A 13 year old girl with history of lethargy, joint pain and cough....

A 13 years old girl presented to accident and emergency department with a history of lethargy, joint pain and cough. Both of her parents are from Jamaica. Her problem started one month ago with an upper respiratory infection. She was seen by her family doctor and diagnosed to have a viral infection. She has a past history of skin rashes that was never seen by her family doctor.
On examination she has a palpable cervical lymph nodes of various sizes, a congested throat, generalized myalgia and a swollen ankle joint on the left side.
Her BP is 120/75 mmHg, HR 90 bmp, RR 22/min.
A urine test shows protein+ve with red cells.
other tests are as follows:
Hb = 9.7 g/dl
TLC = 4x10-9/l with neutrophils and lymphopenia.
Platelets =100x10-9/l
Retic count = 2.6%
CRP = 20

Questions:
1. Which three other investigations should be carried out?
2. What treatments should you prescribe?
3. What are three possible differential diagnosis?

Answers: