IgG myeloma is the most common subtype of multiple myeloma, a blood cancer that starts in plasma cells, the white blood cells responsible for making antibodies. About 52 to 54% of all multiple myeloma cases are the IgG type, meaning the cancerous plasma cells overproduce a specific antibody called immunoglobulin G. Understanding the subtype matters because it influences how the disease behaves, how it’s monitored, and what complications to watch for.
How IgG Myeloma Develops
Your plasma cells normally produce a mix of different antibodies to fight infections. In IgG myeloma, a single plasma cell becomes malignant and begins cloning itself uncontrollably in the bone marrow. Every one of these identical copies churns out the same IgG antibody, called a monoclonal protein (or M-protein). This flood of one identical antibody crowds out the normal, diverse antibodies your immune system needs. The result is a paradox: your blood is full of antibody protein, yet your actual immune defense is weakened.
This suppression of normal antibody production is called immunoparesis. It’s one reason people with myeloma are significantly more vulnerable to infections, especially bacterial ones like pneumonia. The malignant plasma cells also crowd normal blood-forming cells in the bone marrow and release signals that break down bone tissue, creating a cascade of problems throughout the body.
Common Symptoms
Myeloma symptoms are often summarized by doctors using the acronym CRAB: calcium elevation, renal (kidney) problems, anemia, and bone disease. Not everyone has all four at diagnosis, but these are the hallmarks that signal the disease has moved beyond its earliest, silent stages.
- Bone disease: Over 80 to 90% of myeloma patients develop bone lesions as the cancer progresses. These are holes in the bone where malignant cells have triggered excessive bone breakdown. Nearly 30% of patients experience pathological fractures in the spine or long bones, meaning the bone breaks from normal activity rather than trauma. Persistent back pain is one of the most common first complaints.
- Anemia: As malignant plasma cells fill the bone marrow, there’s less room for red blood cell production. This leads to fatigue, weakness, and shortness of breath.
- Kidney damage: Myeloma cells produce excess light chains (smaller fragments of the antibody) that are filtered through the kidneys. When these fragments overwhelm the kidney’s ability to process them, they form casts that block the tiny tubes inside the kidney, damaging tissue and reducing kidney function. Cast nephropathy accounts for 40 to 63% of kidney problems in myeloma patients.
- High calcium: Bone breakdown releases calcium into the bloodstream. Elevated calcium can cause nausea, confusion, excessive thirst, and constipation.
How IgG Myeloma Is Diagnosed
The cornerstone of diagnosis is a blood test called serum protein electrophoresis (SPEP). This test separates proteins in your blood by electrical charge, and a monoclonal protein shows up as a sharp spike, often called an M-spike. In IgG myeloma patients, the median M-protein level at diagnosis is around 38 grams per liter, though it can range widely. Every patient with IgG myeloma will also show an abnormal ratio between the two types of light chains (kappa and lambda), which helps confirm the diagnosis and track the disease over time.
Beyond blood tests, a bone marrow biopsy confirms the percentage of malignant plasma cells present. Imaging scans, typically CT, PET-CT, or MRI, check for bone lesions. Genetic testing of the myeloma cells is also critical because certain chromosomal abnormalities predict how aggressive the cancer will be.
How It Compares to Other Myeloma Subtypes
Multiple myeloma is classified by which antibody the malignant cells produce. IgG is the most common at roughly 52%, followed by IgA at about 21%, light chain only disease at 16%, and rare subtypes like IgD (2%) and IgM (under 1%). The subtype affects prognosis. IgA myeloma patients tend to have shorter progression-free survival and worse overall survival compared to IgG patients. One study found median survival of 108 months for IgG myeloma versus 80 months for IgA, with the gap becoming more noticeable after the five-year mark.
IgA myeloma also carries a higher rate of certain high-risk genetic changes. About 40% of IgA cases have a specific chromosomal rearrangement called t(4;14), compared to only 13% of IgG cases. These genetic differences help explain why outcomes differ between the subtypes, even when patients receive the same treatments.
Staging and Prognosis
Doctors stage myeloma using the Revised International Staging System (R-ISS), which combines blood markers and genetic findings to sort patients into three risk groups. Stage I carries the best outlook, stage III the worst, and stage II falls in between. In practice, the majority of patients (about 75%) land in stage II at diagnosis, with only around 10% in stage I and 14% in stage III. The system isn’t perfect because stage II is so broad, but it remains the standard tool for estimating prognosis.
For IgG myeloma specifically, the overall outlook is somewhat more favorable than for some other subtypes. Median survival for IgG patients has reached about 108 months (nine years) in modern studies, though individual outcomes vary enormously depending on staging, genetics, age, kidney function, and response to treatment.
Treatment Approach
Treatment for IgG myeloma follows the same general framework as other myeloma subtypes, with the subtype influencing monitoring more than the choice of therapy. The standard approach uses combinations of three or four drugs.
For patients healthy enough for a stem cell transplant (generally younger or fitter individuals), treatment typically starts with an induction phase using a three-drug combination. The most widely accepted regimen pairs a proteasome inhibitor with an immunomodulatory drug and a steroid. In some cases, a fourth drug, a targeted antibody, is added upfront for patients expected to need a stronger initial response. After several cycles of induction, patients undergo an autologous stem cell transplant using their own previously collected stem cells, followed by maintenance therapy that can continue for years.
For patients who aren’t candidates for transplant, often due to age or other health conditions, similar drug combinations are used at adjusted doses. Two-drug or three-drug regimens with a targeted antibody have shown strong results in this group and are increasingly considered standard.
Myeloma is not currently considered curable in most cases, but many patients achieve deep remissions that last years. The goal of treatment is to reduce the M-protein to undetectable levels and keep it suppressed for as long as possible.
Kidney and Bone Complications
Kidney damage deserves special attention in IgG myeloma. While light chain myeloma is most strongly associated with kidney problems, any myeloma subtype can cause renal injury through excess light chains. The mechanism is straightforward: light chains flood the kidney’s filtering system, overwhelm the cells lining the kidney tubules, and trigger inflammation and obstruction. Starting myeloma treatment quickly is the most effective way to protect kidney function, because reducing the tumor burden lowers light chain production.
Bone disease in myeloma is unique among cancers. Unlike most cancers that spread to bone, myeloma creates purely destructive lesions without the new bone formation that other cancers sometimes trigger. This means bone lesions in myeloma rarely heal on their own, even after successful treatment. Supportive care with bone-strengthening medications is standard, and radiation therapy or surgical stabilization may be needed for painful or structurally dangerous lesions.
Monitoring After Diagnosis
One practical advantage of IgG myeloma compared to some subtypes is that the M-protein is reliably measurable on standard blood tests. This makes tracking treatment response relatively straightforward. Your medical team will repeat SPEP and light chain tests at regular intervals to see whether the M-protein is falling, stable, or rising. A rising M-protein after treatment is one of the earliest signs of relapse, often appearing before any symptoms return. This gives doctors a window to adjust therapy before complications develop.