DOI 10.1515/cclm-2014-0131 Clin Chem Lab Med 2014; 52(8): 1091–1106 Review Cecilia Carubbia, Elena Massellia, Antonio Nouvenne, Domenico Russo, Daniela Galli, Prisco Mirandola, Giuliana Gobbi* and Marco Vitale* Laboratory diagnostics of inherited platelet disorders Abstract: Inherited platelet disorders (IPDs) are the gen- Introduction eral and common denomination of a broad number of different rare and congenital pathologies affecting plate- Inherited platelet disorders (IPDs) are rare, congenital dis- lets. Even if these disorders are characterized by widely eases of platelet number and/or function characterized by a heterogeneous clinical presentations, all of them are com- widely heterogeneous clinical presentation and a challeng- monly present as defects in hemostasis. Platelet num- ing diagnostic work-up. They usually present as primary ber and/or function are affected by a wide spectrum of hemostatic defects that may range from a prolonged bleed- severity. IPDs might be associated with defects in bone ing after trauma or surgery in adulthood to life-threatening, marrow megakaryocytopoiesis and, rarely, with somatic spontaneous hemorrhages (gastrointestinal, genitourinary defects. Although in the last few years new insights in the or even intracranial) occurring early in life [1, 2]. genetic bases and pathophysiology of IPDs have greatly Defects in platelet function are frequently accom- improved our knowledge of these disorders, much effort panied by abnormalities in bone marrow megakaryocy- still needs to be made in the field of laboratory diagnosis. topoiesis, resulting in reduced platelet counts and altered This review discusses the laboratory approach for the dif- platelet morphology. ferential diagnosis of the most common IPDs, suggesting a In some cases, platelet disorders are associated with common multistep flowchart model which starts from the somatic defects, such as reduced or delayed pigmentation simpler test (platelet count) ending with the more selec- Hermansky-Pudlak syndrome (HPS), hearing loss, renal tive and sophisticated analyses. impairment and/or cataracts (MYH9-related diseases), eczema and susceptibility to infections Wiskott-Aldrich Keywords: bleeding; laboratory tests; platelets; rare syndrome (WAS), limb abnormalities (thrombocytopenias diseases. associated with skeletal defects). While the process of IPDs characterization significantly aCecilia Carubbi and Elena Masselli contributed equally to this work. contributed to our understanding of the genetic bases of *Corresponding authors: Giuliana Gobbi, PhD, Department of megakaryocytopoiesis and platelet function, unfortunately Biomedical, Biotechnological and Translational Sciences (S.Bi. little progress has been made in the field of laboratory diag- Bi.T.), University of Parma, Ospedale Maggiore, Via Gramsci, 14, nostics of these diseases. In fact, diagnosis of the majority 43100 Parma, Italy, Phone: +39 0521 033142, Fax: +39 0521 033033, E-mail: [email protected]; Marco Vitale, MD, Department of IPDs still primarily relies on personal and family history, of Biomedical, Biotechnological and Translational Sciences (S.Bi. co-morbidities (i.e., skeletal defects), peripheral blood Bi.T.), University of Parma, Ospedale Maggiore, Via Gramsci, 14, smear analysis and genetic testing, when available [3, 4]. 43100 Parma, Italy, Phone: +39 0521 033032, This review will discuss the diagnostic algorithm – Fax: +39 0521 033033, E-mail: [email protected] focusing on laboratory tests – for the most common IPDs; Cecilia Carubbi, Elena Masselli, Daniela Galli and Prisco Mirandola: diseases are presented on the basis of their involvement of Department of Biomedical, Biotechnological and Translational Sciences (S.Bi.Bi.T.), Anatomy and Histology Unit, University of platelet count, function, or both. Parma, Ospedale Maggiore, Parma, Italy Antonio Nouvenne: Department of Clinical and Experimental Medicine, University of Parma, Ospedale Maggiore, Parma, Italy Disorders of platelet number Domenico Russo: Unit of Blood Diseases and Cell Therapies, University of Brescia, AO Spedali Civili Brescia, Brescia, Italy This group encompasses MYH9-related disorders, con- genital amegakaryocytic thrombocytopenia (CAMT), 1092 Carubbi et al.: Inherited platelet disorders diagnosis thrombocytopenias associated with skeletal defects, Platelet count is usually below 50 × 109/L and their size is X-linked thrombocytopenia (XLT) with dyserythropoiesis, normal [10]. familial platelet disorders with predisposition to acute Bone marrow aspirate reveals marked megakaryo- leukemia (FDP/AML), benign mediterranean macrothrom- cytic hypoplasia that may progress to bone marrow bocyopenia (BBM), familial thrombocytopenia 2 (THC2). failure. Mutations of the thrombopoietin (TPO) recep- Genetic analysis is the sole specific laboratory test for tor (c-mpl) underlie this disease and can be detected by these IPDs and is currently clinically available for CAMT, genetic testing [11]. thrombocytopenia with absent radii (TAR), thrombocyto- penia with radio-ulnar synostosis (ATRUS), XLT with dys- erythropoiesis and FDP/AML [5] (Table 1). Thrombocytopenias associated with skeletal Beyond genetic testing, diagnosis is essentially based defects on family history (usually relevant in autosomal domi- nant disorders such as MYH9-related disorders, ATRUS, This group of IPDs encompasses three different thrombo- Di George/Velocardiofacial syndrome (VCFS), thrombo- cytopenias associated with peculiar skeletal defects: TAR, cythopenia with predisposition to leukemia, BBM, THC ATRUS and Di George/VCFS. 2) and presence of patognomonic-associated defects TAR is an autosomal recessive disease that manifests affecting other organs (see Figures 1 and 2). During the early in life with a bleeding diathesis that tends to amelio- laboratory diagnostic work-up, a key role is detained by rate with time due to a progressive increase of the platelet peripheral blood smear analysis for platelet morphology count. Diagnosis is straightforward given the presence (i.e., presence of macrothrombocytes – as in the case of of the typical bilateral radial anomalies that affect TAR MYH9-related disorders and BMM – or detection of spin- patients. Bone marrow megakaryocytes are reduced, but dle-shaped Döhle leukocyte inclusions, as in the case of platelet size and function are normal. Defects in the TPO/ MHY9-related diseases) [6]. c-mpl signaling may be found with appropriate genetic tests [12]. ATRUS is an autosomal dominant amegakaryocitic MYH9-related disorders thrombocytopenia associated with aplastic anemia, radio-ulnar synostosis, clinodactyly, syndactyly, hip- This term indicates a group of autosomal dominant dysplasia and sensorineural hearing loss. Like TAR, thrombocytopenias (May-Hegglin anomaly, Sebastian also ATRUS presents with severe thrombocytopenia Syndrome, Fechtner Syndrome and Epstein syndrome) at birth that may improve with time [13]. Detection of caused by mutations within the MYH9 gene, encoding for mutations of HOXA11, a member of the homeobox genes the non-muscle myosin IIA heavy chain which is part of encoding for proteins that detain a central role in skel- the contractile cytoskeleton of megakaryocytes, platelets etal development and hematopoiesis, allows final diag- and neutrophils [7, 8]. nosis [14]. As a result, bone marrow megakaryocitopoiesis is Di George/VCFS is an autosomal dominant macro- ineffective and platelets display abnormally larger dimen- thrombocytopenia typified by cardiac abnormalities, cleft sions (macrothrombocytes). Platelet aggregation tests palate, thymic aplasia, mental retardation, disimmunity. are normal. Thrombocytopenia ranges from 20 × 109/L to The gene involved, usually with a hemizygous loss of 130 × 109/L, but bleeding phenotype is usually mild. Diag- allele, is GP1BB, located at 22q11, one of the three genes nosis is suggested by peculiar co-morbidities, such as sen- defective in Bernard-Soulier syndrome (BSS). Thus, clini- sorineural hearing loss, cataracts, glomerulonephritis, cal manifestations are usually mild and may overlap with but definitive identification of this IPD requires the dem- heterozygous BSS. Again, clinical diagnosis is suggested onstration of a causative mutation within MHY9 [9]. by the relevant co-morbidities and requires confirmation by genetic testing [15]. Congenital amegakaryocytic thrombocyto- penia (CAMT) X-linked thrombocytopenia with dyserythropoiesis CAMT is an autosomal recessive disorder characterized by symptomatic thrombocytopenia manifesting early This X-linked platelet disorder is due to mutations of the in life, occasionally with a severe bleeding phenotype. GATA1 gene, encoding for the transcription factor GATA1, Carubbi et al.: Inherited platelet disorders diagnosis 1093 Table 1 Classification of inherited platelet disorders and laboratory tests currently available. Gene (location) Inheritance Genetic testing Lab test(s) clinically available MYH9-related disorders MYH9 (22q12-13) AD Yes PLT count Peripheral blood smear Platelet aggregometry Congenital amegakaryocytic c-MPL (1p34) AR Yes PLT count thrombocytopenia Peripheral blood smear Bone marrow aspirate Thrombocytopenias associated Y19 (1q21.1), HOXA11 (7p15-p14.2), AD/AR Yes PLT count with skeletal defects GPIBB (22q11) (Bone marrow aspirate) X-linked thrombocytopenia with GATA1 (Xp11.23) X-linked Yes PLT count dyserythropoiesis Peripheral blood smear Bone marrow aspirate Familial platelet disorders with RUNX1 (21q22) AD Yes PLT count predisposition to leukemia Peripheral