sequencing (WES) with Sanger direct sequencing to the proband and her unaffected mother. A pair of heterozygous nonsense mutations in BBS2 gene was identified in the proband, one being novel and the other recurrent. The novel mutation, p.Y644X, resides in exon 16 and was also found in the heterozygous state in the mother. This mutation is not currently found in the dsSNP and 1000 Genome SNP databases and is predicted to be disease causing by in silico analysis. This study highlights the potential for a rapid and precise detection of disease causing gene using WES in genetically heterogeneous disorders such as BBS.

read with interest the observational study by Peters et al. that found reduced minor and major complications after kidney biopsy among patients with serum creatinine ≥150 μmol/L. 1 The authors noted absence of negative sideeffects in their study but acknowledged that electrolyte derangements were not specifically examined. Based on a historical study of 269 transplant allograft biopsies where all received pre-biopsy desmopressin and none had symptomatic hyponatremia, 2 the authors opined that hyponatremia after a single dose of desmopressin was uncommon. However, the low incidence of desmopressin-induced hyponatremia in that study may be due to patients being administered only four 'units' of desmopressin before biopsy. 2 This dose appears much lower compared to the recommended dose of 0.3 μg/kg body weight administered subcutaneously or intravenously. 3,4 Nevertheless, we agree that there are little data on the prevalence of desmopressin-induced hyponatremia after kidney biopsies. Desmopressin is usually administered to individuals with impaired renal function to reduce uremic bleed, but these patients may be at increased risk of developing desmopressin-induced hyponatremia due to prolonged desmopressin half-life in renal dysfunction. In a recent retrospective cohort study of 423 native and allograft kidney biopsies with pre-biopsy serum creatinine ≥150 μmol/L and post-biopsy electrolytes checked based on clinical indications, severe hyponatremia with serum sodium <125 μmol/L occurred after 30 biopsies (7%) at median 2 (1, 4) days after kidney biopsy (abstract presented at the 55th ERA-EDTA Congress, Copenhagen 2018). Logistic regression taking into account age, biochemistry (pre-biopsy serum sodium, urea, estimated glomerular filtration rate, proteinuria) and medications (diuretic, desmopressin dose) found that higher desmopressin dose was independently associated with severe hyponatremia after kidney biopsy [adjusted OR 1.43 (95% CI 1.03, 1.98), P = 0.03].Since desmopressin-induced hyponatremia may be an under-recognized complication of kidney biopsy and associated with significant morbidity, 5 further studies will be required to identify at-risk individuals and determine if post-biopsy biochemistry surveillance is warranted among susceptible patients administered desmopressin to reduce bleeding complications.

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