A 2-year-old girl with merged phenotypes: galactosemia and Coffin–Lowry syndrome

Abstract Objectives Galactosemia is a congenital disorder of carbohydrate metabolism, in which the body is unable to metabolize galactose properly. Coffin–Lowry syndrome (CLS) is characterized by intellectual disability, developmental delay, dysmorphic features, growth retardation, vision and hearing loss, and skeletal changes, which is an X-linked disorder, with males being more severely affected, whereas the clinical findings in females show variability. This case is presented due to the rare concomitance of galactosemia and CLS. Case presentation A 2-year-old female patient, previously diagnosed with galactosemia, who had good dietary adherence was noticed to have developmental delay, dysmorphic features, nephrolithiasis and recurrent pericardial effusions during follow-up. Further research was carried out to diagnose an underlying second disease. Metabolic tests were inconclusive. Clinical exome sequencing (CES) analysis, revealed a heterozygous c.472C>T p. (Arg158Cys) pathogenic variant in RPS6KA3 (OMIM #300075) and CLS (OMIM #303600) was diagnosed. Conclusions This case report is a unique summary of a patient with galactosemia who further was diagnosed with CLS that emphasizes the possibility of co-occurrence of rare diseases and highlights the importance of conducting further investigations in patients with unexplained findings in the context of existing metabolic diseases.