Symptoms and How APLAID Affects the Body

Living with APLAID means managing a complex condition where the immune system’s signaling is fundamentally altered. While most people think of the immune system as either working well or being weakened, APLAID causes dysregulation that leads to both inappropriate inflammation and a vulnerability to infection ^[1]. This occurs because of a specific genetic change that disrupts how your body’s defense cells communicate ^[2].

The Genetic Alteration

The root of APLAID is typically a gain-of-function mutation in the PLCG2 gene ^[2]. This gene provides instructions for making a protein called PLCγ2, which acts as a signaling relay within immune cells ^[3].

In APLAID, the mutation alters this signaling pathway, causing it to react abnormally ^[2][4]. This abnormal signaling can trigger the release of inflammatory chemicals even when there is no infection present, leading to systemic inflammation ^[2].

A Two-Front Challenge

Because the PLCγ2 protein is involved in multiple immune pathways, its malfunction creates two different sets of problems:

1. Systemic Autoinflammation: The altered signaling causes the body to trigger inappropriate inflammation, leading to fevers, painful rashes, and organ inflammation ^[1][5].
2. Immune Deficiency: The same abnormal signaling can disrupt the development and function of B cells (the cells that make antibodies) ^[4]. This leads to antibody deficiency, making you more vulnerable to actual bacterial and respiratory infections ^[4][6].

How APLAID Affects the Body

APLAID can cause symptoms in many different organ systems. These symptoms often appear in “flares” that can vary in severity ^[1].

• Skin: This is often an early sign ^[7]. It typically appears as vesiculopustular rashes—small, blistering, or pus-filled bumps—or red, thickened plaques ^[1][7]. While these rashes are primarily driven by internal inflammation, they can still become infected by bacteria or fungi. Any new, changing, draining, or highly painful lesions should be evaluated by a doctor.
• Respiratory System: Due to the antibody deficiency, recurrent infections of the sinuses and chest (like bronchitis) are common ^[1][6]. Over time, repeated inflammation can also lead to structural changes in the lungs, such as interstitial pneumonitis (inflammation of the tissue around the air sacs) ^[1][5].
• Digestive Tract: Some patients develop colitis (inflammation of the colon) or symptoms resembling Inflammatory Bowel Disease (IBD), including chronic diarrhea or abdominal pain ^[8][1].
• Joints and Eyes: Chronic inflammation can lead to arthralgia (joint pain) or severe arthritis ^[9][5]. It can also cause uveitis (serious inflammation inside the eye) or conjunctivitis (inflammation of the surface of the eye) ^[1][10].

APLAID vs. PLAID: Typical Features

You may hear about a related condition called PLAID. While both involve the PLCG2 gene, their clinical patterns typically differ, though some overlap exists:

While the absence of cold-induced hives is a useful clue that points toward APLAID, it is not an absolute rule. Accurate diagnosis requires looking at the specific genetic mutation alongside the clinical symptoms ^[1][10].

Brief Glossary of Terms

• PLCγ2: The protein that relays signals inside immune cells.
• B cells: White blood cells that produce antibodies to fight infections.
• Interstitial pneumonitis: Inflammation of the lung tissue that can affect breathing.
• Uveitis: Serious inflammation deep inside the eye (different from surface redness or ‘pink eye’) that requires prompt medical attention to protect vision.