Screening Study for KIT D816V Mutated Mast Cell Disease in Select Populations

This study is screening people with certain conditions to find out if they have a specific genetic mutation (KIT D816V) linked to a disease called mast cell disease. Mast cells are immune cells that, when overactive or abnormal, can cause a range of symptoms. This study aims to identify undiagnosed mast cell disease in people with related conditions. **You may be eligible if...** - You have a history of severe allergic reactions (anaphylaxis), especially to bee/wasp stings or without a clear trigger, OR - You have episodes of unexplained symptoms affecting your skin, breathing, gut, or heart that respond to antihistamines or mast cell mediator treatments, OR - You have hypermobile Ehlers-Danlos syndrome, postural tachycardia syndrome (POTS), or early-onset bone loss (osteoporosis/osteopenia), OR - You have a bone marrow condition called chronic myelomonocytic leukemia or myelodysplastic syndrome **You may NOT be eligible if...** - You have already been diagnosed with systemic mastocytosis, mast cell sarcoma, or a known KIT mutation in mast cells - Your bone loss is explained by another known cause (hormonal, nutritional, or genetic) Talk to your doctor to see if this trial is right for you.