The Diagnostic Dilemma of Hypotonia and Elevated CK

Costia SD, Milkowska-Mikiel D, Azevedo A, Martins T, Afonso I, Soares AR and Martins C

Published on: 2025-11-20

Abstract

Introduction: Prader–Willi syndrome (PWS) is a rare genetic disorder caused by abnormal DNA methylation in the 15q11.2–q13 region, leading to hypothalamic dysfunction with neurodevelopmental, endocrine, and metabolic consequences. Prenatal signs may include decreased fetal movements and polyhydramnios. In the neonatal period, hypotonia and feeding difficulties are common, often requiring nutritional support. Early diagnosis enables timely multidisciplinary intervention.

Case Report: A full-term male infant was delivered by cesarean section for breech presentation (Apgar 6/7/8; birth weight 2900 g). Shortly after birth, he developed bradypnea and hypotonia, requiring positive pressure ventilation and NICU admission for hypoglycemia. Physical examination revealed facial dysmorphism, severe hypotonia, poor reactivity, absent Moro reflex, and bilateral cryptorchidism. Laboratory tests showed markedly elevated CK (18,541 U/L), LDH, AST, and ALT, with normal metabolic and thyroid studies. Imaging was unremarkable except for undescended testes in the iliac fossae. Genetic testing confirmed Prader–Willi syndrome due to maternal uniparental disomy of chromosome 15. The newborn required nasal oxygen until day 15, and CK levels progressively normalized. Feeding gradually improved, achieving full oral intake by day 23. He was discharged on day 29 with follow-up in neurology, endocrinology, rehabilitation, surgery, and genetics. At seven months, he continues physiotherapy and speech therapy.

Conclusion: This case illustrates the early neonatal presentation of PWS and highlights the importance of considering genetic testing in infants with unexplained hypotonia, even when laboratory findings suggest alternative diagnoses such as muscular disease.