Adenosine kinase (ADK) deficiency (OMIM [online mendelian inheritance in man]: 614300) is an autosomal recessive disorder of adenosine and methionine metabolism, with a unique clinical phenotype, mainly involving the central nervous system and dysmorphic features. Patients usually present early in life with sepsis-like symptoms, respiratory difficulties, and neonatal jaundice. Subsequently, patients demonstrate hypotonia and global developmental delay. Biochemically, methionine is elevated with normal homocysteine levels and the diagnosis is confirmed through molecular analysis of the ADK gene. There is no curative treatment; however, a methionine-restricted diet has been tried with variable outcomes. Herein, we report a 4-year-old Saudi female with global developmental delay, hypotonia, and dysmorphic features. Interestingly, she has a tall stature, developmental dysplasia of the hip, optic nerve gliosis, and tigroid fundus. We found a mutation not reported previously and we compared the current case with previously reported cases. We alert clinicians to consider ADK deficiency in any neonate presenting with global developmental delay, hypotonia, dysmorphic features, and high methionine levels.

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