10 Common Diseases That Cause Secondary Immunodeficiency

Several widespread medical conditions quietly erode the immune system from the inside out, creating what clinicians call secondary immunodeficiency. Unlike inherited immune disorders present from birth, secondary immunodeficiency develops as a consequence of another disease, and it is far more common than most people realize. Malnutrition alone accounts for a huge share of immune suppression worldwide, while conditions as varied as diabetes, chronic kidney disease, and HIV each dismantle different arms of immune defense through distinct mechanisms. Understanding which diseases carry this risk matters because the resulting vulnerability to infections is often treatable once the underlying cause is identified.

HIV Infection

HIV remains the textbook example of disease-driven immunodeficiency. The virus targets and gradually destroys a specific subset of white blood cells, CD4+ T-cells, which coordinate much of the body’s immune response. Over months to years, the progressive loss of these cells leaves a person increasingly unable to fight off infections that a healthy immune system handles with ease. Without treatment, this deterioration eventually leads to AIDS, defined by a critically low CD4+ count and the appearance of opportunistic infections like certain pneumonias, fungal diseases, and unusual cancers.

The good news is that modern antiretroviral therapy can substantially reverse this damage. Suppressing the virus allows the immune system to begin rebuilding. In the first three months of effective treatment, both naive and memory T-cells and B-cells rise in a rapid initial wave, followed by a slower ongoing increase over the months that follow.¹ Although full immune restoration remains incomplete even after a year of treatment, the recovery is sufficient in most cases to protect against the opportunistic infections that define AIDS. This partial reversibility distinguishes HIV-related immunodeficiency from some other causes on this list, where the immune damage is harder to undo.

Type 2 Diabetes

Diabetes does not announce itself as an immune disease, yet people with poorly controlled blood sugar face a measurably higher risk of bacterial and fungal infections. The mechanism centers on what chronically elevated glucose does to immune cells, particularly neutrophils, the first responders that rush to engulf invading bacteria.

When blood sugar stays high, excess glucose gets shunted through an alternative metabolic route called the polyol pathway. This process drains a molecule called NADPH, which neutrophils rely on to produce the reactive oxygen species they use to kill bacteria. With NADPH depleted, these cells lose their killing power and their ability to maintain internal defenses against oxidative damage.² The result is that a diabetic person’s neutrophils may arrive at an infection site but fail to do their job properly. This helps explain why foot infections, urinary tract infections, and surgical wound infections are disproportionately common and severe in people with diabetes.

Chronic Kidney Disease

As kidney function declines, the organs lose their ability to filter waste products from the blood. The resulting buildup of uremic toxins has wide-ranging effects, and immune cells are among the casualties. Research has identified a large number of retained uremic compounds that directly impair the function of various immune cell types.³ Phagocytes become less effective at engulfing pathogens. T-cells respond sluggishly to threats. Vaccine responses tend to be blunted, which is why people on dialysis often need higher or more frequent vaccine doses.

People with advanced kidney disease, especially those on dialysis, are at significantly elevated risk for infections, which rank among the leading causes of hospitalization and death in this population. The immune suppression worsens as kidney function deteriorates, making early management of kidney disease doubly important.

Malnutrition

Globally, malnutrition is considered the most common cause of secondary immunodeficiency.⁴ Severe protein-energy malnutrition, the kind seen in famine conditions and severe wasting illness, hits the immune system especially hard. Children are particularly vulnerable. Studies using thymic ultrasound have shown that severe malnutrition causes critical shrinkage of the thymus, the organ where T-cells mature. The result is a drop in circulating mature T-cells and a rise in immature, nonfunctional ones.⁵

But malnutrition-related immune suppression is not limited to starvation. Deficiencies in specific micronutrients like zinc, iron, vitamin A, and vitamin D can each impair different arms of the immune response. Older adults living with chronic illness are at particular risk for this kind of subtle nutritional immune suppression, even in wealthy countries, because appetite loss, medication side effects, and absorption problems conspire to create deficiency states that fly under the radar.⁶

Hematologic Malignancies

Blood cancers like chronic lymphocytic leukemia, lymphoma, and multiple myeloma are among the most clinically important causes of secondary immunodeficiency. These cancers arise in the very cells that make up the immune system, so the disease process itself disrupts immune function from the start. Low antibody levels, known as hypogammaglobulinemia, are a frequent finding in patients with these cancers, sometimes appearing before any treatment begins.⁷

Treatment compounds the problem. Many chemotherapy regimens and newer targeted therapies further deplete antibody-producing cells or suppress other parts of the immune response. In chronic lymphocytic leukemia specifically, there is ongoing debate about whether immunoglobulin replacement therapy should become standard care, given how prevalent and persistent the antibody deficiency is. For patients with these cancers, infection is not just a side effect of chemotherapy; it is a consequence of the cancer itself.

Liver Cirrhosis

The liver is far more involved in immune defense than most people appreciate. It produces complement proteins, acute-phase reactants, and other molecules that help the body recognize and fight pathogens. When cirrhosis destroys normal liver tissue and replaces it with scar tissue, these synthetic functions deteriorate. Complement system deficiencies develop, the production of pathogen-recognition receptors drops, and the phagocytic capacity of monocytes and macrophages becomes impaired.⁸

Cirrhosis patients are especially vulnerable to bacterial infections like spontaneous bacterial peritonitis, pneumonia, and urinary tract infections. Infections in this group tend to escalate quickly and carry a high mortality rate, in part because the liver’s impaired synthetic function also hampers the body’s clotting and healing responses. Alcohol-related liver disease is one common pathway to cirrhosis, but hepatitis B, hepatitis C, and nonalcoholic fatty liver disease can all lead to the same immune-compromised endpoint.

Autoimmune Diseases

It may seem contradictory that a disease characterized by an overactive immune system can also cause immunodeficiency, but that is exactly what happens in conditions like systemic lupus erythematosus. Patients with lupus face an inherently elevated risk of infection because the disease itself creates immunological abnormalities that impair the body’s ability to respond normally to pathogens.⁹ The immune system in lupus is dysregulated rather than simply “too active,” with some arms overperforming and others underperforming.

On top of the disease’s own effects, the medications used to control autoimmune flares, corticosteroids, cytotoxic drugs, and newer biologic therapies, each carry their own immunosuppressive burden. The combination of disease-intrinsic immune dysfunction and treatment-induced suppression makes infection one of the leading causes of death in lupus and rheumatoid arthritis. Clinicians managing these patients walk a constant tightrope between controlling the autoimmune process and preserving enough immune function to prevent serious infection.

Severe Burns and Major Trauma

A serious burn or major physical trauma triggers an immune response so intense that it can paradoxically leave the body profoundly immunosuppressed. The initial phase is a massive inflammatory surge, as the body floods the injured area with immune mediators. But this systemic inflammatory response syndrome is followed by a compensatory anti-inflammatory phase in which the immune system essentially overshoots its dampening response and becomes suppressed. In some patients, this sequence progresses into a prolonged state of persistent inflammation, immunosuppression, and catabolism that can last weeks or months.¹⁰

During this immunosuppressed window, burn and trauma patients are extraordinarily vulnerable to hospital-acquired infections, including pneumonia, bloodstream infections, and wound infections. The loss of skin barrier in burn patients adds a direct entry point for bacteria, compounding the immune dysfunction happening internally. Infection remains the leading cause of death in burn patients who survive the initial injury.

Functional or Anatomic Asplenia

The spleen acts as a filter for the bloodstream, trapping bacteria and mounting a rapid antibody response against them. Losing the spleen, whether through surgical removal or through functional destruction from a disease like sickle cell anemia, leaves a specific and dangerous gap in immune defense. Encapsulated bacteria, organisms that coat themselves in a protective shell, are normally the spleen’s specialty. Without it, infections by these organisms can escalate into overwhelming sepsis with alarming speed.

The most dangerous of these bacteria is Streptococcus pneumoniae, which causes the majority of overwhelming post-splenectomy infections. This complication carries a very high mortality rate.¹¹ Vaccination against pneumococcus, meningococcus, and Haemophilus influenzae type b is critical for anyone who has lost splenic function, and many patients also carry standby antibiotics to take at the first sign of fever. People with sickle cell disease often develop functional asplenia in childhood as repeated sickling events damage the organ, which is one reason this group faces lifelong infection risk even without surgery.

Chronic Obstructive Pulmonary Disease

COPD rounds out the list because it illustrates how immune dysfunction can be organ-specific yet still carry serious consequences. In COPD, the alveolar macrophages, immune cells that live in the lung tissue and serve as the first line of defense against inhaled pathogens, become fundamentally impaired. Research has documented that these macrophages lose their ability to effectively engulf common respiratory bacteria like nontypeable Haemophilus influenzae.¹² The macrophages also show dysregulated production of inflammatory mediators and proteases, and impaired ability to clear dead cells.¹³

This localized immune failure is the main reason COPD patients suffer frequent respiratory infections and acute exacerbations. Each infection triggers more inflammation, which damages more lung tissue, which further impairs local immune defense, creating a vicious cycle. Bacterial colonization of the lower airways, something that does not happen in healthy lungs, becomes common in moderate and severe COPD.

Why These Conditions Overlap More Than You Would Expect

In practice, secondary immunodeficiency rarely stems from a single clean cause. An older adult with type 2 diabetes may also have early chronic kidney disease, take corticosteroids for arthritis, eat poorly due to reduced appetite, and have borderline COPD from decades of smoking. Each of those conditions chips away at immune function through different mechanisms, and the cumulative effect is greater than any one factor alone. Aging itself adds another layer: the thymus shrinks with age, naive T-cell production drops, vaccine responses weaken, and a chronic low-grade inflammatory state known as inflammaging settles in.⁶

This stacking of risk factors is a major reason secondary immunodeficiency is underrecognized. No single diagnosis on the problem list may look severe enough to explain why a patient keeps getting infections. But several moderate insults acting in concert can produce profound immune suppression. Clinicians increasingly recognize that evaluating immune function requires looking at the whole picture, not just individual disease labels.

How Secondary Antibody Deficiency Gets Detected

One of the most measurable forms of secondary immunodeficiency is a drop in antibody levels, particularly immunoglobulin G. Blood tests can identify this straightforwardly, yet it is frequently overlooked. Secondary antibody deficiencies are a significant but frequently underrecognized group of acquired immunodeficiencies, arising in settings that include hematologic malignancies, immunosuppressive therapies, and protein-losing conditions.¹⁴

Distinguishing secondary from primary antibody deficiency matters because management can differ. Patients with secondary deficiency tend to retain higher levels of certain antibody subtypes and more functional memory B-cells than those with primary immunodeficiency, though their pre-treatment rates of serious infections requiring hospitalization can actually be higher.¹⁵ In some cases, what appears to be a secondary antibody deficiency turns out to have an underlying inherited component, making the distinction clinically important for long-term management.¹⁶

Treatment Options and What Can Be Reversed

The most important intervention for secondary immunodeficiency is treating or controlling the underlying cause. Bringing blood sugar under control in diabetes, restoring nutrition in malnourished patients, starting antiretroviral therapy in HIV, and achieving remission in blood cancers can each lead to meaningful immune recovery, though the degree varies. As noted with HIV, antiretroviral therapy brings substantial but incomplete restoration of T-cell numbers and function within the first year.

When the underlying cause cannot be fully corrected, or when antibody levels remain dangerously low despite treatment, immunoglobulin replacement therapy becomes an option. This involves regular infusions of pooled antibodies from donated blood. Originally developed for inherited immunodeficiencies, the use of immunoglobulin replacement has expanded significantly over the past two decades to cover secondary deficiencies, particularly those associated with blood cancers and autoimmune disease. It has been shown to reduce the rate of infectious events in these settings, and subcutaneous administration has emerged as a practical, well-tolerated delivery method.¹⁷

Vaccination is another cornerstone, especially for people with conditions like asplenia, chronic kidney disease, or COPD where specific pathogens pose the greatest threat. The challenge is that immunocompromised patients often mount weaker vaccine responses, so timing vaccinations for periods of better immune function, using higher doses, or adding booster schedules can improve protection.

Sleep Deprivation and the Immune System

Beyond the ten diseases discussed above, chronic sleep deprivation has emerged as an underappreciated contributor to immune dysfunction. Sleep supports normal immune function in both the innate and adaptive arms of the system. Chronic sleep loss shifts the body toward a state of low-grade inflammation while simultaneously blunting the immune system’s ability to mount targeted responses against pathogens.¹⁸

The connection appears to run partly through the stress hormone system. Sleep disorders characterized by deprivation, such as insomnia and obstructive sleep apnea, lead to increased activity of the hypothalamic-pituitary-adrenal axis, the same stress-response system that floods the body with cortisol. Since cortisol is a potent immune suppressor, chronic activation of this pathway may explain why poor sleepers show higher rates of infections, weaker vaccine responses, and increased risk for inflammatory diseases.¹⁹ For patients already dealing with one of the diseases on this list, poor sleep quality can compound immune suppression in ways that are easy to overlook and relatively straightforward to address.