Differential Diagnosis of Lichen Scrofulosorum

Lichen scrofulosorum is a rare tuberculid that typically presents as a lichenoid eruption in children and adolescents with underlying tuberculosis. The differential diagnosis can be broad, given its varied presentation. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Lichen nitidus: This condition presents with tiny, shiny, flat-topped papules that are often confused with lichen scrofulosorum due to their similar appearance. However, lichen nitidus lacks the characteristic tuberculid features and is not associated with tuberculosis.

• Other Likely Diagnoses

  • Pityriasis lichenoides: This condition can mimic lichen scrofulosorum due to its lichenoid appearance, but it typically lacks a clear association with tuberculosis and has distinct histopathological features.
  • Lichen planus: Although lichen planus can present with lichenoid papules, it usually has a more widespread distribution, mucosal involvement, and characteristic histological features that distinguish it from lichen scrofulosorum.
  • Guttate psoriasis: This form of psoriasis can present with small, lichenoid papules, but it is typically associated with a history of psoriasis, lacks the tuberculid features, and has different histopathological characteristics.

• Do Not Miss Diagnoses

  • Tuberculosis: Given that lichen scrofulosorum is a tuberculid, it is crucial not to miss the diagnosis of underlying tuberculosis. This could be life-threatening if left untreated.
  • Sarcoidosis: Although less common, sarcoidosis can present with skin manifestations that might be confused with lichen scrofulosorum. Missing this diagnosis could lead to significant morbidity due to the systemic nature of sarcoidosis.

• Rare Diagnoses

  • Papulonecrotic tuberculid: This is another form of tuberculid that can present with necrotic papules, which might be confused with lichen scrofulosorum in some cases.
  • Erythema induratum (Bazin disease): A form of tuberculid that primarily affects the calves, presenting with recurrent nodules and ulcers. While distinct, it shares the underlying association with tuberculosis.
  • Lupus miliaris disseminatus faciei (LMDF): A rare condition that presents with small, lichenoid papules on the face, which could be confused with lichen scrofulosorum due to its lichenoid appearance, but it lacks the association with tuberculosis.

Each of these diagnoses requires careful consideration of clinical presentation, histopathological findings, and, when relevant, the patient's tuberculosis status to accurately differentiate lichen scrofulosorum from other conditions.