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Abstract Nail–patella syndrome (NPS) is a hereditary disease caused by pathogenic variants in LMX1B and characterized by nail, limb, and renal symptoms. This study revealed a likely pathogenic LMX1B variant, NM_002316.4: c.723_726delinsC (p.Ser242del), in Japanese twins with clubfoot. The patients’ mother, who shared this variant, developed proteinuria after delivery. p.Ser242del is located in the homeodomain of the protein, in which variants that cause renal disease tend to cluster. Our findings highlight p.Ser242del as a likely pathogenic variant, expanding our knowledge of NPS.

Vitamin K deficiency bleeding (VKDB) in neonates is a significant disorder that causes skin, gastrointestinal, and intracranial hemorrhaging. Early-onset VKDB occurs within 24 hours of birth, and its prognosis is poor due to severe hemorrhage. The causes of early-onset VKDB include maternal intake of warfarin and anticoagulants, and maternal vitamin K deficiency. We report the case of a neonate with early-onset VKDB born to a mother with Crohn's disease. The neonate developed severe cerebellar hemorrhage on the day of birth and subsequent noncommunicating hydrocephalus requiring a ventriculoperitoneal shunt. The mother had a 14-year history of Crohn's disease and short bowel owing to intestinal resection. She was in complete remission during pregnancy according to the Crohn's Disease Activity Index. Endoscopic examination performed shortly before pregnancy revealed inflammatory findings in the residual small intestine. Her blood tests at delivery showed an elevated prothrombin induced by vitamin K deficiency or antagonist II (PIVKA-II) level of 26,900 mAU/mL. A definitive protocol to prevent early-onset VKDB in mothers with Crohn's disease complicated by a short bowel is lacking. Administering vitamin K to mothers with elevated PIVKA-II levels before delivery may help prevent early-onset VKDB.