Howell-Jolly bodies appear on blood smears in any condition that removes or impairs the spleen’s filtering function, and in certain disorders where red blood cell development itself goes wrong. The most common trigger by far is surgical removal of the spleen, but the list extends well beyond that: sickle cell disease, celiac disease, lupus, severe infections, bone marrow transplants, and vitamin B12 or folate deficiency can all produce these small nuclear remnants inside circulating red blood cells. Spotting them on a routine blood smear often tells a clinician something important about what is happening inside the body, even before other tests come back.
What Howell-Jolly Bodies Actually Are
When red blood cells mature in the bone marrow, they go through a dramatic final step: they eject their nucleus entirely. This is what makes mature red blood cells unique among human cells. Occasionally, a tiny fragment of nuclear material gets left behind, a dark-staining dot visible under the microscope inside an otherwise normal-looking red blood cell. These leftover bits of DNA are Howell-Jolly bodies, named after the American physiologist William Howell and the French histologist Justin Jolly, who were among the first to describe them in the late 19th and early 20th centuries.1The American Journal of the Medical Sciences. Understanding Howell-Jolly Bodies
In a healthy person with a functioning spleen, these fragments rarely survive in the bloodstream. The spleen acts as a quality-control checkpoint, removing inclusions and defective cells as blood passes through it. When the spleen is absent, damaged, or overwhelmed, Howell-Jolly bodies slip through and show up on a peripheral blood smear. That is why finding them is almost always a signal pointing back to one of two broad categories: something is wrong with the spleen, or something is wrong with the way red blood cells are being made.
After Splenectomy and in Congenital Asplenia
The single most frequent reason Howell-Jolly bodies appear is that the spleen has been surgically removed. People lose their spleens for all sorts of reasons: trauma from a car accident or sports injury, treatment for blood disorders like hereditary spherocytosis or immune thrombocytopenia, or as part of cancer staging procedures. Once the spleen is gone, there is no organ left to pluck those nuclear remnants out of circulating red cells, so Howell-Jolly bodies become a permanent fixture on the blood smear.2PubMed Central. Howell-Jolly bodies on peripheral smear leading to the diagnosis of congenital hyposplenism in a patient with septic shock
Much rarer is congenital asplenia, where a person is born without a spleen or with one that never developed properly. This can go undetected for years or even decades. In fact, some people only discover they have congenital asplenia when they develop a severe infection and a clinician spots Howell-Jolly bodies on their blood work.2PubMed Central. Howell-Jolly bodies on peripheral smear leading to the diagnosis of congenital hyposplenism in a patient with septic shock In these cases, the Howell-Jolly bodies are not just a curiosity; they are the diagnostic clue that leads to the underlying condition being identified in the first place.
Sickle Cell Disease and Other Causes of Functional Hyposplenism
You do not have to lose your spleen entirely for Howell-Jolly bodies to appear. Functional hyposplenism, where the spleen is still physically present but no longer working properly, produces the same result. Sickle cell disease is the textbook example. Repeated episodes of sickling damage the small blood vessels inside the spleen, gradually turning it into a shrunken, scarred organ that can no longer filter blood effectively. This process, sometimes called autosplenectomy, often begins in early childhood. By the time many people with sickle cell disease reach adulthood, their spleen has essentially stopped functioning, and Howell-Jolly bodies are a routine finding on their blood smears.
Other hemolytic anemias can produce the same end result, though less predictably. Any condition that chronically overworks the spleen by forcing it to clear large numbers of damaged red cells can eventually exhaust or damage the organ. Thalassemia major, for instance, can lead to functional hyposplenism even without surgical removal of the spleen.
Celiac Disease and Gastrointestinal Disorders
The connection between gut diseases and spleen function surprises many people, but it is well established. Celiac disease is the gastrointestinal disorder most frequently linked to functional hyposplenism and, consequently, to the appearance of Howell-Jolly bodies.3Digestive Diseases. Hyposplenism and Gastrointestinal Diseases: Significance and Mechanisms The risk scales with how severe and complicated the celiac disease is. In uncomplicated adult celiac patients, roughly one in five shows signs of reduced spleen function. That number climbs steeply when complications are present: about 60% of celiac patients with associated autoimmune diseases and as many as 80% of those with certain rare intestinal lymphomas show functional hyposplenism.3Digestive Diseases. Hyposplenism and Gastrointestinal Diseases: Significance and Mechanisms
Two distinct processes seem to be at work. One is a functional decline in the spleen’s filtering ability, which appears to be reversible with a strict gluten-free diet. The other is actual physical shrinkage of the spleen (splenic atrophy), which does not reverse with dietary changes.3Digestive Diseases. Hyposplenism and Gastrointestinal Diseases: Significance and Mechanisms For celiac patients, this means that finding Howell-Jolly bodies on a blood smear is not just a hematological footnote; it carries real implications for infection risk and may signal more advanced or complicated disease.
Inflammatory bowel disease (particularly ulcerative colitis and Crohn’s disease) and other chronic gastrointestinal conditions have also been associated with hyposplenism, though less commonly than celiac disease. The mechanism is less well understood in these cases, but chronic inflammation and immune dysregulation are thought to play a role.
Autoimmune Diseases
Systemic lupus erythematosus (lupus) is another disease where Howell-Jolly bodies occasionally appear. Hyposplenism shows up in roughly 5% of lupus patients and is thought to result from vasculitis, the inflammation and damage to small blood vessels inside the spleen.4Journal of Osteopathic Medicine. Splenic hypofunction in systemic lupus erythematosus When that vascular damage accumulates, the spleen loses its ability to clear abnormal cells and inclusions, and Howell-Jolly bodies start appearing on the peripheral smear. Clinicians sometimes use the presence of Howell-Jolly bodies as a quick screen for hyposplenism in lupus patients, since the condition carries an increased risk of serious infections.5PubMed Central. Hyposplenism in systemic lupus erythematosus: biological and radiological characteristics and its association with increased risk of infection
Other autoimmune conditions associated with hyposplenism include rheumatoid arthritis, thyroiditis, and sarcoidosis, though the evidence base for these is thinner. The common thread seems to be chronic immune activation that can secondarily damage the spleen over time. Hyposplenism can also occur in people with multiple autoimmune conditions simultaneously, which is not unusual since autoimmune diseases tend to cluster.
Vitamin B12 and Folate Deficiency
Here is where the picture shifts. In most of the conditions above, Howell-Jolly bodies appear because the spleen is not doing its filtering job. But in vitamin B12 or folate deficiency, the spleen may be perfectly healthy. Instead, the problem is in the bone marrow itself. Both B12 and folate are essential for proper DNA synthesis. When either is severely lacking, red blood cell precursors divide abnormally. The nuclear material does not get cleanly expelled, leaving behind more remnants than normal. In marrow samples from patients with these deficiencies, more than 1% of later-stage red cell precursors contain Howell-Jolly bodies, a threshold rarely reached in other conditions.6PubMed Central. The significance of Howell-Jolly bodies and giant metamyelocytes in marrow smears
This distinction matters because the treatment is completely different. A person with Howell-Jolly bodies from B12 deficiency does not need vaccines against encapsulated bacteria or lifelong infection monitoring; they need B12 supplementation. The bodies disappear once the deficiency is corrected and red cell production normalizes.
Myelodysplastic Syndromes and Bone Marrow Disorders
Myelodysplastic syndromes (MDS) are a group of bone marrow cancers where blood cells are produced abnormally. The hallmark of MDS is dysplasia, meaning the cells look and behave abnormally under the microscope. Howell-Jolly bodies can appear in the red cell precursors of MDS patients, and they serve as one of several morphological clues that something is wrong with the marrow’s production line.7Haematologica. Diagnosis of myelodysplastic syndromes: the classic and the novel The underlying defect here involves problems with the final stages of red cell maturation, including faulty nuclear expulsion and chromosome missegregation during the last cell division before the nucleus is ejected.8Scientific Reports. H2AX deficiency is associated with erythroid dysplasia and compromised haematopoietic stem cell function
Other marrow-based conditions where Howell-Jolly bodies have been reported include severe aplastic anemia and certain leukemias. Bone marrow transplant recipients can also develop functional hyposplenism, sometimes presenting with Howell-Jolly bodies well after transplant. In one reported case, recurrent pneumococcal infections in a bone marrow transplant patient were traced back to functional hyposplenism after Howell-Jolly bodies were noticed on a routine blood smear.9PubMed. Pneumococcal sepsis due to functional hyposplenism in a bone marrow transplant patient
HIV and Other Infections
HIV infection adds another dimension. A study examining peripheral blood smears from HIV-positive patients found Howell-Jolly body-like inclusions in about 7% of cases. Interestingly, the patients who had these inclusions tended to have higher CD4 counts (averaging around 546 cells per microliter) compared to those without inclusions (around 247 cells per microliter).10PubMed Central. Prevalence of Howell-Jolly body-like inclusions in HIV patients and their correlation with CD4 counts and HIV RNA viral load This counterintuitive finding (you might expect sicker patients to have more abnormalities) has not been fully explained, and the inclusions seen in HIV may not be identical to classic Howell-Jolly bodies. The relationship between HIV and spleen function is complex, since the virus can affect the spleen both directly and through the secondary infections and immune changes it causes.
Other infectious diseases associated with hyposplenism tend to be chronic or severe. Malaria, for example, can cause massive spleen damage over time, particularly in areas where infection is recurrent. Severe sepsis from any cause can also temporarily impair spleen function.
How Howell-Jolly Bodies Are Detected
The standard way to spot Howell-Jolly bodies is straightforward: a trained lab technician or pathologist examines a blood smear stained with a standard dye under a microscope. They appear as small, round, dark-purple dots sitting inside red blood cells, usually one per cell. The test is cheap, fast, and widely available, which makes it a practical first-line screen for reduced spleen function.11PubMed. Hyposplenism: a comprehensive review. Part I: basic concepts and causes
That said, the blood smear has limitations. It can miss mild hyposplenism because a partially functioning spleen may still clear enough inclusions to keep the count below what the eye can reliably detect. More sensitive methods exist for confirming reduced spleen function:
- Pitted red cell count: A specialized microscopy technique that counts tiny surface pits on red blood cells. Elevated counts indicate the spleen is not properly grooming circulating red cells. This method can detect milder degrees of hyposplenism than a standard smear.
- Spleen scintigraphy: A nuclear medicine scan where a radioactive tracer is injected and imaged to assess how much functioning spleen tissue remains. It can estimate functional splenic volume.
Comparisons between these methods show that Howell-Jolly bodies, pitted red cell counts, and scintigraphy often correlate but do not always agree perfectly, particularly in borderline cases.12PubMed. Hyposplenism: comparison of different methods for determining splenic function For practical purposes, most clinicians rely on the blood smear as a starting point and reserve the more involved tests for situations where the degree of hyposplenism needs to be quantified.
Why Finding Them Matters for Infection Risk
The clinical significance of Howell-Jolly bodies is not about the bodies themselves; they are harmless fragments of DNA floating inside a red cell. The danger is what their presence signals about the spleen. A spleen that cannot clear nuclear remnants from red blood cells is also failing at one of its other critical jobs: trapping and destroying bacteria that have a protective outer capsule. These encapsulated bacteria, particularly Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis, rely on that capsule to evade other parts of the immune system. The spleen is the body’s primary defense against them.
People with hyposplenism or asplenia face a lifelong elevated risk of overwhelming post-splenectomy infection, a fulminant bacterial sepsis that can progress from mild symptoms to death within hours. This risk does not go away over time; if anything, complacency years after a splenectomy may be more dangerous than the immediate postoperative period because patients and physicians can forget about the vulnerability. Vaccination against pneumococcus, meningococcus, and Haemophilus influenzae type b is recommended for anyone known to have absent or diminished splenic function, along with prompt antibiotic treatment at the first sign of fever or infection.
When Howell-Jolly bodies are found unexpectedly in someone who has not had a splenectomy, the finding triggers a diagnostic workup. The clinician needs to figure out why the spleen is underperforming. Is there an undiagnosed autoimmune condition? Celiac disease? A hemoglobinopathy? The answer determines both the treatment and the infection-prevention strategy. In the bone marrow transplant case mentioned earlier, the discovery of Howell-Jolly bodies during a hospitalization for pneumococcal sepsis was what connected the dots between the patient’s recurrent infections and their impaired spleen function.9PubMed. Pneumococcal sepsis due to functional hyposplenism in a bone marrow transplant patient
Conditions Where Howell-Jolly Bodies Are Easily Confused With Something Else
Not every dark dot inside a red blood cell is a Howell-Jolly body. Several other inclusions can look similar under the microscope, and mistaking one for another can lead to the wrong clinical conclusions. Pappenheimer bodies, for instance, are iron-containing granules that also appear as small dots in red cells but stain differently with special iron stains. Basophilic stippling, caused by clumps of ribosomal material, creates a speckled pattern across the entire cell rather than a single discrete dot. Parasites like Plasmodium (the malaria organism) can also produce ring-shaped inclusions inside red cells that an inexperienced observer might initially confuse with nuclear remnants.
The HIV study’s use of the phrase “Howell-Jolly body-like inclusions” rather than simply “Howell-Jolly bodies” hints at this diagnostic uncertainty.10PubMed Central. Prevalence of Howell-Jolly body-like inclusions in HIV patients and their correlation with CD4 counts and HIV RNA viral load In practice, an experienced hematologist or lab technician can usually distinguish genuine Howell-Jolly bodies from look-alikes based on their size (typically 1 to 2 micrometers), their perfectly round shape, their deep purple staining, and their tendency to appear singly rather than in clusters. When there is doubt, additional staining or flow cytometry can help confirm what the inclusion actually is.
Reversible Versus Permanent Causes
One practical question patients and clinicians face is whether the appearance of Howell-Jolly bodies signals a permanent change or something that can be corrected. The answer depends entirely on the underlying cause. After a splenectomy, the bodies are permanent because the organ is gone. In sickle cell autosplenectomy, the damage is typically irreversible as well.
On the other end of the spectrum, Howell-Jolly bodies caused by B12 or folate deficiency resolve once the nutritional deficit is corrected.6PubMed Central. The significance of Howell-Jolly bodies and giant metamyelocytes in marrow smears Celiac disease occupies interesting middle ground: functional hyposplenism can improve with a strict gluten-free diet, but if the spleen has already undergone physical atrophy, that structural damage does not reverse.3Digestive Diseases. Hyposplenism and Gastrointestinal Diseases: Significance and Mechanisms This is why early diagnosis and dietary adherence matter: catching celiac-related hyposplenism before atrophy sets in gives the spleen its best chance of functional recovery.
For autoimmune causes like lupus, treatment of the underlying disease with immunosuppressive therapy may improve spleen function in some patients, though data on this are limited. In bone marrow transplant recipients, spleen function may recover gradually over months to years as the new marrow engrafts and the immune system reconstitutes, but this is unpredictable and not guaranteed.