Hemoglobin H-constant spring in North America: an alpha thalassemia with frequent complications.

Hemoglobin H-constant spring (Hb H-CS), the most common nondeletional alpha thalassemia in Asia is increasingly recognized in North America due to shifts in immigration patterns. In California, alpha (α)-thalassemia syndromes are the second most frequent finding among newborns screened for hemoglobinopathies with a two-fold increase compared to a decade earlier [1,2]. Though known to have a more severe anemia than Hb H disease, the other clinical findings of Hb H-CS are not well described. Moreover, beneficial therapies that have become available in the last decade are often not applied to their care. This analysis of 46 patients enrolled in the Thalassemia Clinical Research Network (TCRN) age 13+/− 10 years old, with Hb H-CS revealed moderate anemia (mean 8.7 ± 1.5 g/dl), regular transfusion therapy in 24% of patients, and splenomegaly or prior splenectomy in one-third of them. Serum transferin receptor (sTfr), was elevated; (44.4 ± 18 mcg/ml normal range 2.9–8.3 mcg/ml), reflecting ineffective erythropoiesis, which in turn leads to high iron absorption and increased ferritin levels in younger (median = 187 ng/ml) and older (median = 465 ng/ml) nontransfused patients. These findings along with moderate growth delay and low bone mass were more prevalent in Hb H-CS patients compared to deletional Hb H disease. Our results highlight the required monitoring of the extent of anemia, growth, splenomegaly, iron overload, gallstones, bone density and assessment of need for transfusions and specific treatments for disease complications.