Symptoms, Infections, and Warning Signs

Monitoring your child’s health with IL21R deficiency requires a shift in perspective. Because their immune system cannot “hear” the signals it needs to fight off germs, infections that might be minor in other children can become serious very quickly.

Common Types of Infection

Children with this condition often face a wide variety of infections. The numbers below come from a 2021 study of a very small group (13 children) with this condition ^[1]. These percentages are observations from that specific cohort, not a prediction of exactly what will happen to your child.

• Bacterial Infections (observed in 84.6% of the cohort): These are the most frequent challenge, often affecting the ears, sinuses, and lungs, frequently returning even after treatment ^[1].
• Fungal Infections (observed in 46.2% of the cohort): Your child may be more prone to unusual fungal infections that require specialized antifungal medications ^[1].
• Viral Infections (observed in 38.5% of the cohort): Common viruses can be more severe, and some, like Cytomegalovirus (CMV), have the potential to cause life-threatening pneumonia in susceptible children ^[2][3].

The Threat of Cryptosporidiosis-Associated Cholangitis

One of the most specific risks for a child with IL21R deficiency is a parasite called Cryptosporidium. While this parasite usually causes temporary diarrhea in most people, it can become a chronic, dangerous infection in a child with this condition ^[1][4].

In the 13-patient study cohort, nearly half (46.2%) developed cholangitis, a severe inflammation of the bile ducts in the liver caused by this parasite ^[1]. If the parasite moves from the intestines into the liver and bile ducts, it can cause lasting damage ^[4][5].

Symptoms that the infection may be affecting the liver include:

• Jaundice: A yellowing of the skin or the whites of the eyes ^[1].
• Pain: Persistent pain in the upper right side of the abdomen.
• Stool and Urine Changes: Very pale (clay-colored) stools or very dark (tea-colored) urine ^[1].
• Chronic Diarrhea: Watery diarrhea that does not go away ^[6][2].

Non-Infectious Symptoms

The immune system’s communication breakdown can also lead to issues that aren’t caused by germs. In the 2021 study cohort, these non-infectious manifestations included ^[1]:

• Asthma: Observed in about 23% of the children ^[1].
• Inflammatory Skin Disease: Observed in roughly 15%, looking like severe eczema or a persistent red rash ^[1][2].
• Recurrent Anaphylaxis: A small number (about 8% in the cohort) experienced severe allergic reactions called anaphylaxis ^[1]. Ask your doctor for a personalized allergy action plan and whether your child needs an epinephrine autoinjector.

Emergency Red Flags: When to Seek Immediate Care

Ask your immunology team for a printable emergency action plan that lists your child’s diagnosis, baseline, medications, and the nearest appropriate hospital. If you notice any of the following “Red Flag” symptoms, seek emergency medical attention immediately.

Fever and Sepsis (System-Wide Infection)

• A fever that reaches your child’s specific threshold. Ask your immunologist for a written temperature threshold (often around 38.0°C/100.4°F). Do NOT wait to see if fever-reducing medicine lowers the temperature. Response to an antipyretic does not mean the child is safe ^[7].
• Remember: Serious infections can sometimes happen with a low temperature, or no fever at all.
• Your child is unusually sleepy, difficult to wake up, lethargic, or seems confused ^[8].
• The heart is beating much faster than normal while the child is resting ^[9].

Respiratory Distress (Breathing Emergencies)

• Your child is working hard to breathe (you see the skin pulling in around the ribs or neck).
• Grunting sounds while breathing or a blue/gray tint to the lips or fingernails ^[10][11].
• Your child is too breathless to talk, eat, or drink.

Liver and Bile Duct Emergencies

• Sudden onset of yellowing of the eyes or skin (jaundice) ^[1].
• Severe, worsening abdominal pain, especially if accompanied by vomiting or fever.

Anaphylaxis (Severe Allergic Reaction)

• Difficulty breathing, swelling of the face/throat, sudden hives, or vomiting. Administer an epinephrine autoinjector immediately if prescribed, and call emergency services.

When you arrive at the emergency room, tell the staff immediately that your child has a combined immunodeficiency and is at high risk for sepsis (a life-threatening response to infection) and opportunistic infections (infections that occur more frequently and are more severe in individuals with weakened immune systems).