Neutropenia and neutrophil disorders: Viva

Branching clinical structured oral on neutropenia and the neutrophil disorders in children. Covers the recognition and first-hour management of febrile severe neutropenia, the absolute-neutrophil-count thresholds and the severity grading, the neutrophil kinetic model that localises the mechanism, the workup of the incidental chronic isolated neutropenia including anti-neutrophil antibodies and a gene panel, the congenital syndromes (severe congenital neutropenia, cyclic neutropenia, Shwachman-Diamond, GATA2 deficiency, WHIM, Chediak-Higashi), the role of granulocyte colony-stimulating factor and haematopoietic stem cell transplant, and the counselling for autoimmune neutropenia of infancy and benign ethnic neutropenia.

branching clinical structured oral4 min readVerification in progress

Prompt

A nine-month-old boy of West African ancestry is brought to the general paediatric clinic. He had a viral upper respiratory illness two weeks ago. A full blood count taken for a febrile episode three days ago showed an absolute neutrophil count of 0.6 times ten to the ninth per litre with a normal haemoglobin and platelet count. He is now afebrile and well. The examiner asks for your structured approach.

Branch 1: The first move and the definition

The candidate should immediately reframe the picture: an incidental isolated neutropenia in a well infant two weeks after a viral illness, most likely a benign transient post-viral dip, but to be confirmed. The first move is to repeat the full blood count on a fresh sample and to examine the peripheral film, because ethylenediaminetetraacetic-acid clumping and transient post-viral dips are common, and a single low count is never a diagnosis. The candidate should state the thresholds aloud: neutropenia is an absolute neutrophil count under 1.5 times ten to the ninth per litre, graded as mild 1.0 to 1.5, moderate 0.5 to 1.0, and severe under 0.5, with the absolute neutrophil count calculated as the white cell count times the percentage of segmented neutrophils plus bands divided by one hundred. [1]

The examiner will probe why the count is calculated and why the bands matter. The candidate should explain that the circulating pool is the fraction sampled by a full blood count, that the marginated pool is roughly equal in size, and that including the band cells in the absolute neutrophil count matters because they are the immediate neutrophil reserve. The examiner may ask what a low count in a child of African ancestry means. The candidate should name benign ethnic neutropenia, caused by the Duffy-null regulatory variant in the ACKR1 gene, with a normal marginated pool and normal function and no infection excess, and stress that recognising it prevents over-investigation. [11]

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References5Show ledger

[1]Newburger PE, Dale DC Evaluation and management of patients with isolated neutropenia. Semin Hematol, 2013.PMID 23953336
[2]Welte K, Zeidler C, Dale DC Severe congenital neutropenia. Semin Hematol, 2006.PMID 16822461
[3]Dale DC, Cottle TE, Fier CJ, et al Severe chronic neutropenia: treatment and follow-up of patients in the Severe Chronic Neutropenia International Registry. Am J Hematol, 2003.PMID 12555210
[5]Makaryan V, Zeidler C, Bolyard AA, et al The diversity of mutations and clinical outcomes for ELANE-associated neutropenia. Curr Opin Hematol, 2015.PMID 25427142
[11]Reich D, Nalls MA, Kao WH, et al Reduced neutrophil count in people of African descent is due to a regulatory variant in the Duffy antigen receptor for chemokines gene. PLoS Genet, 2009.PMID 19180233