Thrombocytopenia — diagnosing ITP and excluding the dangerous mimics

Diagnosis: immune thrombocytopenia (ITP). Isolated SEVERE thrombocytopenia (platelets 8 x 10^9/L) with normal haemoglobin and white cells, a normal blood film (no schistocytes, no blasts), normal PT and APTT, in an otherwise WELL patient with NO splenomegaly or lymphadenopathy, is the classic presentation of ITP — a diagnosis of exclusion once secondary causes are ruled out.^[1]

Diagnosis of exclusion — the dangerous mimics to actively exclude:^[2]

• TTP — excluded here by the ABSENCE of schistocytes, neurology, renal impairment and fever (TTP needs urgent plasma exchange; never give platelets).
• DIC — excluded by the NORMAL PT, APTT and (implicitly) fibrinogen/D-dimer.
• Acute leukaemia / marrow failure — excluded by the normal haemoglobin, white cells and absence of blasts on the film.
• EDTA pseudothrombocytopenia — excluded by the film confirming true thrombocytopenia (no clumps); a citrate-tube recheck is reasonable if any doubt.

Investigations.^[1]

• Confirm: full blood count, blood film, coagulation screen (PT, APTT, fibrinogen, D-dimer) — all consistent with ITP here.
• Secondary-cause screen in all newly diagnosed adults: HIV and hepatitis C serology, H. pylori testing (urea breath test or stool antigen), antinuclear antibody and anti-dsDNA, beta-HCG, thyroid function, immunoglobulins.
• Bone marrow aspirate and trephine: NOT required routinely in a typical case like this. Reserve for atypical features, age over 60, before splenectomy, or refractory disease.

Immediate management — treat the patient, not the number.^[3]

• The principle is to achieve a SAFE (haemostatic) platelet count, generally over 30, NOT a normal count. With platelets under 10 and active bleeding (gum bleeding, menorrhagia), she needs treatment.
• First-line: oral prednisolone 1 mg/kg/day as a short course with planned taper (about two-thirds respond). High-dose dexamethasone 40 mg daily for 4 days is an alternative pulse.
• Because the count is under 10 and she has active bleeding, add IVIg 0.4 to 1 g/kg/day for a RAPID response (24 to 48 hours). If Rh(D)-positive and non-splenectomised, IV anti-D is an alternative.
• General haemostatic measures: avoid intramuscular injections, NSAIDs and antiplatelets; give tranexamic acid for the menorrhagia/mucosal bleeding; control any hypertension.
• Admit for active bleeding and platelets under 10; she is NOT currently a life-threatening bleed, but if she were (suspected intracranial haemorrhage), give the rescue bundle — IV methylprednisolone + IVIg + platelet transfusion together.

Safety-netting and follow-up.^[3]

• Warn to re-present immediately with severe headache, visual disturbance or heavy bleeding (features of intracranial haemorrhage).
• Plan a taper of steroids to limit toxicity; if chronic, persistent or refractory, escalate to second-line therapy — TPO receptor agonists (eltrombopag, romiplostim), rituximab, splenectomy or fostamatinib.