Platelet storage pool deficiency of alpha and delta granules

Angiomatoid Fibrous Histiocytoma With Paraneoplastic Platelet Storage Pool Deficiency

Angiomatoid fibrous histiocytoma is a rare soft tissue tumor usually discovered in young individuals. This tumor is often mistaken for a hematoma and typically misdiagnosed. It is commonly found in the extremities and may be associated with a site of recent or previous trauma. Characteristic histology includes nodules of histiocytoid spindle cells with pseudoangiomatoid spaces, fibrous pseudocapsules, and lymphoid cuffing. We describe the case of an 8-year-old girl who presented after incision and drainage of a superficial thigh lesion and experienced subsequent chronic bleeding of her wound. Her initial presentation was concerning for an underlying bleeding disorder, and laboratory analysis uncovered a paraneoplastic platelet function disorder that resolved with therapy of the primary tumor.

Combined alpha-delta platelet storage pool deficiency is associated with mutations in GFI1B

Combined alpha-delta platelet storage pool deficiency is characterized by the absence or reduction in the number of both alpha granules and dense bodies. This disorder can have variable severity as well as a variable inheritance pattern. We describe two patients from unrelated families with combined alpha-delta storage pool deficiency due to mutations in GFI1B, a zinc finger protein known to act as a transcriptional repressor of various genes. We demonstrate that this disease is associated with either a heterozygous mutation (de novo or familial) abrogating the binding of the zinc fingers with the promoter of its target genes, or by hypomorphic biallelic mutations in GFI1B leading to autosomal recessive inheritance.

Current Strategies in Diagnosis of Inherited Storage Pool Defects

Inherited platelet defects lead to bleeding symptoms of varying severity. Typically, easy bruising, petechiae, epistaxis, and mucocutaneous bleeding are observed in affected patients. The platelet defects are classified into disorders affecting either platelet surface receptors or intracellular organelles of platelets. The latter are represented by platelet storage pool diseases (SPD) which share a defect of platelet granules. Platelet α-granules, δ-granules, or both may be affected resulting in the clinical picture of α-SPD (e.g. Gray platelet syndrome, Quebec platelet disorder, arthrogryposis, renal dysfunction, and cholestasis syndrome), δ-SPD (e.g. Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, Griscelli syndrome), or αδ-SPD (e.g. X-linked thrombocytopenia, Wiskott-Aldrich syndrome). Diagnosis of SPD is very extensive and requires platelet aggregation and flow cytometry analyses with interpretation from a specialist. Many of these disorders share common treatments, however, efficacy can vary between different patients. Therapy regiments with tranexamic acid, DDAVP, activated FVIIa, and platelet transfusions have been published. Stem cell or bone marrow transplantations are preserved for severe defects. Here, we describe the pathophysiology, clinical manifestations, and diagnosis of the major human SPDs.

An inherited macrothrombocytopenic disorder with abnormal large granules

Inherited giant platelet syndromes are a heterogeneous group of rare bleeding disorders. In the current study, a patient was reported with prolonged bleeding time, thrombocytopenia and giant platelets. Both the patient's red and white cell counts were normal without morphological abnormalities. The electron microscopy of platelets showed abnormal large electron-dense granules in the cytoplasm with exocytosis being easily observed. Her fathers platelets had the same abnormalities. The expression of glycoprotein (GP)Ib, GPIIb and GPIIIa on the surface of the patient's platelets was normal, and her platelet aggregation in response to ADP and ristocetin was also normal. Immunogold probes combined to monoclonal antibodies against GPIIIa, P-selectin or CD63 could not identify any relationship between the aberrant structures and alpha granules or lysosomes of platelet. Serotonin level was normal in the platelets of the patient, indicating the electron opaque granules are not dense bodies. The morphological abnormalities of the platelets from the patient are clearly distinguishable from other hereditary giant platelet disorders. We propose that the abnormal large granules from the patient's platelets probably represent a novel inherited thrombocytopenic disorder.

Alpha-delta platelet storage pool deficiency in three generations

Alpha-Delta platelet storage pool deficiency (alphadelta SPD) is a rare inherited bleeding disorder affecting both males and females, occurring in families, as well as sporadically. Patient platelets in most cases are moderately deficient in both alpha granules and dense bodies. Only one patient has been severely deficient in both organelles. The present study is the first to document a severe decrease in both platelet alpha granules and dense bodies in four members in three generations of the same family. Efforts to differentiate this disorder from other hypogranular platelets syndromes in the present investigation suggested that the alpha granules and dense bodies become connected to channels of the open canalicular system (OCS) and lose their contents to the exterior without prior activation of the cells. In contrast, alpha granule formation in the white platelet syndrome is too slow, and cells leave the bone marrow still in the process of producing organelles. Gray platelet syndrome platelets can make alpha granules, but their enclosing membranes are unable to retain stored products. As a result, the organelles lose their contents to surrounding cytoplasm in megakaryocytes and platelets, not selectively through the demarcation system channels and OCS channels. Thus, the pathogenesis of alphadelta SPD is unique.

Molecular defects that affect platelet dense granules

Platelet dense granules form using mechanisms shared by melanosomes in melanocytes and by subsets of lysosomes in more generalized cells. Consequently, disorders of platelet dense granules can reveal how organelles form and move within cells. Models for the study of new vesicle formation include isolated delta-storage pool deficiency, combined alphadelta-storage pool deficiency, Hermansky-Pudlak syndrome (HPS), Chediak-Higashi syndrome, Griscelli syndrome, thrombocytopenia absent radii syndrome, and Wiskott-Aldrich syndrome. The molecular bases of dense granule deficiency are known for the seven subtypes of HPS, as well as for Chediak-Higashi syndrome, Griscelli syndrome, and Wiskott-Aldrich syndrome. The gene products involved in these disorders help elucidate the generalized process of the formation of vesicles from extant membranes such as the Golgi.