Differential Diagnosis

• Single most likely diagnosis
  • Cervical Lymphadenitis or Cellulitis: The patient presents with stiffness and pain in the neck, a new rash on the left side of the neck that does not completely blanch, and swelling in the right orbital region. These symptoms, combined with the absence of systemic symptoms like fever, photophobia, or vomiting, suggest a localized infection. The rash and swelling could be indicative of a bacterial or viral infection causing lymphadenitis or cellulitis.
• Other Likely diagnoses
  • Dermatological conditions (e.g., Contact Dermatitis, Eczema): The rash on the left side of the neck could be due to a dermatological condition, especially if it's not completely blanching, suggesting possible inflammation or infection of the skin.
  • Allergic Reaction: An allergic reaction could explain the rash and swelling, especially if the patient has been exposed to new substances or has a history of allergies.
  • Insect Bite or Sting: Given the localized nature of the symptoms, an insect bite or sting could be a possible cause, especially if the rash is itchy or has a central punctum.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Meningitis: Although the patient does not have classic symptoms like fever, photophobia, or headache, meningitis can present atypically, especially in the early stages or in certain populations. The neck stiffness is a red flag that necessitates consideration of this diagnosis.
  • Lymphoma or Leukemia: Unexplained lymphadenopathy (swelling of the lymph nodes) could be a sign of a hematological malignancy. Although less likely given the acute presentation, it's a diagnosis that could have significant implications if missed.
  • Orbital Cellulitis: The swelling and tenderness in the right orbital region could indicate orbital cellulitis, a serious infection that requires prompt treatment to prevent complications like vision loss.
• Rare diagnoses
  • Kawasaki Disease: This condition, which mainly affects children, can cause rash, fever (though the patient is afebrile), and lymphadenopathy. It's a rare cause of these symptoms but is important to consider due to its potential for cardiac complications.
  • Relapsing Polychondritis: This rare autoimmune disorder can cause inflammation of cartilaginous structures, including those in the ears, nose, and eyes, and can also present with skin lesions and lymphadenopathy.
  • Sarcoidosis: A systemic granulomatous disease that can affect multiple organs, including the skin, eyes, and lymph nodes, though it would be unusual for it to present so acutely.