A 14-year-old male presented to the Emergency Department with signs and symptoms of acute cholestatic hepatitis, including fatigue, jaundice, and abdominal pain. Laboratory testing revealed elevated transaminases and GGT values. The condition was attributed to a rotavirus infection, and the patient was transferred to the Internal Medicine Department for further investigations. His family history was noteworthy: the patient's father was a carrier of an undetermined polycythemia requiring regular phlebotomy since 2000, while the mother was known to have thalassemia trait. The maternal grandmother had an unverified history of hereditary spherocytosis. Magnetic resonance imaging (MRI) revealed an enlarged liver with a craniocaudal length of 20 cm, a gallbladder with non-thickened walls, but with heterogeneous endoluminal signal due to the presence of a 15 mm gallstone, and an enlarged spleen, measuring 19 cm craniocaudally. Hematological and biochemical data are shown in Table 1 and a corresponding peripheral smear in Figure 1. A complete blood count (CBC) revealed erythrocytosis (RBC 8. 44 × 106/μL) with normal hemoglobin (16. 4 g/dL) but increased hematocrit (53. 5%) (Table 1). Red cell indices indicated microcytosis (MCV 63. 4 fL) and hypochromia (MCH 19. 4 pg). Platelet count was reduced (115 × 103/μL). The reticulocyte count was elevated (3. 8%) with a high immature fraction (IRF 20. 9%) and low reticulocyte hemoglobin content (21. 8 pg). Hemoglobin electrophoresis showed increased HbA2 (6. 6%) and HbF (3. 9%), consistent with a hemoglobinopathy. Markers of hemolysis were also evident, including elevated total bilirubin (5. 05 mg/dL), reduced haptoglobin (T]) (rs11549407) and for a G → A mutation at codon 109 (GTG → ATG, Val → Met, HBB: c. 328G>A) (rs33969677) responsible for the synthesis of Hb San Diego, a high-affinity hemoglobin variant. The presence of both mutations was confirmed by amplification refractory mutation system (ARMS-PCR). Large rearrangements in the HBA cluster were examined by MLPA analysis (MLPA P140-C1 HBA probe mix, MRC-Holland, Amsterdam, NL), revealing the presence of an α-globin gene triplication (αααanti3. 7). Furthermore, the morphological appearance of the peripheral blood smear, characterized by the absence of spherocytes and the presence of stomatocytes, prompted us to perform additional molecular investigations for suspected hereditary red blood cell membrane defects. The proband underwent analysis using a custom 124-gene panel targeting hereditary red blood cell defects, as previously described 1, 2. Variant interpretation was conducted according to ACMG/AMP guidelines, integrating data on population frequency, computational predictions, functional studies, and segregation analysis. This evaluation revealed the presence of a heterozygous missense variant, NM₀02250. 3: c. 1018C>A (p. His340Asn; rs76935412, T = 0. 001539) in the KCNN4 gene. This variant has been previously reported as causative of dehydrated hereditary stomatocytosis (DHS) type 2. Segregation analysis in first-degree relatives identified the same variant in the proband's mother. To further support these findings, ektacytometry was carried out on blood samples obtained from the proband, demonstrating a mild left shift of the osmolarity curve compared with healthy controls, as well as mildly decreased deformability (Figure 2). Of note, the ektacytometry curve is typically not altered in most patients carrying KCNN4 mutations, with some mutations, such as V282M, showing a left shift and others, such as R352H, exhibiting normal curves 3. However, in our patient, the co-presence of additional mutations, such as in the HBB gene, accounts for the dehydration of red blood cells. α-globin gene triplication (αααanti3. 7) (inherited from the father), a high-affinity hemoglobin variant (Hb San Diego) (inherited from the father), for a G → A mutation at codon 109 in beta globin gene (GTG → ATG, Val → Met, HBB: c. 328G>A) (rs3396977), β039 mutation (HGVS name HBB: c. 118C>T) (rs11549407) (heterozygous, inherited from the mother), and a KCNN4 pathogenic variant associated with DHS (inherited from the mother). Following the resolution of the infectious episode, the patient was clinically asymptomatic. No cyanosis, pallor, or plethora was observed, although a mild jaundice was present. This case highlights the complexity of hematological disorders inherited through distinct familial lineages, where overlapping features can complicate diagnosis and management 4, 5. Given the diagnostic challenges posed by these conditions, an accurate family history and a thorough understanding of their clinical presentations are essential. Hb San Diego is a rare β-globin variant with increased oxygen affinity, first described in Italy in 2002 6. It leads to impaired oxygen delivery and compensatory erythrocytosis. The clinical phenotype is usually mild or asymptomatic, with persistently elevated hemoglobin and hematocrit in the absence of splenomegaly or major complications. By contrast, α-globin triplication and β-globin codon 39 mutations cause a form of NTDT common in southern Italy 7, characterized by microcytosis, anemia, chronic hemolysis, and ineffective erythropoiesis predisposing to complications such as extramedullary hematopoiesis, gallstones, splenomegaly, and pulmonary hypertension, and thrombosis. Similarly, hereditary stomatocytosis (HS), a rare disorder affecting red blood cell membrane permeability, contributes to chronic hemolysis and splenomegaly, with certain mutations also predisposing patients to venous thromboembolism 3. HS has been increasingly reported in combination with beta-thalassemia carriers 8. To date, the simultaneous presence of all three conditions in a single patient has not yet been documented. The coexistence of these disorders resulted in overlapping and potentially synergistic or opposite effects, contributing to the unique patient's clinical and biochemical presentation. Notably, anemia was absent since the anemia associated with NTDT was counterbalanced by the polycythemia due to high-affinity hemoglobin. The elevated RBC count and HCT, unusual in Hb San Diego, likely reflected the result of the combination of NTDT and high-affinity hemoglobin, as already observed in compound heterozygotes for high-affinity variant and thalassemic gene and may also account for the associated hyperuricemia through increased red cell turnover and purine catabolism 9, 10. Conversely, the marked erythrocytosis likely caused the observed hypoglycemia through increased glucose consumption in vitro 11. Both the particular increase in hemolysis markers and splenomegaly were attributable to the combined effects of HS and NTDT. However, one of the most challenging aspects of this case is the therapeutic management and clinical monitoring. The elevated hematocrit warrants consideration of phlebotomy to prevent complications such as cardiac overload and pulmonary hypertension for which the patient appears predisposed both by increased hematocrit and the underlying hemolytic anemia 12, 13. However, the decision to initiate phlebotomy must weigh the risk of exacerbating anemia and symptoms of hypoxia against the benefits of reducing hyperviscosity-related complications. The possible role of antiplatelet agents also deserves consideration, either as an alternative or adjunct to phlebotomy, in reducing thrombotic risk in this complex setting. Given the elevated hematocrit and the coexistence of thrombosis-prone conditions such as HS and NTDT, low-dose antiplatelet therapy, particularly acetylsalicylic acid, might represent a rational option, though potential bleeding risks must be balanced against the expected reduction in thrombotic risk. Another key aspect of long-term follow-up is the possible tendency toward iron accumulation, due to mechanisms linked to erythroid expansion and altered iron homeostasis in patients with NTDT and HS, where ERFE-induced hepcidin suppression and mutations in PIEZO1 or possibly in KCNN4 may directly alter iron metabolism 14, 15. Surveillance for extramedullary erythropoiesis could be crucial, given the risk of development of paraspinal masses and compressive complications. Furthermore, regular monitoring of the gallbladder, biliary tract, and kidneys by ultrasound is recommended in the setting of chronic hemolysis, which predisposes to gallstone formation, while concomitant hyperuricemia may further increase the risk of renal stones. In conclusion, this case highlights the necessity of a multidisciplinary approach in the management of rare and overlapping hematological disorders. The unique combination of genetic mutations in this patient needs a comprehensive and personalized follow-up plan to optimize long-term outcomes. A multidisciplinary discussion involving experts in hematology, genetics, and internal medicine is highly recommended, and a debate based on expert opinions on the optimal approach to treatment and monitoring would be particularly valuable in guiding clinical decision-making and improving patient care. The authors have nothing to report. Written informed consent was obtained from the patient for the publication of any potentially identifiable data and images. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
Fatigati et al. (Thu,) studied this question.