Case Quiz (November 2021)
a 12- year-old boy who presented with a recent onset of abdominal pain and diarrhea. Other symptoms included anorexia, weight loss, malaise, and easy fatiguability. He also had a 3- year history of polyuria, recurrent episodes of myalgia, and multiple hospital visits with weakness and muscle spasms for which he was treated with i.v. potassium supplements.
In his last hospital visit, his K was 1.7 mmol/l and Na 118 mmol/l. Family history was remarkable for a highly consanguineous family with similar affected sibling. Both the patient and his brother shared an inability to secrete sweat or tears as well as having a dry mouth and dry scaly skin.
Clinical examination revealed an emaciated, boy (weight 23.1 kg, height 137 cm) with low blood pressure (90/50 mm Hg). He had a triangular face, sunken eyes, xerostomia, poor dentition, and ichthyosis of the lower extremities. He was treated with IV fluids and large doses of potassium chloride. His serum sodium improved but remained between 120-130 mmol/l. Fluid intake was restricted while the salt intake was liberalized and oral sodium chloride tablets were prescribed. Spironolactone was also administered. He was discharged home on these medica- tions with a stable outpatient course and no further emergencies.
His current serum creatinine is 0.8 mg/dl, Ca 10.2 mg/dl and P 4.1 mg/dl.Over the next 6 months his serum creatinine progressed to 1.4 mg/dl. For that rapid unexplained decline in renal function, a kidney biopsy was obtained. The biopsy showed mild acute tubular injury, mild mesangial expansion and hypercellularity, mild to moderate interstitial fibrosis and tubular atrophy, and mild arteriosclerosis. Electron micro- scopy showed mild thickening of glomerular basement membrane while immunofluorescence was negative.
A diagnostic test was done
Case Answer (November 2021)
HELIX syndrome is characterized by hypohidrosis, electrolyte imbalance, lacrimal gland dysfunction, ichthyosis, and xerostomia due to claudin-10 (CLDN10) mutations, was recognized in 2017.
The patient presented clinically with a relatively uniform pattern of polyuria, polydipsia, failure to thrive, hypohidrosis, alacrima, ichthyosis, xerostomia, severe hypokalemia, and either high-normal serum magnesium or frank hypermagnesemia. These features are similar to those described in the previous cases and are consistent with the diagnosis of the HELIX syndrome.
The underlying mutation was detected by whole exome sequencing, confirmed by Sanger sequencing and functionally indicated by RT-PCR, electrophysiological studies and immunohistochemical staining of transfected HEK293 and MDCK C7 cells, and skin and kidney biopsy tissues.
