Abstract: 【Abstract】 To report 2 cases of Iso-Kikuchi syndrome, both of which were congenital. Case 1, a 7-month-old female infant, visited the hospital due to abnormalities in the nail plate of the left index finger for 7 months; case 2, a 3-year-old male child, also visited the hospital due to abnormalities in the nail plate of the left index finger for 3 years. The 2 patients both presented with 2 tiny, independent nail plates on both sides of the nail bed of the left index finger, instead of normal nail plates. Based on their clinical features, the 2 patients were diagnosed with Iso-Kikuchi syndrome （congenital onychodysplasia of the index finger）. The mother of case 1 had a history of progesterone use to prevent miscarriage during pregnancy, the mothers of the two patients both suffered from hypothyroidism and continued to receive thyroid hormone replacement therapy during pregnancy, and the mother of case 2 had a history of gestational diabetes. It is still unclear whether these comorbidities and drugs are directly related to the occurrence of Iso-Kikuchi syndrome.

Key words: Congenital onychodysplasia of the index fingers, Iso-Kikuchi syndrome, Clinical manifestations