Clinical Analysis: Day 10 Neonate, OB Setting, Bilirubin 17.6 mg/dL

The Core Problem: Why is jaundice persisting/worsening at day 10?

Cause 1: UTI/Sepsis-Driven Jaundice (PRIMARY DRIVER)

• Sepsis/infection impairs hepatocyte uptake and conjugation of bilirubin
• Inhibition of glucuronosyltransferase activity
• Hemolysis from endotoxin-mediated red cell damage

Cause 2: Underlying Hemolytic Process - The Blood Film is the Key Finding

• Macrocytes
• Tear drop cells (dacrocytes)
• Anisopoikilocytosis
• Hb 11.3 g/dL (borderline low for day 10 - expected >13 g/dL at birth, may have fallen)
• MFI (Mean Fluorescence Intensity) 792 - this is likely MCV or possibly osmotic fragility data; if MFI = MCV, then 792 fL is not physiologically possible for MCV. More likely this refers to MFI from flow cytometry for osmotic fragility or EMA binding (eosin-5'-maleimide test for hereditary spherocytosis/elliptocytosis), OR it could be reticulocyte MFI.

1. Bone marrow infiltration (extramedullary haematopoiesis is normal in newborns but stress erythropoiesis from infection/hemolysis exaggerates this)
2. Thalassemia - tear drops are classic in beta-thal major/hydrops; alpha-thal trait
3. Myelofibrosis-like picture - very rare in neonates
4. Diamond-Blackfan anaemia - macrocytes + anisopoikilocytosis

• Active haematopoiesis/reticulocytosis (reticulocytes are large) - consistent with hemolytic anaemia
• Folate/B12 deficiency (less likely at day 10)
• Congenital dyserythropoietic anaemia (CDA)
• Hypothyroidism

Differential Diagnosis Summary

The MFI 792 - What Does It Mean?

• If this is EMA-MFI (eosin-5-maleimide binding) from flow cytometry: values <792 relative units (compared to normals) suggest reduced membrane protein - pointing toward hereditary spherocytosis or elliptocytosis. However, interpretation depends on the lab's reference range and whether this is expressed as raw MFI or as a ratio.
• If this is MCV in fl: 792 fL is impossible (normal MCV in a neonate is 95-115 fL). This may be a platelet MFI or a flow cytometry parameter.
• Clarification of what instrument/assay this comes from is needed.

Immediate Management Priorities

1. Continue phototherapy - bilirubin 17.6 at day 10 requires ongoing phototherapy (threshold for term neonate at day 10+ is approximately 17-18 mg/dL for standard phototherapy; check the Bhutani nomogram zone)
2. Continue antibiotics for E. coli UTI (typically 10-14 days; IV then oral if sensitive)
3. Conjugated vs unconjugated split - Has conjugated bilirubin been checked? If conjugated >20% of total, this opens cholestatic causes (biliary atresia, neonatal hepatitis, metabolic liver disease)
4. Reticulocyte count - is there a hemolytic process? Expected to be elevated if hemolytic
5. Direct Coombs (DAT) - rule out immune hemolytic disease (ABO/Rh incompatibility)
6. Hb electrophoresis / HPLC - for thalassaemia (especially if ethnic background relevant)
7. G6PD assay and pyruvate kinase - enzyme deficiencies
8. Thyroid function (TSH, free T4) - congenital hypothyroidism screening result? (part of newborn screening)
9. Repeat full blood count + reticulocytes - Hb 11.3 is concerning; watch for drop requiring transfusion
10. Consider exchange transfusion if bilirubin continues to rise or crosses exchange threshold on the Bhutani nomogram (typically >20-25 mg/dL in term infant depending on risk factors)
11. Blood culture - if not already done, and reassess for clinical sepsis

Red Flags in This Baby

• Jaundice from day 2 = pathological onset (physiologic starts day 2-3 but does not usually require phototherapy)
• Still requiring phototherapy at day 10 = abnormal
• Confirmed E. coli UTI = active infection driving bilirubin
• Hb 11.3 = anaemia (for a term newborn, Hb <14 g/dL warrants investigation; <10 = significant)
• Blood film with tear drops + macrocytes + anisopoikilocytosis = underlying haematological condition until proven otherwise
• Bilirubin 17.6 at day 10 in an unwell baby = risk of kernicterus if not controlled

Bottom Line

• Tietz Textbook of Laboratory Medicine, 7th Ed - Jaundice in the Neonate section (Box 51.2 - classification of unconjugated hyperbilirubinemia causes including sepsis and hemolysis)

Critical Update: Retic 7.4 → 3.8, DCT Negative

What a Falling Reticulocyte Count Means Here

The Diagnosis Has Shifted: Congenital Dyserythropoietic Anaemia (CDA)

• Autosomal recessive (CDAN1 gene, chromosome 15)
• Macrocytic anaemia - matches this baby
• Megaloblastic-type marrow changes with internuclear chromatin bridges (~5% binucleated erythroblasts)
• Presents early in life with anaemia and jaundice
• ~80% require blood transfusion in the first month of life
• Ineffective erythropoiesis → unconjugated hyperbilirubinaemia despite low-normal reticulocytes

The UTI: Coincidental or Contributory?

Next Steps - What to Do Now

1. Bone marrow aspirate - the gold standard. Will show:
   • Erythroid hyperplasia
   • Internuclear chromatin bridges (CDA-I)
   • Binucleated/multinucleated erythroblasts
   • "Swiss cheese" heterochromatin on electron microscopy (CDA-I)
2. Genetic testing - CDAN1 mutation (CDA-I), SEC23B mutation (CDA-II), KIF23 (CDA-III). Send blood for gene panel.
3. Serum ferritin and LDH - expect elevated LDH (marrow cell destruction) and rising ferritin (iron loading from ineffective erythropoiesis and transfusions).
4. Haptoglobin - expect low/absent (intravascular cell destruction).
5. Urine urobilinogen - elevated in ineffective erythropoiesis.
6. Acidified serum test (Ham's test) - positive in CDA-II (HEMPAS) with some normal sera; helps subtype.

• Watch Hb closely - if it drops below 7-8 g/dL, this baby will need a packed red cell transfusion. 80% of CDA-I babies need transfusion in month 1.
• Continue phototherapy - until bilirubin falls to safe range; the ineffective erythropoiesis will continue to drive bilirubin production.
• Do not stop antibiotics - complete the UTI course regardless.
• Refer to paediatric haematology - this baby needs a specialist centre.
• Iron supplementation is CONTRAINDICATED - these babies iron-overload due to increased intestinal iron absorption from ineffective erythropoiesis. Do not give iron even if ferritin looks low initially.
• Folic acid supplementation is usually recommended to support the hyperactive (though ineffective) marrow.

Summary

• Henry's Clinical Diagnosis and Management by Laboratory Methods - Congenital Dyserythropoietic Anemias, p.689
• Harrison's Principles of Internal Medicine, 22e - Ineffective Hematopoiesis section

Transfusion Thresholds in Neonatal CDA: Latest Evidence (2024-2025)

The Core Limitation: No CDA-Specific Neonatal RCT Exists

1. General neonatal anaemia RCTs (TOP, ETTNO trials - preterm focused)
2. The 2024 JAMA Network Open Clinical Practice Guideline (Deschmann et al.)
3. CDA case series/reports
4. Expert consensus from paediatric haematology centres

Best Available General Neonatal Thresholds (Apply with Modification)

2024 Clinical Practice Guideline - JAMA Network Open [PMID: 38874929]

Recommended restrictive strategy for neonates <30 weeks gestation:

Royal Children's Hospital (Melbourne) 2024 - Neonatal RBC Thresholds

CDA-Specific Considerations That RAISE the Threshold

1. Ongoing ineffective erythropoiesis = marrow cannot compensate

2. 80% of CDA-I neonates need transfusion in month 1

3. Jaundice burden worsens with increased ineffective erythropoiesis

4. The 2025 CDA-I neonatal case report (Roose et al., Neonatology 2025) [PMID: 40472828]

5. CDA-IV case (Deguise et al., Pediatric Blood & Cancer 2023) [PMID: 36798023]

Practical Transfusion Decision Framework for This Baby

Transfusion Specifics for CDA

• Volume: 10-15 mL/kg packed red cells
• Rate: 2-5 mL/kg/hr (avoid rapid transfusion given cardiovascular load)
• Blood product: Leucodepleted, CMV-negative (or CMV safe), irradiated if any concern for immunodeficiency, ABO/Rh matched
• Frequency: Expect repeat transfusions every 4-6 weeks until definitive therapy
• Iron chelation: Begin monitoring ferritin from first transfusion; chelation (desferrioxamine or deferasirox) needed once overload develops - typically after 10-20 units or when ferritin >1000 μg/L
• Do NOT give supplemental iron at any point

Long-Term Treatment Horizon (Beyond Neonatal Period)

• IFN-α (interferon alpha): The established disease-modifying therapy for CDA-I. A 2026 study (J Clin Med, [PMID: 41598837]) examined patient-reported outcomes on interferon therapy, confirming ongoing relevance. Reduces transfusion dependence in many patients.
• Bone marrow transplant: Curative but reserved for severe transfusion-dependent cases.
• Genetic counselling: Both parents should be tested; CDAN1/C15ORF41 mutations, autosomal recessive.

Summary for This Baby Right Now

Diagnostic Criteria for Congenital Dyserythropoietic Anaemia (CDA)

Universal Criteria (All CDA Types)

Type-Specific Diagnostic Criteria

CDA Type I

• Macrocytic anaemia
• Anisopoikilocytosis, tear drop cells (dacrocytes)
• Basophilic stippling

• Erythroid hyperplasia
• Megaloblastic-type changes
• Internuclear chromatin bridges between adjacent erythroblasts - pathognomonic feature
• Binucleated erythroblasts (~5% of erythroid precursors)

• Heterochromatin denser than normal
• Sharply delineated clumps with small translucent vacuoles
• "Swiss cheese" appearance of nuclear heterochromatin - highly specific
• Cytoplasm penetrating through widened pores of nuclear envelope

• Acidified serum (Ham's) test: negative (distinguishes from CDA-II)

• CDAN1 mutation (encodes codanin-1) - present in majority
• C15ORF41 mutation - in a subset (CDA-Ib variant)

CDA Type II (HEMPAS)

• Normocytic anaemia (key difference from CDA-I)
• Anisopoikilocytosis

• Erythroid hyperplasia
• Binuclearity and multinuclearity in 10-40% of erythroid precursors
• Pluripolar mitotic figures
• Karyorrhexis

• Excess endoplasmic reticulum parallel to cell membrane
• "Double membrane" appearance in late erythroblasts and erythrocytes - pathognomonic

• Acidified serum (Ham's) test: POSITIVE with some (not all) normal heterologous sera - key diagnostic feature
• Sucrose haemolysis test: negative (distinguishes from PNH)
• Red cells react strongly with anti-I and anti-i antibodies
• Abnormal RBC antigen not found on normal or PNH cells; ~1 in 3 normal individuals have a naturally occurring IgM antibody against it

• SEC23B (CDAN2) mutation

CDA Type III

• Macrocytic anaemia

• Gigantoblasts (giant multinucleated erythroblasts) - hallmark finding
• Multinuclearity in 10-40% of precursors, more pronounced than CDA-II

• Acidified serum test: negative
• Red cells agglutinate with anti-I and anti-i

CDA Type IV

• Severe haemolytic anaemia often presenting in utero or at birth
• May require intrauterine transfusion
• Dyserythropoietic morphology plus a haemolytic component
• Variable multinuclearity
• KLF1 pathogenic variant on NGS (e.g. p.E325K) [PMID: 36798023]

Diagnostic Workup - Step by Step

Step 1: SUSPECT
  ├── Anaemia + jaundice + inappropriately low reticulocytes
  ├── DCT negative
  └── Abnormal blood film (macrocytes, tear drops, anisopoikilocytosis)

Step 2: SUPPORT
  ├── Elevated LDH
  ├── Low haptoglobin
  ├── Elevated unconjugated bilirubin
  └── Elevated ferritin (even without transfusions = iron loading from ineffective erythropoiesis)

Step 3: CONFIRM MORPHOLOGY
  └── Bone marrow aspirate + trephine
      ├── Erythroid hyperplasia
      ├── Dyserythropoiesis (internuclear bridges → CDA-I; multinuclearity → CDA-II/III)
      └── Electron microscopy if available (swiss cheese → CDA-I; double membrane → CDA-II)

Step 4: SEROLOGICAL SUBTYPING
  └── Ham's acidified serum test
      ├── Positive = CDA-II (HEMPAS)
      └── Negative = CDA-I or CDA-III

Step 5: GENETIC CONFIRMATION (NOW THE STANDARD OF CARE)
  └── Next-generation sequencing (NGS) gene panel
      ├── CDAN1 / C15ORF41 → CDA-I
      ├── SEC23B → CDA-II
      ├── KIF23 → CDA-III
      └── KLF1 → CDA-IV

Key Differentials to Exclude

For This Baby - Minimum Diagnostic Set

1. Bone marrow aspirate - look for internuclear bridges (CDA-I) or multinuclearity (CDA-II)
2. NGS gene panel (CDAN1, C15ORF41, SEC23B, KIF23, KLF1) - send whole blood
3. LDH, haptoglobin, ferritin - confirm ineffective erythropoiesis pattern
4. Ham's acidified serum test - helps subtype while awaiting genetics
5. Hb electrophoresis/HPLC - rule out thalassaemia
6. PK enzyme assay - rule out PK deficiency mimicking CDA-I

• Henry's Clinical Diagnosis and Management by Laboratory Methods - Congenital Dyserythropoietic Anemias, p.689
• Quick Compendium of Clinical Pathology, 5th ed - Section 4.2.5 CDA
• Moreno-Carralero et al. (2018). Clinical and genetic features of CDA. Eur J Haematol. [PMID: 29901818]