Differential Diagnosis for Numerous Reticular Modular Lesions on Arms and Legs

Single Most Likely Diagnosis

• Lichen nitidus: A rare skin condition characterized by tiny, shiny, flat-topped bumps that can appear in a reticular or modular pattern, often on the arms and legs. The condition is usually benign and can be diagnosed based on clinical appearance and histopathology.

Other Likely Diagnoses

• Keratosis pilaris: A common skin condition that causes small, rough, sandpaper-like bumps on the skin, often on the arms and legs. While not typically reticular, the modular lesions can sometimes appear in a pattern that might be confused with reticular lesions.
• Lichen planus: An inflammatory condition that affects the skin and mucous membranes, characterized by purplish, itchy, flat bumps. In some cases, lichen planus can present with a reticular pattern, especially on the arms and legs.
• Scleroderma: A group of diseases that result in the hardening and tightening of skin and connective tissue. While scleroderma can cause a variety of skin changes, including modular lesions, it is less likely to present with a purely reticular pattern.

Do Not Miss Diagnoses

• Cutaneous lymphoma: A type of cancer that affects the skin, which can present with a wide range of skin lesions, including reticular or modular patterns. Given the potential severity of this diagnosis, it is crucial not to miss it, even if it is less likely.
• Cutaneous metastases: Spread of cancer from another part of the body to the skin, which can manifest as various types of skin lesions, including those with a reticular or modular appearance. Identifying these lesions as metastatic is critical for the patient's prognosis and treatment.

Rare Diagnoses

• Necrobiotic xanthogranuloma: A rare skin condition characterized by yellowish patches or nodules, which can sometimes appear in a reticular pattern. This condition is often associated with paraproteinemia.
• Reticular erythematous mucinosis: A rare condition that presents with reticular erythema and mucin deposition in the skin, often on the arms and legs. It can be associated with various systemic conditions.
• Sjögren's syndrome: An autoimmune disorder that can cause skin lesions, among other symptoms, including potentially reticular or modular lesions on the arms and legs, though this is less common.