Labs

• Platelet count: 60 x 103/mm3 (60 x 109/L) (normal 140-440 x 103/mm3 [140-440 x 109/L])

• Hemoglobin 12. 5 g/dL (125 g/L or 7.75 mmol/L) (normal 13.8-17.2 g/dL or 138-172 g/L or 8.6-10.7 mmol/L)

• Bleeding time 8 minutes (normal 3-7 minutes)

Given this additional information, is this patient's presentation consistent with ITP? What is the likely etiology of this patient's ITP? Identify your treatment goals for this patient.

General Approach to Treatment

O The treatment of ITP is determined by the symptom severity (Table 6-9). In some cases, no therapy is needed. The initial treatment of children with ITP is controversial because 30% to 70% of cases resolve spontaneously irrespective of pharmacologic intervention. Currently, therapy is indicated in children with platelet counts less thaln 10 to 20 x 103 mm3 (10-2 0 * 10 9/L) because most intracranial hemorrhages occur when platelets are in this range.30 In adults, treatment is indicated when platelet counts are less than 20 to 30 x 107mm3 (20-30 x 107L) or less than 50 x 107mm3 (5 0*10

9 31

/L) with serious bleeding or risk factors for bleeding.

Table 67-9 Guidelines for the Initial Management of ITP

30-50 x 10J platelets/nnnn3 Prednisone (1 mg/kg/day) or no piateíeís/nnm - GO x 10VL} Anii-D imnnune globulin mcg/kg}

Nonpharmacologic Therapy

In adults, splenectomy is generally considered after 3 to 6 months if the patient continues to require 10 to 20 mg/day of prednisone to maintain the platelet count greater than 30 x 103/mm3 30 x 109/L) or within 6 weeks ofdiagnosis in nonbleeding patients with platelet counts of less than 10 x 103/mm3 (10 x 109/L) despite treatment. Sple-nectomy may also be considered for urgent treatment of neurologic symptoms or for managing relapse despite an adequate trial of corticosteroids, intravenous immuno-globulin (IVIg), or anti-Rh(D). Even though individual patient response cannot be predicted, approximately two-thirds of refractory adult patients have a favorable response to splenectomy within several days; however, 30% to 40% will have no response or will experience a relapse some time after splenectomy. In children, splenectomy is usually reserved due to the self-limited nature of ITP and fear of infectious complications of splenectomy. Splenectomy is recommended in children with ITP duration greater than one year with significant bleeding symptoms and platelet counts less than 10 x 103/mm3 (10 x 109/L), or platelet counts 10 to 30 x 103/mm3 (10-30 x 109/L) with bleeding symptoms. Between 70% and 80% of children attain complete remission following splenectomy. Laproscopic splenectomy is preferable to open splenectomy because it speeds the recovery and shortens the duration of hospitalization. The major drawback of splenectomy is bacterial sepsis, occurring at incidence rates of approximately 1%. Immunization with Haemophilus influenzae type b, pneumococcal, and meningiococcal vaccines is indicated in all patients two weeks prior to splenec-

tomy.29

Pharmacologic Therapy

The general approach to initial management of ITP is summarized in Table 67-9. Glucocorticoids

Glucocorticoids may decrease splenic sequestration of antibody-coated platelets, diminish antibody generation by the spleen and the bone marrow, and increase platelet output by the bone marrow. In adults, the response rate to oral prednisone (1-1.5 mg/ kg/day) is 50% to 75% with patients usually responding within the first three weeks. In children, severe life-threatening bleeding is treated with either high-dose oral (4-8 mg/kg/day prednisone) or parenteral (30 mg/kg/day methylprednisolone) glucocortic-oids.

IV Immunoglobulin (IVIg)

IVIg impairs the clearance of platelets coated with IgG by activating inhibitory receptor FcRylIb. It is generally indicated in emergencies, during pregnancy, and in chronic management of patients refractory to other treatment options. Roughly 80% of adults will respond to IVIg (1 g/kg/day for 2-3 days), but remission usually is not sustained. In adults, use of IVIg is reserved for severe life-threatening bleeding, platelet counts less than 5 x 103/mm3 (5 x 109/L), with extensive purpura. If treatment is indicated in children, a single dose of IVIg (0.8 g/kg) is usually effective, although other dosing regimens can also be used (1 g/kg x 1 day; 2 g/kg total dose over 2-5 days). IVIg use is complicated by many serious adverse effects and high cost.

Anti-Rh(D)

Anti-Rh(D) can be used only in Rh(D)-positive patients. It is as efficacious as IVIg and is generally less expensive. The indications for use of anti-Rh(D) are identical to those for IVIg. Anti-Rh(D) is desirable form of treatment in chronic ITP when the goal is to circumvent long-term exposure to corticosteroids. At doses of 25 to 75 mcg/kg/ day, anti-Rh(D) may increase the platelet count in about 70% to 80% of children with acute and chronic ITP. Response to anti-Rh(D) lasts about 3 to 5 weeks, and substantial numbers of patients treated repetitively with Rh(D) can postpone or avoid splen-ectomy

Immunosuppressants

Immunosuppressant therapy is generally utilized for patients with platelet counts below 20 x 103/mm3 (20 x 10 /L) who are refractory to or intolerant of all other ITP treatments. Azathioprine and cyclophosphamide produce response rates of 20% to 40% in adult patients who are treated for 2 to 6 months. Other medications used in ITP include vincristine, vinblastine, cyclosporine, and rituximab; due to major toxicities, their use is reserved for refractory ITP.

Thrombopoietic Growth Factors

New treatment options for ITP include a novel thrombopoiesis-stimulating protein and a small-molecule thrombopoietin (TPO) receptor agonist. These agents stimulate the bone marrow to make enough platelets to overcome the body's premature destruction of platelets. Romiplostim and eltrombopag are two new therapeutic agents that have been recently approved by the FDA for the treatment of thrombocytopenia in patients with chronic ITP who have had an insufficient response to corticosteroids, immuno-globulins, or splenectomy.

Romiplostim is a TPO peptide mimetic that binds to and activates the human TPO receptor. As a once weekly subcutaneous injection, romiplostim stimulates mega karyo-poiesis resulting in enhanced platelet production. Initial dose of romiplostim is based on the actual body weight, adjusted weekly by increments of 1 mcg/kg until a maximum of 10 mcg/kg the patient achieves a platelet count greater than or equal to 50 x 107mmJ (50

x 10 /L) as necessary to reduce the risk for bleeding. In clinical studies, most patients who responded to romiplostim achieved and maintained plate-

let counts greater than or equal to 50 x 10 /mm (50 x 10 /L) with a median dose of 2 mcg/kg. Both agents need to be discontinued if platelet counts do not increase after 4 weeks at a maximum dose. Eltrombopag is a once-daily oral nonpeptide thrombopoi-etin receptor agonist with a low immunogenic potential that stimulates megakaryocyte proliferation and differentiation.

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