Massive Splenomegaly in an Adult With a Hemoglobin Fractionation Pattern Suggestive of Hereditary Persistence of Fetal Hemoglobin: A Case Report

Hereditary persistence of fetal hemoglobin (HPFH) is an inherited hemoglobin disorder characterized by continued fetal hemoglobin (HbF) production after infancy and is generally associated with a clinically benign phenotype.Significant splenic enlargement is unusual and should prompt evaluation for other hematological, infectious, vascular, and hepatic causes.We report a 42-year-old man who presented with left-sided abdominal pain and marked splenomegaly, with the spleen palpable approximately 10 cm below the left costal margin.His hemoglobin remained relatively preserved, ranging from 10.9 to 13.6 g/dL, with normal leukocyte counts and intermittent mild thrombocytopenia.The reticulocyte production index was 0.2%, and the overall evaluation did not support active hemolysis.Screening for autoimmune disease, viral infections, and common infectious causes was negative.Abdominal ultrasonography and contrast-enhanced computed tomography demonstrated massive splenomegaly, splenic vein dilatation, and secondary leftsided hydronephrosis from extrinsic compression, while portal venous Doppler showed no evidence of portal hypertension.Hemoglobin analysis by high-performance liquid chromatography revealed complete predominance of HbF (100%) with no detectable adult hemoglobin (HbA) or adult hemoglobin A2 (HbA2), a pattern consistent with an HPFH phenotype.Bone marrow biopsy demonstrated preserved trilineage hematopoiesis without evidence of a primary hematological malignancy.The patient was managed conservatively with supportive treatment and was advised hematology follow-up and family screening.This case is notable for the coexistence of massive splenomegaly and an HPFH phenotype in an adult with relatively preserved hemoglobin and no convincing evidence of hemolysis.It highlights the importance of hemoglobin fractionation in the evaluation of unexplained splenomegaly and emphasizes that an unusual hemoglobin profile should be interpreted alongside the clinical phenotype and appropriate exclusion of alternative causes.Recognition of this benign hemoglobin phenotype may help avoid unnecessary invasive interventions when other causes of splenomegaly have been adequately excluded.