Symptoms usually present from the period of birth to early childhood as: nose bleeds, bruising, and/or gum bleeding. Problems later in life may arise from anything that can cause internal bleeding such as: stomach ulcers, surgery, trauma, or menstruation. Abnormality of the abdomen, Epistaxis, Menorrhagia, Purpura, Thrombocytopenia, and prolonged bleeding time have also been listed as symptoms of various Giant Platelet Disorders.

Giant platelet disorders can be further categorized:

- caused by auto-immune disorders, for example Immune thrombocytopenic purpura (ITP), and characterized by low platelet count, but high MPV (Mean-Platelet Volume).

- Caused by glycoprotein abnormalities: Bernard-Soulier syndrome, Velocardiofacial syndrome

- Caused by calpain defect: Montreal platelet syndrome

- Caused by alpha granules defect: Gray platelet syndrome

- Characterized by abnormal neutrophil inclusions: May-Hegglin anomaly, Sebastian syndrome

- With systemic manifestations: Hereditary macrothrombocytopenia with hearing loss, Epstein syndrome, Fechtner syndrome

- With no specific abnormalities: Mediterranean macrothrombocytopenia

- Harris platelet syndrome

Characteristically, there is increased mucosal bleeding:

- menorrhagia

- easy bruising

- epistaxis

- gingival bleeding

- gastrointestinal bleeding

- postpartum bleeding

- increased bleeding post-operatively.

The bleeding tendency is variable but may be severe. Hemarthrosis, particularly spontaneous, is very rare, in contrast to the hemophilias.

Platelet numbers and morphology are normal. Platelet aggregation is normal with ristocetin, but impaired with other agonists such as ADP, thrombin, collagen or epinephrine.

Glanzmann's thrombasthenia is an abnormality of the platelets. It is an extremely rare coagulopathy (bleeding disorder due to a blood abnormality), in which the platelets contain defective or low levels of glycoprotein IIb/IIIa (GpIIb/IIIa), which is a receptor for fibrinogen. As a result, no fibrinogen bridging of platelets to other platelets can occur, and the bleeding time is significantly prolonged.

Bernard–Soulier syndrome often presents as a bleeding disorder with symptoms of:

HPS was identified among healthy blood donors in the north-eastern part of the Indian subcontinent, characterized by absent bleeding symptoms, mild to severe thrombocytopenia (platelets rarely <50 X 109/L)with giant platelets (Mean platelet volume 10fL) and normal platelet aggregation studies with absent MYH9 mutation.

In the blood donors with HPS authors found a statistically higher MPV, RDW and a lower platelet count and platelet biomass.

At present the diagnosis of HPS is made by ascertaining the ethnicity of the patient, as well as assessing for conditions causing acquired thrombocytopenias, and after also excluding the known inherited giant platelet disorders(IGPD) and other congenital thrombocytopenias. Unfortunately some patients with IGPD are treated inappropriately with corticosteroids, immunoglobulin infusions and even splenectomy.

It is extremely important to recognize Harris platelet syndrome, as one third the population of certain parts of Indian subcontinent is affected.

Harris platelet syndrome (HPS) is the most common inherited giant platelet disorder.

Most people with ET are without symptoms referable to ET at the time of diagnosis, which is usually ultimately made after noting an elevated platelet level on a routine complete blood count (CBC). The most common symptoms are bleeding (due to dysfunctional platelets), blood clots (e.g., deep vein thrombosis or pulmonary embolism), headache, nausea, vomiting, abdominal pain, visual disturbances, dizziness, fainting, and numbness in the extremities; the most common signs are increased white blood cell count, reduced red blood cell count, and an enlarged spleen.

The various types of vWD present with varying degrees of bleeding tendency, usually in the form of easy bruising, nosebleeds, and bleeding gums. Women may experience heavy menstrual periods and blood loss during childbirth.

Severe internal bleeding and bleeding into joints are uncommon in all but the most severe type, vWD type 3.

Many cases of congenital dysfibrinogenemia are asymptomatic. Since manifestations of the disorder generally occur in early adulthood or middle-age, younger individuals with a gene mutation causing it may not have had time to develop symptoms while previously asymptomatic individuals of advanced age with such a mutation are unlikely to develop symptoms. Bleeding episodes in most cases of this disorder are mild and commonly involve easy bruising and menorrhagia. Less common manifestations of bleeding may be severe or even life-threatening; these include excessive bleeding after tooth extraction, surgery, vaginal birth, and miscarriage. Rarely, these individuals may suffer hemarthrosis or cerebral hemorrhage. In one study of 37 individuals >50 years old afflicted with this disorder, 19% had a history of thrombosis. Thrombotic complications occur in both arteries and veins and include transient ischemic attack, ischemic stroke, myocardial infarction, retinal artery thrombosis, peripheral artery thrombosis, and deep vein thrombosis. In one series of 33 individuals with a history of thrombosis due to congenital dysfibrinogenemia, five developed chronic pulmonary hypertension due to ongoing pulmonary embolism probably stemming form deep vein thrombosis. About 26% of individuals with the disorder suffer both bleeding and thrombosis complications.

X-linked thrombocytopenia is typically diagnosed in infancy. The disease presents as a bleeding disorder with easy bruising, mucosal bleeding, such as nosebleeds, and mild to severe anemia. Anemia is a condition in which there is an insufficient number of red blood cells to carry adequate levels of oxygen to the body’s tissues. X-linked thrombocytopenia is considered to be the milder phenotype of the "WAS"-related disorders. As age increases, the severity of symptoms tends to decrease. However, individuals with X-linked thrombocytopenia have an increased risk for life-threatening brain hemorrhages and spontaneous bleeding.

Essential thrombocythemia (ET) is a rare chronic blood condition characterised by the overproduction of platelets by megakaryocytes in the bone marrow. It may, albeit rarely, develop into acute myeloid leukemia or myelofibrosis. It is one of four myeloproliferative neoplasms (blood cancers that occur when the body makes too many white or red blood cells, or platelets).

The differential diagnosis for Bernard–Soulier syndrome includes both Glanzmann thrombasthenia and pediatric Von Willebrand disease. BSS platelets do not aggregate to ristocetin, and this defect is not corrected by the addition of normal plasma, distinguishing it from von Willebrand disease.

Type 1 vWD (60-80% of all vWD cases) is a quantitative defect which is heterozygous for the defective gene. It can arise from failure to secrete vWF into the circulation or from vWF being cleared more quickly than normal. Decreased levels of vWF are detected at 20-50% of normal, i.e. 20-50 IU.

Many patients are asymptomatic or may have mild symptoms and not have clearly impaired clotting, which might suggest a bleeding disorder. Often, the discovery of vWD occurs incidentally to other medical procedures requiring a blood work-up. Most cases of type 1 vWD are never diagnosed due to the asymptomatic or mild presentation of type I and most people usually end up leading a normal life free of complications, with many being unaware that they have the disorder.

Trouble may, however, arise in some patients in the form of bleeding following surgery (including dental procedures), noticeable easy bruising, or menorrhagia (heavy menstrual periods). The minority of cases of type 1 may present with severe hemorrhagic symptoms.

The primary manifestations are thrombocytopenia and megakaryocytopenia, or low numbers of platelets and megakaryocytes. There is an absence of megakaryocytes in the bone marrow with no associated physical abnormalities.

Gray platelet syndrome (GPS), or platelet alpha-granule deficiency, is a rare congenital autosomal recessive bleeding disorder caused by a reduction or absence of alpha-granules in blood platelets, and the release of proteins normally contained in these granules into the marrow, causing myelofibrosis.

GPS is primarily inherited in an autosomal recessive manner, and the gene that is mutated in GPS has recently been mapped to chromosome 3p and identified as "NBEAL2". "NBEAL2" encodes a protein containing a BEACH domain that is predicted to be involved in vesicular trafficking. It is expressed in platelets and megakaryocytes and is required for the development of platelet alpha-granules. "NBEAL2" expression is also required for the development of thrombocytes in zebrafish.

GPS is characterized by "thrombocytopenia, and abnormally large agranular platelets in peripheral blood smears." The defect in GPS is the failure of megakaryocytes to package secretory proteins into alpha-granules. Patients with the GPS are affected by mild to moderate bleeding tendencies. Usually these are not major bleeds but there has been some life threatening cases. Also Women will tend to have heavy, irregular periods. Myelofibrosis is a condition that usually comes with the Gray Platelet syndrome.

The cause for this disorder appears to be a mutation in the gene for the TPO receptor, "c-mpl", despite high levels of serum TPO. In addition, there may be abnormalities with the central nervous system including the cerebrum and cerebellum which could cause symptoms.

Thrombocytopenia usually has no symptoms and is picked up on a routine full blood count (or complete blood count). Some individuals with thrombocytopenia may experience external bleeding such as nosebleeds, and/or bleeding gums. Some women may have heavier or longer periods or breakthrough bleeding. Bruising, particularly purpura in the forearms and petechiae in the feet, legs, and mucous membranes, may be caused by spontaneous bleeding under the skin.

Eliciting a full medical history is vital to ensure the low platelet count is not secondary to another disorder. It is also important to ensure that the other blood cell types, such as red blood cells and white blood cells, are not also suppressed.

Painless, round and pinpoint (1 to 3 mm in diameter) petechiae usually appear and fade, and sometimes group to form ecchymoses. Larger than petechiae, ecchymoses are purple, blue or yellow-green areas of skin that vary in size and shape. They can occur anywhere on the body.

A person with this disease may also complain of malaise, fatigue and general weakness (with or without accompanying blood loss). Acquired thrombocytopenia may be associated with a history of drug use. Inspection typically reveals evidence of bleeding (petechiae or ecchymoses), along with slow, continuous bleeding from any injuries or wounds. Adults may have large, blood-filled bullae in the mouth. If the person's platelet count is between 30,000 and 50,000/mm, bruising with minor trauma may be expected; if it is between 15,000 and 30,000/mm, spontaneous bruising will be seen (mostly on the arms and legs).

This condition may involve the alpha granules or the dense granules.

Therefore the following examples include:

- Platelet alpha-granules

- Gray platelet syndrome

- Quebec platelet disorder

- Dense granules

- δ-Storage pool deficiency

- Hermansky–Pudlak syndrome

- Chédiak–Higashi syndrome

Individuals with congenital hypfibringenemia often lack any symptoms are detected by routine lab testing of fibrinogen or when tested for it because close relatives have symptomatic hypofibrinogenmeia. Indeed, studies indicate that, among family members with the identical congenital hypofibrinogenemia mutation, some never exhibit symptoms and those that are symptomatic develop symptoms only as adults.

The presentation of TTP is variable. The initial symptoms, which force the patient to medical care, are often the consequence of lower platelet counts like purpura (present in 90% of patients), ecchymosis and hematoma. Patients may also report signs and symptoms as a result of (microangiopathic) hemolytic anemia, such as (dark) beer-brown urine, (mild) jaundice, fatigue and pallor. Cerebral symptoms of various degree are present in many patients, including headache, paresis, speech disorder, visual problems, seizures and disturbance of consciousness up to coma. The symptoms can fluctuate so that they may only be temporarily present but may reappear again later in the TTP episode. Other unspecific symptoms are general malaise, abdominal, joint and muscle pain. Severe manifestations of heart or lung involvements are rare, although affections are not seldom measurable (such as ECG-changes).

X-linked thrombocytopenia, also referred to as XLT or thrombocytopenia 1, is an inherited clotting disorder that primarily affects males. It is a "WAS"-related disorder, meaning it is caused by a mutation in the Wiskott-Aldrich Syndrome ("WAS") gene, which is located on the short arm of the X chromosome. "WAS"-related disorders include Wiskott-Aldrich syndrome, XLT, and X-linked congenital neutropenia (XLN). Of the "WAS"-related disorders, X-linked thrombocytopenia is considered to be the milder phenotype. Between 1 and 10 per million males worldwide are affected with this disorder. Females may be affected with this disorder but this is very rare since females have two X chromosomes and are therefore typically carriers of the mutation.

The "presentation" (signs/symptoms) of an individual with platelet storage pool deficiency is as follows:

Immune thrombocytopenia (ITP) is a type of thrombocytopenic purpura defined as isolated low platelet count (thrombocytopenia) with normal bone marrow and the absence of other causes of thrombocytopenia. It causes a characteristic purpuric rash and an increased tendency to bleed. Two distinct clinical syndromes manifest as an acute condition in children and a chronic condition in adults. The acute form often follows an infection and has a spontaneous resolution within two months. Chronic immune thrombocytopenia persists longer than six months with a specific cause being unknown.

ITP is an autoimmune disease with antibodies detectable against several platelet surface antigens.

ITP is diagnosed by a low platelet count in a complete blood count (a common blood test). However, since the diagnosis depends on the exclusion of other causes of a low platelet count, additional investigations (such as a bone marrow biopsy) may be necessary in some cases.

In mild cases, only careful observation may be required but very low counts or significant bleeding may prompt treatment with corticosteroids, intravenous immunoglobulin, anti-D immunoglobulin, or immunosuppressive drugs. "Refractory ITP" (not responsive to conventional treatment) may require splenectomy, the surgical removal of the spleen. Platelet transfusions may be used in severe bleeding together with a very low count. Sometimes the body may compensate by making abnormally large platelets.

Increased platelet counts can be due to a number of disease processes:

- Essential (primary)

- Essential thrombocytosis (a form of myeloproliferative disease)

- Other myeloproliferative disorders such as chronic myelogenous leukemia, polycythemia vera, myelofibrosis

- Reactive (secondary)

- Inflammation

- Surgery (which leads to an inflammatory state)

- Hyposplenism (decreased breakdown due to decreased function of the spleen)

- Splenectomy

- Asplenia (absence of normal spleen function)

- Iron deficiency anemia or hemorrhage

Over-medication with drugs that treat thrombocytopenia, such as eltrombopag or romiplostim, may also result in thrombocytosis.

Other causes include the following

- Kawasaki disease

- Soft tissue sarcoma

- Osteosarcoma

- Dermatitis (rarely)

- Inflammatory bowel disease

- Rheumatoid arthritis

- Nephritis

- Nephrotic syndrome

- Bacterial diseases, including pneumonia, sepsis, meningitis, urinary tract infections, and septic arthritis.

The vast majority of causes of thrombocytosis are acquired disorders, but in a few cases, they may be congenital, such as thrombocytosis due to congenital asplenia.