What sex and gender differences exist in the prevalence, clinical presentation, and treatment response of autoimmune diseases between men and women?

Sex and Gender Differences in Autoimmune Disorders

Women are disproportionately affected by autoimmune diseases with a 3-4:1 female-to-male ratio, but men experience more severe disease courses, higher mortality rates, and worse treatment outcomes across multiple autoimmune conditions.

Prevalence Disparities

The female predominance in autoimmune diseases is striking and consistent across conditions:

• Autoimmune hepatitis shows a 3-4:1 female-to-male ratio, though this gap has narrowed over time with relative increases in male patients 1
• Systemic lupus erythematosus (SLE) affects women three times more frequently than men 2
• Multiple sclerosis demonstrates women are three times more likely to develop the disease and tend to present symptoms earlier 3
• Systemic sclerosis shows higher female prevalence, though men experience more severe manifestations 4

Women also demonstrate higher rates of autoimmune multimorbidity—the co-occurrence of multiple autoimmune conditions. For example, 30.2% of women with SLE have at least one additional autoimmune disease compared to 25.4% of men, and 31.6% of women with Sjögren's syndrome versus 20.7% of men 5.

Clinical Presentation and Disease Severity

Despite lower prevalence, men consistently experience worse clinical outcomes:

• Male patients with autoimmune hepatitis have worse hospital outcomes, higher rates of disease complications, higher hospital costs, and increased AIH-related mortality compared to females 1
• Men with systemic sclerosis more frequently develop diffuse cutaneous involvement, interstitial lung disease, and have reduced survival 4
• Males with multiple sclerosis experience more aggressive disease forms 3

These differences likely stem from gender-related comorbidities, sex-related immunogenetic differences, variations in the hypothalamic-pituitary-gonadal system, sex hormone influences on disease activity, and differences in medical adherence 1.

Biological Mechanisms Underlying Sex Differences

Hormonal Influences

Estrogens act as potent stimulators of autoimmunity while androgens play protective roles 6. Sex hormones affect immune cells and responses directly and may induce epigenetic DNA changes 2. The immunomodulatory effects of sex hormones explain why:

• Females mount stronger immune responses than males 2
• Reproductive stage is a key variable in disease expression and drug response 3
• Disease activity may fluctuate with hormonal changes including menopause 4

X-Chromosome Genetics

The X-chromosome contains critical immune-related genes including FOXP3, TLR7, TLR8, CD40 Ligand, IL2RG, IL9R, and BTK 2. Key mechanisms include:

• X-chromosome gene dosage: Approximately 25% of X-linked genes escape inactivation, resulting in higher gene dosage in females 2
• Klinefelter syndrome evidence: Men with 47,XXY (extra X-chromosome) develop SLE as frequently as women, demonstrating the direct impact of X-chromosome dosage 2
• Random X-inactivation patterns and regulation of immune-related genes vary between sexes 4

Immune Response Differences

Females and males differ fundamentally in immune cell composition and function 2:

• Females generally mount stronger innate and adaptive immune responses 7
• Sex-specific differences exist in metabolic regulation of immune cells 8
• Estrous cycles in females induce variability in immune traits 8

Treatment Response Variations

Treatment efficacy demonstrates clear sex-based patterns:

Immunostimulatory Therapies

Females develop greater responses to immunotherapies aimed at stimulating immune responses (e.g., influenza vaccines) and may experience greater efficacy 9.

Immunosuppressive Therapies

Males reportedly experience greater efficacy with immunotherapies that repress immune responses, including:

• TNF inhibitors for rheumatoid arthritis 9
• Checkpoint inhibitors for melanoma 9

Adverse Events

Females experience more adverse reactions than males following biologic immunotherapies 9. Women with multiple sclerosis respond better to certain disease-modifying drugs 3, though treatment responses may vary by sex across conditions 4.

Environmental and Lifestyle Interactions

Environmental factors interact with sex-specific biology to shape autoimmune risk, including smoking, infections, and gut microbiome composition 7. Gender as a sociocultural factor—involving roles, behaviors, and healthcare access—may further modify disease perception, healthcare engagement, and outcomes, though this remains underexplored 4.

Clinical Implications and Pitfalls

Common pitfalls to avoid:

• Assuming female predominance means worse outcomes: Men consistently have higher mortality and more severe disease despite lower prevalence
• One-size-fits-all treatment approaches: Sex and gender contribute to variable treatment success, adherence, and toxicity profiles 9
• Ignoring autoimmune multimorbidity screening: Approximately 20% of patients have extrahepatic autoimmune diseases at diagnosis, with an additional 13% developing new autoimmunity within 5 years; presence of multiple autoimmune diseases increases all-cause mortality 1

Key screening considerations:

• Screen for thyroid disorders (8-18%), skin conditions (8%), inflammatory bowel disease (4-22%), and celiac disease (4% in adults, 11-46% in children) in patients with autoimmune hepatitis 1
• First-degree relatives are at increased risk and warrant surveillance 1

The current gap in sex-stratified clinical research limits precision medicine approaches 7. Recognizing sex as a fundamental biological variable is essential for developing more effective, tailored therapeutic strategies 7.