Differential Diagnosis for a 16-year-old Girl with Rash and Joint Pain
- Single most likely diagnosis
- Infectious Mononucleosis (Mono): The patient's symptoms, including a maculopapular rash, fever, fatigue, lymphadenopathy, and joint pain, are consistent with infectious mononucleosis, particularly given her age and sexual activity. The rash and lymphadenopathy are common presentations of this illness.
- Other Likely diagnoses
- Lyme Disease: Although less common, Lyme disease can present with a rash (erythema migrans) and joint pain, especially if the patient has been exposed to ticks. However, the rash in Lyme disease typically starts as a single lesion and expands, which is different from the patient's presentation.
- Streptococcal Infection: A streptococcal infection, such as scarlet fever, could explain the rash and fever. However, the absence of a sore throat and the specific characteristics of the rash make this less likely.
- Viral Exanthem: Various viral infections can cause rashes and systemic symptoms. The patient's presentation could fit a viral exanthem, but the specific pattern and accompanying lymphadenopathy and joint pain suggest other diagnoses might be more likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Meningococcemia: Although the patient does not have neck stiffness, nausea, or vomiting, meningococcemia can present with a rash and fever. It is crucial to consider this diagnosis due to its high mortality rate if not promptly treated.
- Disseminated Gonococcal Infection (DGI): Given the patient's sexual activity, DGI is a critical diagnosis not to miss. It can present with a rash, joint pain, and fever, although the rash in DGI is typically more localized and the patient often has symptoms of a sexually transmitted infection.
- Rheumatic Fever: This condition, following a streptococcal infection, can cause joint pain and fever but typically includes other major criteria like carditis or chorea. The rash is not a primary feature, but it's essential to consider due to the potential for serious cardiac complications.
- Rare diagnoses
- Kawasaki Disease: Although more common in younger children, Kawasaki disease can occur in adolescents and presents with fever, rash, lymphadenopathy, and desquamation of the hands and feet. The patient's age and the specific pattern of the rash make this less likely.
- Systemic Lupus Erythematosus (SLE): SLE can cause a malar rash, joint pain, and fever, among other symptoms. However, the diagnosis of SLE typically requires a combination of clinical and immunological criteria, making it a less likely initial diagnosis without further testing.
- Juvenile Idiopathic Arthritis (JIA): JIA can present with joint pain and fever, and some subtypes include a rash. However, the systemic features and the specific rash described would be unusual for JIA without other characteristic findings.