Armpit Rash Differential Diagnosis

The differential diagnosis for an armpit rash can be extensive, given the variety of potential causes. Here's a categorized approach to consider the possible diagnoses:

• Single Most Likely Diagnosis

  • Contact dermatitis: This is often the most common cause of an armpit rash, resulting from irritation or allergic reactions to antiperspirants, deodorants, or other substances that come into contact with the skin in this area.

• Other Likely Diagnoses

  • Intertrigo: A type of skin inflammation caused by skin friction and moisture, common in warm, humid environments or in individuals with obesity.
  • Eczema (atopic dermatitis): Can manifest in the armpits, especially in individuals with a history of atopic diseases.
  • Fungal infections (e.g., candidiasis): Warm, moist areas like the armpits are prone to fungal growth.
  • Bacterial infections: Such as folliculitis or impetigo, which can cause rashes and other skin symptoms in the armpit area.

• Do Not Miss Diagnoses

  • Lymphoma: Although rare, cutaneous T-cell lymphoma (e.g., mycosis fungoides) can initially present with skin lesions in unusual areas, including the armpits.
  • Invasive breast cancer: In rare cases, an armpit rash could be a sign of Paget's disease of the breast or another form of breast cancer that has spread to the skin.
  • Tuberculosis: Cutaneous tuberculosis is rare but can present with skin lesions in various parts of the body, including the armpits.

• Rare Diagnoses

  • Granuloma glutiale infantum: A rare condition causing skin lesions in the diaper area of infants but can occasionally be seen in adults in areas like the armpits.
  • Hailey-Hailey disease (familial benign pemphigus): A rare genetic disorder that affects the skin, causing blisters and erosions, often in intertriginous areas like the armpits.
  • Fox-Fordyce disease: A rare skin condition characterized by the blockage of apocrine sweat glands, leading to itchy, dome-shaped bumps or papules in areas like the armpits.

Each of these diagnoses has distinct characteristics and risk factors, and a thorough medical history, physical examination, and sometimes diagnostic tests are necessary to determine the underlying cause of an armpit rash.