MBBS viva · Haematology
Thrombocytopenia and immune thrombocytopenia (ITP) — viva
A final-prof viva on thrombocytopenia — classifying by mechanism, establishing the diagnosis of immune thrombocytopenia (ITP) by exclusion, distinguishing ITP from the dangerous mimics (TTP, DIC, HIT) at the bench, and justifying the stepwise management (prednisolone, IVIg, TPO receptor agonists, rituximab, splenectomy) at dose-level detail.
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NEET-PGINICETUSMLEPLAB
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Interpretation
The examiner opens with: "A 26-year-old woman has platelets of 9, widespread bruising and epistaxis. Her haemoglobin and white cells are normal, the blood film is normal apart from large platelets, and her PT and APTT are normal. Talk me through your diagnosis and your management."
- The pattern — isolated severe thrombocytopenia, normal other counts, a normal blood film (no schistocytes, no blasts), normal PT and APTT, and an otherwise well patient with no splenomegaly — is immune thrombocytopenia (ITP), a diagnosis of exclusion once secondary causes are ruled out.[1]
- Confirm by excluding the dangerous mimics (below), screen for secondary causes (HIV, hepatitis C, H. pylori, SLE, pregnancy), and treat with first-line prednisolone plus IVIg for a rapid response given the count under 10.
Key points
The examiner will probe each; defend at viva depth:
- Classification by mechanism — every low platelet count is run through production (marrow failure, leukaemia, chemo, B12/folate), destruction (immune — ITP, SLE, HIV, HCV, drugs; consumptive — TTP, HUS, DIC, HELLP; HIT), sequestration (hypersplenism) and dilutional/spurious (massive transfusion; EDTA clumping).[2]
- The dangerous mimics — distinguish at the bench: ITP has a NORMAL film and coagulation; TTP has SCHISTOCYTES plus neurology/renal/fever and normal coagulation; DIC has prolonged PT and APTT with low fibrinogen and high D-dimer; HIT is a platelet fall 5 to 10 days after heparin with THROMBOSIS (not bleeding) and a normal film.[2]
- ITP pathophysiology — it is NOT just destruction: IgG autoantibodies against GPIIb/IIIa cause splenic phagocytosis, AND cytotoxic T cells/antibodies damage megakaryocytes (impaired production). Thrombopoietin is inappropriately normal — the rationale for TPO receptor agonists. The spleen is both the site of destruction AND a site of antibody production, which is why splenectomy works.[1]
- Treat the patient, not the number — the goal is a SAFE count (over 30), not a normal count; asymptomatic patients over 30 may be observed. First-line: prednisolone 1 mg/kg/day (short course, taper) or dexamethasone 40 mg daily for 4 days; IVIg 0.4 to 1 g/kg/day for rapid response, children, bleeding, pregnancy.[3]
- Second-line therapy — TPO receptor agonists (eltrombopag 50 mg oral daily; romiplostim subcutaneous weekly) stimulate megakaryocyte production and are effective in roughly 80 percent; rituximab 375 mg/m^2 weekly x 4; splenectomy (curative in about two-thirds — vaccinate pre-op); fostamatinib (SYK inhibitor) and rilzabrutinib (BTK inhibitor) for refractory disease.[1]
- The life-threatening bleed / intracranial haemorrhage — give the rescue bundle: IV methylprednisolone + IVIg + platelet transfusion together; platelet transfusion is otherwise avoided in ITP because the platelets are rapidly destroyed.[3]
- TTP is the must-not-miss — thrombocytopenia plus neurology plus renal plus fever plus schistocytes = urgent plasma exchange within 4 to 8 hours; do NOT give platelets (they fuel microvascular thrombosis); do not wait for the ADAMTS13 result.[2]
- Special populations — children: observe if well, usually self-limiting, avoid splenectomy; pregnancy: prefer IVIg and low-dose steroids, avoid TPO-RA and rituximab, watch the neonate for thrombocytopenia; elderly: bleed more at any count, favour earlier TPO-RA.
References
- Provan D, et al. Updated international consensus report on the investigation and management of primary immune thrombocytopenia. Blood Advances 2019.[1]
- Gafter-Gvili A. Current approaches for the diagnosis and management of immune thrombocytopenia. European Journal of Internal Medicine 2023.[2]
- Neunert C, et al. American Society of Hematology 2019 guidelines for immune thrombocytopenia. Blood Advances 2019.[3]
References3ShowHide
- [1]Provan D, Arnold DM, Bussel JB, et al. Updated international consensus report on the investigation and management of primary immune thrombocytopenia. Blood Advances, 2019.PMID 31770441
- [2]Anat GG Current approaches for the diagnosis and management of immune thrombocytopenia. European Journal of Internal Medicine, 2023.PMID 36424271
- [3]Neunert C, Terrell DR, Arnold DM, et al. American Society of Hematology 2019 guidelines for immune thrombocytopenia. Blood Advances, 2019.PMID 31794604