Thin Ribs on Chest X-Ray—a Sign Pointing the Way to the Diagnosis of Congenital Myotonic Dystrophy

Delivery of a full-term eutrophic neonate took place in the setting of prenatal polyhydramnios in a subjectively symptom-free primigravida. Due to pronounced respiratory distress, the neonate needed to be intubated and mechanically ventilated on the intensive care unit. Mechanical ventilation was required for 6 days. In addition, the infant exhibited pronounced muscular hypotonia (“floppy infant”) and very poor feeding, with prolonged weaning from tube feeding over 6 weeks. Furthermore, a chest radiograph showed thin gracile ribs (Figure), prompting suspicion of a (neuro-)muscular disease. Clinical examination of the child’s mother, who exhibited abnormal facies, revealed grip myotonia during handshake. This strengthened the suspicion of congenital myotonic dystrophy type 1 (DM1) in the newborn. Autosomal dominant congenital DM1 is due to a CTG repeat expansion of the DMPK (dystrophia myotonica protein kinase) gene on chromosome 19q13.32. Molecular genetic testing of the infant revealed pathological expansion (>> 1000 CTG units), thereby confirming the suspected diagnosis. In view of the syndromic nature of the disease, the infant was referred to a social pediatric center.

Figure

Bell-shaped thorax and gracile ribs (arrows) on AP chest radiograph

Jana Hiekel, Dr. med. Maxi Kaufmann, PD Dr. med. Jürgen Dinger, Fachbereich Neonatologie, Klinik und Poliklinik für Kinder und Jugendmedizin, Medizinische Fakultät Carl Gustav Carus, TU Dresden; [e-mail]

Conflict of interest statement: The authors state that no conflict of interest exists.

Translated from the original German by Christine Rye.

Cite this as: Hiekel J, Kaufmann M, Dinger J: Thin ribs on chest X-ray—a sign pointing the way to the diagnosis of congenital myotonic dystrophy. Dtsch Arztebl Int 2022; 119: 305. DOI: 10.3238/arztebl.m2022.0029