Differential Diagnosis for Small Circular "Bumps" Filled with Fluid

The patient's symptoms of small circular "bumps" that are mostly flat but appear filled with fluid across the entire body can be approached by considering various dermatological and systemic conditions. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Urticaria: This condition is characterized by itchy, raised hives that can appear anywhere on the body. The hives are often circular and can be filled with fluid, making them a strong candidate for the described symptoms. Urticaria can be acute or chronic and has various triggers, including allergic reactions, infections, and autoimmune disorders.

• Other Likely Diagnoses

  • Papular Urticaria: A type of skin reaction often caused by insect bites, leading to small, itchy bumps.
  • Dyshidrotic Eczema: A condition that causes small, fluid-filled blisters on the hands and feet, but can sometimes appear on other parts of the body.
  • Keratosis Pilaris: Although not typically fluid-filled, this condition causes small, rough bumps on the skin, often on the arms, legs, and buttocks, and could be considered if the fluid aspect is less prominent.

• Do Not Miss Diagnoses

  • Bullous Pemphigoid: An autoimmune disease that causes large, fluid-filled blisters. While the blisters are typically larger than those described, it's crucial not to miss this diagnosis due to its potential severity and the need for specific treatment.
  • Pemphigus Vulgaris: Another autoimmune disease that leads to blistering of the skin and mucous membranes. The blisters can be filled with fluid and may initially appear as small, circular bumps.
  • Staphylococcal Scalded Skin Syndrome (SSSS): A condition caused by staphylococcal toxins that can lead to widespread blistering of the skin. It's more common in children but can occur in adults, especially those with compromised immune systems.

• Rare Diagnoses

  • Epidermolysis Bullosa: A group of genetic conditions that result in fragile skin and blisters. While rare, it's an important consideration, especially if the condition is congenital or appears in early childhood.
  • Darier Disease: A rare genetic disorder that affects the skin, leading to abnormal keratinization and resulting in greasy, crusted bumps or blisters, particularly on the torso.

Each of these conditions has distinct features, and a thorough clinical evaluation, including history, physical examination, and potentially diagnostic tests (like skin biopsies or blood tests), is necessary to determine the correct diagnosis.