De-novo ATR-16 syndrome associated with inherited hemoglobin Evanston causing HbH phenotype: a rare occurrence

Abnormality of three α-globin genes, either deletion or point mutation results in symptomatic Hemoglobin H (HbH) phenotype. Most of such cases of α-globin defects are inherited from the parents, de-novo cases are exceedingly rare. Herein, a case of HbH is reported where the proband inherited one α-globin gene with a point mutation (α^Evanston) from the mother. This was associated with large de-novo deletion of chromosome 16p13.3 resulting in α-thalassemia and mental retardation (ATR-16) syndrome. This deletion also encompassed two α-globin genes from chromosome 16, eventually leading to --/αα^Evanston genotype, explaining the clinical presentation of the proband. The challenges in screening of such cases and confirming the molecular diagnosis along with the mode of inheritance has been discussed.