Wednesday, December 9, 2009

Back to the Z - the Zebras: Macrophage Activation Syndrome and Hemophagocytic Syndrome

I'm finishing another week in the Pediatrics wards. It has been a truly exciting journey, and we are finishing it with cases seen more commonly in the subspecialty grounds and that my training as an internist helps me to approach it from several perspectives before having the subspecialists involved.

A fascinating case of a child admitted with intermittent fever, mild anemia and lymphopenia and generalized lymphadenopathy and hepatosplenomegaly. The most common cause of a mononucleosis like picture will be a viral disease; but this child had negative Epstein Barr, Citomegalovirus, Herpes simplex and Hepatitis serologies; his PPD is pending and has no exposure to cats suggesting an infection with Bartonella henselae which can cause bacillary angiomatosis, or an infection with Toxoplasma sp. Most likely he will benefit from an histopathologic diagnosis. However, the fascinating issue is the differential that can outsource from a patient with hepatosplenomegaly, fever, cytopenias, which includes infectious causes as above, malignancy such as lymphomas and as well systemic inflammatory diseases like Hemophagocytic lymphohistiocytosis also known as hemophagocytic syndrome as well as a subset of this disease known as Macrophage Activation Syndrome.

I brought to my resident's attention my interest in ruling out this as part of the work-up prior to obtaining a lymph node biopsy. It was interesting to find out their surprise with the unknown names and their immediate curiosity about its place in the diagnostic puzzle. I told them..."your eyes can see what your brain knows". It is my responsibility to expand my own knowledge, but to make sure I share this knowledge with other colleagues and especially the residents and medical students.

So, what are macrophage activation syndrome and hemophagocytic syndrome? these are significant inflammatory conditions, usually occurring in patients with Juvenile Rheumatoid Arthritis or Juvenile Systemic Lupus Erythematosus. Its etiology is unknown, but it has been proposed that it is due to an abnormal regulation of the macrophage-lymphocyte interaction with secondary increase of cytokines (TNF-alpha, IL-1, IL-6, IFN-gamma, soluble IL-2 receptors and soluble TNF receptor; all of these cytokines are derived from T-cells and macrophages. Both can be life threatening if unrecognized. Usually, it is clinically characterized by persistent fever, generalized lymphadenopathy, hepatosplenomegaly, a Disseminated intravascular coagulation profile with thrombocytopenia, low fibrinogen levels, and prolongation of coagulation times; secondary to coagulopathy, can manifest with hemorrhages in any part of the body. It can be associated with pancytopenia (usually bicitopenia), elevated ferritin, transaminitis, and hematophagocytic histiocytes in the bone marrow. Its mortality can reach almost 50% of the cases. An interesting confusing picture is the elevated ferritin, which can by itself be a manifestation of Still's disease and as an acute phase reactant. The treatment is aimed to control the intense inflammatory response, using systemic immunosupressants such as steroids in elevated doses, cyclosporine A, IVIG, TNF-alpha inhibitors, anakinra, etc. However, this is a competence of the Hematologist and the Rheumatologist not of the hospitalist.

In addition to the excellent reference that is UpToDate, I always aim to look into PubMed for newer and updated references (such as the ones I post almost on a daily basis in my Twitter account "medpedshosp"). This time I was lucky enough in finding a very good reference from Dr. Tristano at Med Sci Monit, 2008; 14(3): 27-36. As well a very updated reference from Dr. Karras in Nature Reviews Nephrology. Jun 2009; 5: 329-36.

My residents received today an email including these references, as well as other based on our morning discussion (utility of anti-cyclic citrullinated peptide antibodies in the diagnosis of Rheumatoid arthritis - I emailed them 3 articles - a review from the Ann NY Acad Sci, and another from The Journal of Rheumatology.).

Tomorrow will be an interesting academic round after they have reviewed this articles.

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