[Beyond premature apnea pauses: congenital myotonic dystrophy type 1].

Congenital myotonic dystrophy type 1 (DM1) is a rare entity that can pose a diagnostic challenge, especially if other processes such as prematurity coexist.

Objective: to describe the typical presentation of congenital DM1 and thus increase diagnostic suspicion.

Clinical case: A 29-week preterm female newborn who required non-invasive mechanical ventilation until 41 weeks postmenstrual age; she presented with apnea requiring manual ventilation with a self-inflating bag and cardiac massage. Initially, it was attributed to prematurity, but on physical examination, hypotonia, hyporeflexia, bilateral Achilles tendon retraction, facial diplegia, and weak sucking were confirmed. These characteristics, together with the respiratory compromise, suggested a possible congenital neuromuscular disease. The patient's history included infertility in the mother and polyhydramnios during gestation. The examination of the mother showed clinical myotonia, later confirmed by electromyogram, which suggested congenital myotonic dystrophy. This was confirmed genetically, finding 2000 CTG copies in the newborn and 833 in her mother.

Conclusions: Apneas and respiratory compromise in a hypotonic and weak newborn are a frequent manifestation of this disease. The presence of myotonia in the mother of a newborn with suspected neuromuscular disease should lead us to think of congenital DM1. This case highlights the importance of an exhaustive anamnesis and physical examination of the patient and her mother as key elements in the etiological diagnostic orientation.