Why Do S-HPFH Patients Need Routine Spleen Monitoring?

If you have Hereditary Persistence of Fetal Hemoglobin-Sickle Cell Disease syndrome (S-HPFH), your doctor will periodically check your spleen. You need these check-ups because your spleen is still alive and functioning, which leaves it vulnerable to becoming enlarged or trapping blood ^[1][2]. Even though S-HPFH is generally a mild condition, routine monitoring establishes your “baseline” spleen size, and knowing what is normal for you helps your care team recognize if something goes wrong ^[3][4].

What Does the Spleen Do?

Your spleen is an organ located in the upper left part of your abdomen. It acts as a filter for your blood. It recycles old or damaged red blood cells and stores white blood cells and platelets to help fight infections. For the spleen to do its job, blood must flow smoothly through its tiny vessels.

Classic Sickle Cell vs. S-HPFH

In classic sickle cell disease (HbSS), red blood cells frequently become stiff and sickle-shaped. These misshapen cells get stuck in the small blood vessels of the spleen, blocking blood flow ^[5][6]. Over time, these repeated blockages cause tissue damage, leading the spleen to shrink and stop working early in childhood—a process called autosplenectomy ^[5][6].

S-HPFH is different. Because your body continues to produce high levels of fetal hemoglobin (HbF), your red blood cells are protected from sickling ^[7][8]. The high HbF levels keep the red blood cells round and flexible, which prevents the severe complications seen in classic sickle cell disease ^[7][8]. As a result, your spleen does not suffer the same repeated damage and remains functional ^[7][8].

The Risk of Splenomegaly and Splenic Sequestration

While having a functional spleen is a good thing for fighting infections, it also means your spleen can experience complications later in life that classic sickle cell patients do not face as adults ^[1].

Because your spleen is still active, you can develop splenomegaly, which is an enlarged spleen ^[1]. In some cases, S-HPFH patients can also experience an acute splenic sequestration crisis ^[2][5]. This happens when a large amount of blood suddenly becomes trapped (sequestered) inside the spleen ^[2][5]. This causes the spleen to swell rapidly and leads to a dangerous drop in your blood count (anemia) ^[2][5].

A splenic sequestration crisis is a rapid, potentially life-threatening emergency that can happen suddenly between your routine doctor visits ^[2][5]. You should seek immediate emergency medical care if you experience any of these warning signs:

• Sudden, severe pain or fullness in the upper left side of your abdomen
• Extreme fatigue, weakness, or dizziness
• Unusually pale skin, lips, or nail beds
• A rapid heartbeat or feeling out of breath

Why We Monitor

Your hematologist will perform routine physical exams or imaging to monitor your spleen’s size and function, typically during your regular clinic visits ^[3][4]. Routine monitoring cannot prevent a sudden crisis, but by knowing your spleen’s normal “baseline” size, your care team can easily spot if it starts to enlarge over time or during an illness ^[3][4]. This scheduled monitoring, combined with your awareness of the emergency warning signs, ensures that you and your doctors are prepared to act quickly if your spleen traps blood or becomes overactive ^[3][4].