Differential Diagnosis for Scattered Macules with Intense Diffuse Skin Burning

Single Most Likely Diagnosis

• Polymorphic Light Eruption (PMLE): This condition is characterized by an itchy, burning rash that appears after sun exposure, which could be exacerbated by hot showers and air conditioning (AC) due to the sudden change in temperature and humidity. The scattered macules and the worsening of symptoms with hot showers and AC align with the typical presentation of PMLE.

Other Likely Diagnoses

• Phototoxicity: Certain medications or substances can cause phototoxic reactions, leading to skin burning and macules upon exposure to sunlight. The symptoms worsening with hot showers and AC could be due to increased blood flow and sensitivity.
• Contact Dermatitis: Allergic or irritant contact dermatitis could present with scattered macules and intense burning, especially if the causative agent is something the patient comes into contact with frequently, such as soaps or detergents used in showers.
• Erythema Multiforme: A skin condition characterized by target lesions and can be triggered by infections or medications. While it typically presents with more distinct target lesions, some forms can appear as scattered macules with burning sensations.

Do Not Miss Diagnoses

• Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN): Although rare, these conditions are life-threatening and can start with nonspecific symptoms such as skin burning and macules before progressing to widespread skin detachment. Medications are a common trigger, and the condition can be exacerbated by factors that increase skin sensitivity.
• Cutaneous T-Cell Lymphoma (CTCL): Certain types of CTCL, like mycosis fungoides, can present with skin burning and macules. While less common, missing this diagnosis could lead to significant morbidity.

Rare Diagnoses

• Erythropoietic Protoporphyria (EPP): A rare genetic disorder that leads to sensitivity to sunlight, causing burning pain, and sometimes blistering. The symptoms can be exacerbated by heat and could potentially worsen with hot showers.
• Solar Urticaria: A rare condition where exposure to sunlight leads to the development of wheals (hives) and can be accompanied by burning sensations. The reaction typically occurs within minutes of sun exposure and resolves once the individual is no longer exposed to sunlight.