The authors declare no conﬂict of interest.
M.K., T.O., T.M. and H.S. treated the patient; T.M. reviewed
the manuscript and supervised the whole study process. All
authors read and approved the ﬁnal manuscript.
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Urinary aquaporin-2 as a possible objective biomarker of nocturnal
and Akihiro Yachie
Department of Pediatrics, Kanazawa Medical Center and
Department of Pediatrics, Graduate School of Medical Sciences,
Kanazawa University, Kanazawa, Japan
Key words aquaporin-2, nocturnal enuresis, nocturnal polyuria, urine.
Nocturnal enuresis (NE) is the involuntary voiding of urine
during sleep in the absence of physical disease in children
above the age of 5 years. The major causes of NE are uri-
nary bladder dysfunction and nocturnal polyuria (NP). In
NP, reduction in the nocturnal level of arginine vasopressin
(AVP) leads to a high urine output at night. Desmopressin
acetate (DDAVP) is commonly used to treat NP, but not
all patients respond to DDAVP. Therefore, a new objective
biomarker to reﬂect AVP secretion during sleep is war-
ranted, to select patients with NE for treatment with
Fig. 1 Clinical course. (1) Prednisolone (PSL) 2 mg/kg/day (43 days), then 1 mg/kg/day followed by gradual cessation; (2) methylpred-
nisolone (mPSL) 30 mg/kg/day, 3 days; (3) dexamethasone (DEX) 24 mg/m
/day, 4 days; (4) cyclosporin (CyA) 2–8 mg/kg/day (trough
level, 200–400 ng/mL); (5) platelet transfusion 10 units, three times; (6) PSL 1 mg/kg/day followed by gradual cessation; (7) eltrom-
bopag, initial dose 12.5 mg/day, increased gradually to 37.5 mg/day. IVIG, i.v. immunoglobulin; Plt, platelets.
Correspondence: Masaki Shimizu, MD PhD, Department of Pedi-
atrics, Graduate School of Medical Sciences, Kanazawa University,
13-1 Takaramachi, Kanazawa 920-8641, Japan.
Received 11 August 2017; revised 1 October 2017; accepted 20
192 Y Tasaki et al.
© 2018 Japan Pediatric Society