6.4 Immune Thrombocytopenia, Aplastic Anemia, and Bone Marrow Failure

Not every low blood count in a hematology clinic is leukemia. CPHON still expects you to sort three nonmalignant marrow stories: immune thrombocytopenia (ITP), acquired aplastic anemia, and inherited bone marrow failure. A well toddler covered in petechiae after a viral illness is a different protocol from a pale school-age child with pancytopenia and a hypocellular marrow, and both are different from a child with abnormal thumbs whose DNA cannot repair crosslinks.

ITP: post-viral toddlers, dry versus wet, and when not to transfuse

Childhood ITP often follows a viral illness in a toddler or preschooler. The child looks well. The platelet count may be under 10,000/µL. Exam shows petechiae and purpura. The marrow, if examined, shows megakaryocytes; this is peripheral immune destruction, not a production failure. Isolated thrombocytopenia without blasts, without anemia or neutropenia of marrow failure, and without a sick, leukemic-looking child is the classic picture. Any doubt about leukemia still needs a hematology workup; ITP is a diagnosis of a well child with a compatible CBC, not a guess in a febrile infant with a mediastinal mass.

Dry purpura is skin only—petechiae and bruises. Wet purpura is mucosal bleeding: oral blood blisters, active epistaxis, hematuria, or gastrointestinal blood. Wet bleeding raises concern for serious hemorrhage, including intracranial hemorrhage, and usually tips the team from observation to treatment. A playful 2-year-old with dry petechiae and platelets of 9,000/µL may be observed with activity counseling (no trampolines, helmets for bikes, head-injury instructions). A child with wet oral blisters, or any neurologic change, is treated.

First-line options when treatment is indicated include intravenous immunoglobulin (IVIG), which often raises platelets within a day or two, and corticosteroids. Anti-D immunoglobulin can be used in Rh-positive children who still have a spleen; it coats red cells and distracts the spleen, so hemolysis is an expected risk—watch hemoglobin, not only platelets. Anti-D is not used after splenectomy. For chronic ITP, thrombopoietin-receptor agonists such as eltrombopag or romiplostim stimulate production; they are not first-dose emergency drugs for a new toddler with dry purpura.

Avoid platelet transfusion unless bleeding is life-threatening (for example, intracranial hemorrhage). Transfused platelets are consumed by the same antibody and do not provide lasting counts; they still have a role when a child is actively, dangerously bleeding, given together with IVIG or steroids, not as routine “keep the count above 50” floor practice.

Acquired aplastic anemia: empty marrow, transplant versus IST

Acquired aplastic anemia presents with pancytopenia—anemia, neutropenia, and thrombocytopenia—and a hypocellular marrow without leukemic blasts or dysplasia that would shift the diagnosis toward myelodysplasia or marrow replacement. Bruising, pallor, and mouth ulcers or fever from neutropenia appear together. This is not ITP. Platelets alone do not explain the low neutrophils and hemoglobin.

In children with severe aplastic anemia, matched-sibling hematopoietic stem cell transplant is preferred first-line therapy when a fully matched sibling donor is available, because it can restore hematopoiesis more durably than immunosuppression alone. When transplant is not the first path (no matched sibling, or protocol timing), immunosuppressive therapy (IST) classically uses horse antithymocyte globulin (ATG) plus cyclosporine. Supportive care is not optional while those decisions proceed: irradiated, leukoreduced transfusions as indicated, fever pathways, and central-line infection prevention. G-CSF is not a cure for aplastic anemia; it may appear in selected neutropenia support but does not replace ATG, cyclosporine, or transplant.

A 9-year-old with new pancytopenia, no dysmorphic features, and a hypocellular marrow needs HLA typing of siblings quickly, not months of “watchful ITP observation.” Horse ATG infusion nursing includes anaphylaxis and serum-sickness vigilance; cyclosporine adds therapeutic-level and renal monitoring.

Inherited bone marrow failure: four names you must separate

Inherited syndromes cause marrow failure plus extra-hematopoietic clues. They also raise myelodysplasia and solid-tumor risk, and they change how you would ever give chemotherapy.

Fanconi anemia is a DNA-crosslink-repair disorder. A 4-year-old with short stature, abnormal thumbs, café-au-lait spots, and pancytopenia is Fanconi until the chromosomal-breakage or genetic test says otherwise. Because cells cannot repair DNA damage, chemotherapy and radiation are unusually toxic—dose modifications are mandatory if malignancy treatment is ever required. Do not treat Fanconi as “ordinary” aplastic anemia with a full-intensity leukemia induction if blasts appear; that is a toxicity disaster.

Diamond-Blackfan anemia is pure red-cell aplasia: hemoglobin and reticulocytes crash; neutrophils and platelets are typically spared at presentation. Corticosteroids are first-line for many children; nonresponders enter a chronic transfusion (and iron) program, with HSCT for selected patients. It is not a pancreatic disease and not a pure platelet disorder.

Shwachman-Diamond syndrome pairs neutropenia with exocrine pancreatic insufficiency and skeletal findings. Steatorrhea and failure to thrive plus recurrent bacterial infection should pull pancreatic enzymes into the same conversation as G-CSF. Dyskeratosis congenita is a telomere biology disorder. The classic mucocutaneous triad (nails, leukoplakia, lacy or abnormal skin pigment) may be incomplete in children; pulmonary fibrosis and cancer risk still belong in teaching.

G-CSF, infection precautions, and the exam’s sorting test

Granulocyte colony-stimulating factor (G-CSF, filgrastim) is used in selected inherited or chronic neutropenias (severe congenital neutropenia, and in Shwachman-Diamond as indicated) to raise neutrophils and cut infection. It does not treat ITP, does not replace factor in hemophilia, and does not empty iron from a thalassemia liver. Fever in a child with aplastic anemia or inherited neutropenia is an infectious emergency: prompt evaluation, broad antibiotics per protocol, no rectal temperatures or rectal medications, careful mouth care, and visitor/crowd teaching during profound neutropenia. Live vaccines follow immunology guidance, not a school fair calendar.

Sort at the door. Isolated platelets in a well toddler: ITP, dry versus wet, observe or IVIG/steroids/anti-D, platelets only if life-threatening. Pancytopenia and empty marrow: aplastic anemia, sibling transplant versus horse ATG plus cyclosporine. Malformations plus failure: name the inherited syndrome before anyone writes a full-dose alkylator.