Revealing Two New Features of a Rare Variant of Mucolipidosis Type II

A 12-hour-old female infant was referred to our hospital with significant indirect hyperbilirubinemia. She was delivered via cesarean section to a healthy 28-year-old mother at 36 weeks and 6 days gestational age, with a birth weight of 2,245 grams. The physical examination revealed features typical of mucolipidosis Type II. Laboratory tests showed indirect hyperbilirubinemia, thrombocytopenia, and elevated alkaline phosphatase levels. Osteopenia and dysostosis multiplex were observed on the radiographs. Enzyme and gene analysis confirmed the diagnosis: the activity of the N-acetylglucosamine-1-phosphotransferase (GlcNAc-PTase) enzyme was absent, and the baby's GNPTAB gene was homozygous for the c.3503_3504del variant. Fewer than 50 instances of this variant have been documented. We present this rare case and reveal 2 new characteristics of the condition: peripheral heterochromia of the iris and vacuoles in the nucleus of the polymorphonuclear leukocytes.