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Platelet Esoteric Testing

A Case Study



Laboratory Systemic Approach

Slide 13

June 2010

Laboratory diagnosis of a hereditary platelet disorder requires a systemic approach. It starts with a clinical finding including patient’s personal and family bleeding history and bleeding pattern. Patients with hereditary platelet disorder commonly present with mild to moderate thrombocytopenia and mucocutaneous bleeding.

Next, the possibility of a plasmatic hemostatic deficiency such as von Willebrand disease (VWD) and acquired platelet deficiencies due to amyloidosis, autoimmune disorder, or medication, etc need to be excluded.

The laboratory platelet testing starts with a platelet count, platelet indices, and morphologic examination. The most important platelet indice is mean platelet volume (MPV), which helps to group platelet disorders into 3 major groups:
The small platelets when MPV <5fL, is pathognomonic for Wiskott-Aldrich syndrome (WAS) and its milder form X-linked macrothrombocytopenia.

The large platelets with MPV >9 to10 fl, is typical for so-called giant platelet diseases which include Bernard-Soulier syndrome(BSS), Glanzmann thrombasthenia(GT), Gray platelet syndrome(GP), MYH9-related platelet disorders, platelet type von Willebrand disease(VWD), white platelet syndrome and alpha-delta granule deficiency.

The remaining platelet disorders have normal sized platelets such as ADP, collagen receptor deficiencies, or Hermansky-Pudlak syndrome(HPS). Our patient will fall into the Hermansky-Pudlak group of large platelet group since her MPV was elevated.

Laboratory Systemic Approach

 


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