n WHICH TESTS AND PROCEDURES WILL MY CHILD NEED? To make the diagnosis of HLH, the following tests will need to be done: • physical exam to check for fever and a big spleen or liver • bloodwork – complete blood count – ferritin – triglycerides – fibrinogen – liver enzymes
– clotting studies – NK cell function – other special tests to evaluate immune system function • biopsy, usually of bone marrow, but can also biopsy other tissue.
n HOW ARE PATIENTS WITH HLH CLASSIFIED OR STAGED? There are two forms of the disease: • inherited form (called familial HLH [FHLH] or primary HLH)—usually diagnosed in children youn- ger than 2 years of age, and there is often a family history of unexplained deaths • acquired form —usually associated with infection, malignancy, or preexisting autoimmune disease (such as juvenile rheumatoid arthritis). It is not possible to tell the difference between the two forms of the disease at the time of diagnosis. The initial treatment is the same for either form of the disease. The only way to be sure that a child has the inherited form of HLH is to do blood tests that look for one of the five known genetic defects that have been linked to HLH: PRF-1, Munc 13-4, STX-11, RAB27A, and STXBP2. There also may be other gene defects associated with HLH that have not been identified yet. Certain rare syndromes have also been linked to HLH, such as Chediak-Higashi syndrome, Griscelli syn- drome, and X-linked lymphoproliferative syndrome.
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