Pancytopenia and bone marrow failure

A child or young adult with cytopenias in two or three lineages (low hemoglobin, low platelets, low absolute neutrophil count) without a clear acquired cause. Sometimes the first cytopenia is isolated (Diamond-Blackfan with pure red-cell aplasia; severe congenital neutropenia with isolated neutropenia; thrombocytopenia in some), and the others follow over months to years. The diagnostic decision is whether this is inherited bone marrow failure (IBMF) or acquired aplastic anemia / myelodysplasia. The split matters because inherited disease changes transplant conditioning, family counseling, and surveillance.

Three features point toward an inherited cause and away from acquired aplastic anemia:

1. Personal or family history of congenital anomalies (radial ray defects, short stature, café-au-lait macules, nail and skin findings, exocrine pancreatic insufficiency, thumb anomalies).
2. Macrocytosis disproportionate to the anemia, persistent fetal hemoglobin, or other red-cell dysplasia.
3. Family history of cancer at young ages, sibling early death, or known IBMF in relatives.

A child with isolated severe aplastic anemia and a normal exam can still have an inherited syndrome (Fanconi anemia and dyskeratosis congenita both present without classical features in a meaningful fraction). The chromosome breakage test (Fanconi) and telomere length flow-FISH (dyskeratosis) are the screening tests that catch the cryptic cases.

Pan-cytopenic inherited marrow failure

• Fanconi anemia (FA) (~20 FANC genes; mostly AR, FANCB X-linked): the classic triad is bone marrow failure + congenital anomalies + cancer predisposition. Anomalies include radial ray (absent or hypoplastic thumb), short stature, café-au-lait macules, microphthalmia, microcephaly, renal anomalies, ear abnormalities, abnormal genitalia. Up to 25-40% of FA patients have no classical anomalies, so the chromosome breakage assay (DEB or mitomycin C) is the diagnostic screen for any unexplained marrow failure in a child or young adult. AML and squamous cell carcinoma (head and neck, vulva) are the dominant cancers.
• Dyskeratosis congenita (DC) (telomere maintenance genes: DKC1 X-linked, TERC AD, TERT AD/AR, TINF2 AD, NHP2, NOP10, WRAP53, RTEL1, CTC1, ACD, POT1, PARN): the classic triad is dystrophic nails + lacy reticular skin pigmentation + oral leukoplakia. Pulmonary fibrosis and liver disease are common in adults. The screen is telomere length flow-FISH on peripheral blood lymphocyte subsets (very short, below the 1st percentile, in multiple subsets). Severe early-onset forms (Hoyeraal-Hreidarsson, Revesz, Coats plus) include cerebellar hypoplasia, retinopathy, intracranial calcifications.

Lineage-restricted or syndrome-defining marrow failure

• Shwachman-Diamond syndrome (SDS) (SBDS AR; rarely DNAJC21, EFL1, SRP54): exocrine pancreatic insufficiency + neutropenia + skeletal abnormalities (metaphyseal dysostosis). Second most common cause of pancreatic insufficiency in childhood after cystic fibrosis. Progresses to pan-cytopenia and MDS/AML in a subset.
• Diamond-Blackfan anemia (DBA) (ribosomopathies: RPS19 most common, RPL5, RPL11, RPS26, others; ~AD): pure red-cell aplasia in the first year of life + macrocytosis + elevated fetal hemoglobin + erythrocyte adenosine deaminase + congenital anomalies (thumb anomalies including triphalangeal thumb, short stature, craniofacial features, urogenital anomalies). About 25% have classic Cathie facies.
• Severe congenital neutropenia (SCN) (ELANE AD, HAX1 AR, G6PC3, WAS X-linked, GFI1, CSF3R, JAGN1): recurrent bacterial infections from the first months, profound neutropenia. G-CSF responsive in most. Long-term MDS/AML risk.
• Thrombocytopenia syndromes: congenital amegakaryocytic thrombocytopenia (CAMT; MPL), thrombocytopenia with absent radii (TAR; RBM8A), MYH9-related disorders.

MDS / AML predisposition genes (often present before frank marrow failure)

• GATA2 deficiency: monocytopenia + MonoMAC syndrome (atypical mycobacteria, papillomavirus) + dendritic cell deficiency + MDS/AML.
• RUNX1: familial platelet disorder with predisposition to MDS/AML; mild thrombocytopenia + platelet function defects.
• ANKRD26, ETV6: familial thrombocytopenia with leukemia predisposition.
• DDX41: familial AML/MDS in adults.

Acquired causes to exclude

• Acquired aplastic anemia (idiopathic, autoimmune; treat with immunosuppression or transplant).
• Myelodysplastic syndrome / leukemia.
• Drugs and toxins: chloramphenicol, sulfonamides, benzene, chemotherapy.
• Viral: parvovirus B19 (transient pure red-cell aplasia, severe in chronic hemolysis or immunocompromise), EBV, HIV, hepatitis (seronegative hepatitis-associated aplasia).
• Nutritional: B12, folate, copper deficiency.
• Paroxysmal nocturnal hemoglobinuria (acquired clonal disorder; flow cytometry for GPI-anchored proteins).

1. CBC + reticulocyte count + peripheral blood smear: confirm cytopenias and lineages affected; look for dysplasia, blasts, macrocytosis.
2. MCV and fetal hemoglobin (HbF): macrocytosis + elevated HbF + elevated erythrocyte adenosine deaminase in DBA; macrocytosis common in IBMF generally.
3. Bone marrow aspirate and biopsy with cytogenetics: cellularity, dysplasia, clonal cytogenetic abnormalities (monosomy 7 a red flag).
4. Chromosome breakage assay (DEB or MMC) on peripheral blood lymphocytes: the screen for Fanconi anemia. Should be done in any unexplained marrow failure in any age group before any transplant conditioning is planned.
5. Telomere length flow-FISH on peripheral blood lymphocytes: very short (< 1st percentile) in multiple subsets supports dyskeratosis congenita.
6. Inherited bone marrow failure / MDS predisposition gene panel (germline DNA from non-blood source if possible; saliva or cultured skin fibroblasts to avoid somatic mosaicism in blood).
7. Detailed family history: three generations, cancers at young ages, unexplained deaths, transplants, fibrosis/cirrhosis, MDS/leukemia.
8. Targeted secondary tests as indicated: stool elastase or 72-hour fecal fat (SDS), erythrocyte adenosine deaminase (DBA), skeletal survey (FA, DBA, SDS), renal ultrasound (FA), pulmonary function tests and liver function (DC), HIV/parvovirus/EBV serologies, PNH flow cytometry, B12/folate/copper levels.