Response to “MLASA1 is a poly-phenic but not a di-phenic condition”

To the Editor,

Thank you for sharing with us the letter from Dr. Finsterer's letter to the editor expressing some concerns about our recent article “Myopathy, lactic acidosis and sideroblastic anemia 1 (MLASA1): A 25-year follow up” [1,2] in which we reported on the longer term consequences of PUS1-deficiency in two brothers 25 years after their initial report in the literature. In our paper we reported that the symptoms were limited primarily to the muscles and the bone marrow. We also referenced the reports of patients who were more seriously affected by mutations in this same gene and who had the multisystem disease described by Dr. Finsterer. We did not mean to imply that bi-allelic mutations in PUS1 would not result in more extensive disease in other patients.

Our patients were followed by cardiologists, hematologists, neurologists, endocrinologists, bone specialists, ophthalmologists and any other specialist needed to address an acute problem. No other symptoms related to these systems were noted.

The parents are obviously carriers since they are consanguineous and a mating between their siblings also resulted in two affected offspring. We did not mention that all four parents are free of symptoms related to this condition but do suffer from some infirmities of age.