Differential Diagnosis for Diffuse Petechie Rash that Itches
- Single most likely diagnosis
- Urticaria: This is the most likely diagnosis due to the presence of a diffuse petechie rash that itches. Urticaria, also known as hives, is a common condition characterized by itchy, raised welts on the skin. The petechie rash can be a variant of urticaria, especially if it's caused by an allergic reaction or autoimmune disorder.
- Other Likely diagnoses
- Atopic dermatitis (eczema): This condition is characterized by itchy, inflamed skin, and can sometimes present with a petechie rash. Atopic dermatitis is a common condition, especially in children, and can be triggered by allergies, irritants, or environmental factors.
- Insect bite reactions: Insect bites can cause a diffuse petechie rash that itches, especially if the individual has an allergic reaction to the bite. This is a common and likely diagnosis, especially during peak insect seasons.
- Contact dermatitis: This condition occurs when the skin comes into contact with an irritant or allergen, causing an itchy, inflamed rash. Contact dermatitis can present with a petechie rash, especially if the individual has a severe reaction.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Thrombocytopenia: This is a condition characterized by low platelet count, which can cause a petechie rash due to bleeding under the skin. Thrombocytopenia can be life-threatening if left untreated, making it a crucial diagnosis to consider.
- Leukemia: Certain types of leukemia, such as acute lymphoblastic leukemia (ALL), can cause a petechie rash due to bone marrow failure. Leukemia is a life-threatening condition that requires prompt diagnosis and treatment.
- Vasculitis: This is a condition characterized by inflammation of the blood vessels, which can cause a petechie rash. Vasculitis can be life-threatening if left untreated, especially if it affects vital organs.
- Rare diagnoses
- Mastocytosis: This is a rare condition characterized by an accumulation of mast cells in the skin, which can cause a petechie rash. Mastocytosis is often associated with other symptoms, such as flushing and gastrointestinal issues.
- Ehlers-Danlos syndrome: This is a rare genetic disorder that affects the skin, joints, and blood vessels. Ehlers-Danlos syndrome can cause a petechie rash due to fragile blood vessels and skin.
- Scurvy: This is a rare condition caused by vitamin C deficiency, which can cause a petechie rash due to blood vessel fragility. Scurvy is often associated with other symptoms, such as fatigue and joint pain.