Urinary stone and infection does not always mean a ‘chicken and egg dilemma’: Answers

Abstract

1. What is your most likely diagnosis? Familial hypomagnesemia with hypercalciuria and nephrocalcinosis. 2. Which laboratory tests do you need for definitive diagnosis? In case of urinary stones and medullary nephrocalcinosis (NC), blood and urine chemistry, blood gas analysis, quantification of lithogenic and inhibitory substances such as oxalate, citrate, magnesium (FeMg), urine electrolytes and thyroid functions tests (for NC); vitamin D levels; PTH; and urine amino acid profile must be checked for diagnosis. Identifying specific crystals such as hexagonal cystine crystals or round, brown 2,8dihydroxyadenine (DHA) crystals may be clues for diagnosis [1, 2]. If diagnosis is uncertain, whole exome sequencing (WES) can give definitive diagnosis [3]. In our patient, presumptive diagnosis of FHHNC was confirmed by genetic analysis in addition to clinical and laboratory features. Homozygous CLDN16 (NM_006580) gene variation (c.623A>G/p.Tyr208Cys) was detected by clinical exome sequencing using the next-generation sequencing platform. 3. How would you manage this patient? Adequate fluid intake, oral magnesium salts, salt restriction to reduce calcium excretion and use of thiazide diuretics to prevent the progression of nephrocalcinosis and stone formation.