Differential Diagnosis for Bilateral Axillae Rash

• Single most likely diagnosis
  • Contact dermatitis: This is a common condition that can occur due to irritation from deodorants, soaps, or other substances that come into contact with the skin in the axillary region. The bilateral presentation suggests an external cause rather than a systemic one.
• Other Likely diagnoses
  • Intertrigo: A type of skin inflammation caused by skin-on-skin friction, often in warm, moist areas like the axillae. It can be exacerbated by sweating and poor hygiene.
  • Eczema (atopic dermatitis): Although more commonly associated with flexural areas, eczema can occur in the axillae, especially in individuals with a history of atopic diseases.
  • Seborrheic dermatitis: This condition can cause a rash in areas rich with sebaceous glands, including the axillae, though it's more commonly associated with the scalp, face, and torso.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Lymphoma: Certain types of lymphoma, like cutaneous T-cell lymphoma, can present with skin lesions or rashes in unusual locations, including the axillae. Although rare, missing this diagnosis could have severe consequences.
  • Invasive breast cancer: In rare cases, axillary skin changes can be a sign of underlying breast cancer, particularly if there's associated lymphedema or peau d'orange.
• Rare diagnoses
  • Hailey-Hailey disease (familial benign pemphigus): A rare genetic disorder that causes blistering skin lesions, often in the axillae and groin, due to a defect in the ATP2C1 gene.
  • Darier disease: A rare genetic disorder that affects the skin and sometimes the nails and mucous membranes, causing a rash that can appear in the axillae among other areas.