Long Term Follow up of a Child with a Rare Hemoglobinopathy: Hemoglobin Little Venice

We report the second known case in the world of a rare beta chain variant hemoglobinopathy Hemoglobin Little Venice [β42 Phe→Cys, HBB:c.128T>G] originally found in 2009 in a 7 month-old Asian Indian female with severe chronic hemolytic anemia during infancy who is now 15 years of age. Her newborn hemoglobinopathy screen showed FA. She presented with jaundice at 1 month of age with a bilirubin of 15 mg/dL initially attributed to breast milk and was managed with supportive care. Hemoglobin electrophoresis with confirmatory DNA sequencing was performed by Mayo Clinic laboratories at 7 months of age to establish the diagnosis. At that time hemoglobin was 5.6 g/dL and bilirubin was 6.9 mg/dL. Hemoglobin electrophoresis showed Hb A 71.6%, Hb A₂ 2.5%, Hb F 24.5% and Hb variant 1.4%. Stability studies were abnormal. The testing revealed a previously undescribed beta 42 mutation of TTT>TGT (Phe>Cys). Our patient has been receiving blood transfusions every four weeks leading to iron overload at 5 years of age treated with an iron chelator. Her growth and development have been normal, similar to peers. At age 9, she had cholecystectomy for gallstones. At the age of 11, she had SARS COVID-19 infection that was treated with supportive care and she recovered well. She was noted to have mild thrombocytopenia ranging from 70-110's and had splenectomy at 13 due to increased frequency of blood transfusion and chronic splenomegaly. At 14, she was treated for asymptomatic babesiosis with atovaquone and azithromycin.

At present, she continues to require regular transfusions every 4 weeks due to severe hemolytic anemia and has significant thrombocytosis along with leukocytosis and nucleated red blood cells. She has significant transfusion-associated hemosiderosis and receives double chelation with deferasirox and deferiprone with marked history of noncompliance. Last MRI of Liver T2* in 2023 showed an approximate hepatic iron concentration of greater than 20 mg/g that is significantly elevated and MRI of heart T2*decay time of greater than 20 ms, which indicates low risk of clinically significant myocardial iron deposition. Both parents and two sisters have no evidence of hemolytic anemia and there are no other family members with chronic anemia or history of splenectomies.

The importance of phenylalanine in position 42 was described by Bartram et al in 2012 for the position's role in maintaining the solubility and stability of the β-hemoglobin chain. When replaced with cysteine, it disrupts oxygen delivery to the cells. This rare hemoglobinopathy requires multiple transfusions to treat vaso-occlusive episodes. At present, little is known regarding treatment choices for this rare hemoglobinopathy therefore, we will continue chronic blood transfusions and encourage compliance with iron chelation. A similar variant affecting the same codon, Hb Hammersmith [β42 Phe→Ser, HBB:c.128T>C] has comparatively more data in the literature which may offer some general guidance.

No relevant conflicts of interest to declare.