A 3-year-old girl presents with history of recurrent pyogenic infections (otitis media, pneumonia, skin abscesses) since infancy. Parents note that her hair is silvery-gray and her skin is lighter than other family members. She has nystagmus and photophobia. On examination: partial oculocutaneous albinism (hypopigmented skin, light-colored iris with transillumination), silvery hair, and hepatosplenomegaly. Peripheral smear report shows large azurophilic cytoplasmic granules in neutrophils.
🎯 Task (examiner observed): Recognize this as Chédiak-Higashi syndrome (CHS). Discuss the pathognomonic finding (giant granules in leukocytes), the underlying genetic defect (LYST gene), clinical features (partial albinism, recurrent infections, bleeding tendency, neurologic deterioration, accelerated phase), diagnostic workup, and management (prophylactic antibiotics, HSCT, accelerated phase treatment).
⚡ PATHOGNOMONIC FINDING: Giant cytoplasmic granules in neutrophils, eosinophils, basophils, monocytes, and lymphocytes on peripheral smear.
⚠️ CLINICAL RED FLAGS FOR CHÉDIAK-HIGASHI (Nelson's Chapter 170):
• Partial oculocutaneous albinism (silvery-gray hair, hypopigmented skin, iris transillumination)
• Recurrent pyogenic infections (S. aureus, Streptococcus, gram-negative bacteria)
• Neurologic manifestations (nystagmus, peripheral neuropathy, ataxia, seizures)
• Bleeding diathesis (easy bruising, epistaxis – due to platelet storage pool defect)
• Accelerated phase (hemophagocytic lymphohistiocytosis-like syndrome: fever, hepatosplenomegaly, lymphadenopathy, pancytopenia)
💡 Examiner instruction: Candidate must: (1) identify Chédiak-Higashi syndrome from the triad of albinism, recurrent infections, and giant granules, (2) describe the LYST gene defect and pathophysiology (defective phagosome-lysosome fusion), (3) order diagnostic tests (peripheral smear, platelet aggregation, NK cell function, genetic testing), (4) discuss accelerated phase recognition and treatment, (5) outline definitive management with HSCT, and (6) provide genetic counseling (autosomal recessive).
🔬 Diagnostic Workup for Chédiak-Higashi Syndrome
1Peripheral Blood Smear Demonstrates giant azurophilic granules in neutrophils, eosinophils, basophils, monocytes, and lymphocytes. Pathognomonic and readily available.
2Hair Shaft Microscopy Shows irregular clumping of melanin in hair shafts (large pigment granules). Differentiates from other forms of albinism.
3Neutrophil Function Assays • Chemotaxis: Impaired. • Bactericidal activity: Delayed due to defective phagosome-lysosome fusion. • Oxidative burst (DHR): Normal (differentiates from CGD).
5NK Cell Function Markedly decreased natural killer cell activity – contributes to susceptibility to EBV and accelerated phase.
6Genetic Testing (LYST gene) Sequence analysis of LYST (lysosomal trafficking regulator) gene on chromosome 1q42.3 confirms diagnosis. Identifies mutations for carrier detection and prenatal diagnosis.
📋 DIAGNOSTIC CRITERIA (Nelson's):
• Clinical: Partial oculocutaneous albinism + recurrent pyogenic infections + neurologic abnormalities.
• Laboratory: Giant granules in leukocytes (pathognomonic).
• Confirmatory: LYST gene mutation or abnormal NK cell function / chemotaxis.
• Accelerated phase: Fever, hepatosplenomegaly, lymphadenopathy, pancytopenia, hyperferritinemia, hemophagocytosis on bone marrow.
🧬 GENETICS (Nelson's Chapter 170):
Chédiak-Higashi syndrome is caused by mutations in the LYST gene (lysosomal trafficking regulator) on chromosome 1q42.3. Autosomal recessive inheritance. Protein defect disrupts intracellular protein trafficking, leading to enlarged lysosomes in various cell types (melanocytes, leukocytes, platelets, neurons).
❓ Q1 (Examiner): “What is the most likely diagnosis in this child with partial albinism, silvery hair, recurrent infections, nystagmus, and giant neutrophil granules?”
✅ Chédiak-Higashi syndrome (CHS). The combination of partial oculocutaneous albinism (silvery hair, nystagmus, photophobia), recurrent pyogenic infections, and the pathognomonic finding of giant azurophilic granules in neutrophils is diagnostic of CHS.
❓ Q2 (Examiner): “What is the genetic defect and inheritance pattern in Chédiak-Higashi syndrome?”
✅ Mutations in the LYST gene (lysosomal trafficking regulator) on chromosome 1q42.3. Autosomal recessive inheritance. The defective protein disrupts intracellular vesicle trafficking, leading to abnormally enlarged lysosomes and granules in various cell types.
❓ Q3 (Examiner): “Why does this child have recurrent pyogenic infections despite normal neutrophil count?”
✅ Neutrophils in CHS have impaired chemotaxis (delayed migration) and defective phagosome-lysosome fusion. Although they can engulf bacteria, they cannot efficiently kill them due to delayed delivery of lysosomal enzymes. This results in recurrent bacterial infections, especially with Staphylococcus aureus, Streptococcus, and gram-negative rods.
❓ Q4 (Examiner): “What is the pathognomonic laboratory finding in CHS?”
✅ Giant azurophilic granules in peripheral blood leukocytes (neutrophils, eosinophils, basophils, monocytes, and lymphocytes). These are enlarged lysosomal granules visible on routine Wright-stained smear. This finding is diagnostic and should prompt immediate suspicion.
❓ Q5 (Examiner): “What is the ‘accelerated phase’ of Chédiak-Higashi syndrome? How do you recognize and treat it?”
✅ The accelerated phase is a hemophagocytic lymphohistiocytosis (HLH)-like syndrome triggered often by EBV infection. Features: unexplained fever, massive hepatosplenomegaly, lymphadenopathy, pancytopenia, hyperferritinemia, hypertriglyceridemia, hemophagocytosis in bone marrow. Treatment: HLH-94/HLH-2004 protocol (etoposide, dexamethasone, cyclosporine) followed by hematopoietic stem cell transplantation (HSCT). Without treatment, accelerated phase is fatal.
❓ Q6 (Examiner): “What is the definitive treatment for Chédiak-Higashi syndrome?”
✅ Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment. It corrects the hematologic and immunologic defects (prevents recurrent infections and accelerated phase). However, it does NOT correct the neurologic deterioration or oculocutaneous albinism. HSCT is ideally performed before the onset of accelerated phase or severe neurologic involvement.
❓ Q7 (Examiner): “What supportive and prophylactic measures are used in CHS patients before transplant?”
✅ • Prophylactic antibiotics: TMP-SMX (prevents PJP and bacterial infections). • Ascorbic acid (vitamin C): High-dose vitamin C (200-500 mg/day) may improve neutrophil function and chemotaxis in some patients (limited benefit). • Avoid live viral vaccines (risk of vaccine-associated disease). • Prompt antibiotics for any febrile illness. • Avoid NSAIDs/aspirin due to bleeding tendency (platelet storage pool defect). • Sun protection (wide-brimmed hats, sunscreen for albinism). • Regular eye exams for nystagmus, strabismus, and visual impairment.
❓ Q8 (Examiner): “What is the cause of bleeding tendency in CHS?”
✅ Platelet dense granule deficiency (storage pool defect). Platelets lack dense granules (which store ADP, serotonin, calcium), leading to impaired platelet aggregation. Clinically: easy bruising, epistaxis, prolonged bleeding time. Normal platelet count. Desmopressin (DDAVP) may help for minor bleeding; platelet transfusion for severe bleeding.
❓ Q9 (Examiner): “What is the characteristic hair finding in CHS and how is it different from other forms of albinism?”
✅ Hair shaft microscopy in CHS shows irregular clumps of melanin (large, uneven pigment aggregates) giving a silvery-gray appearance. In other oculocutaneous albinisms, melanin distribution is more uniform. The giant melanosomes in hair are analogous to the giant granules in leukocytes.
❓ Q10 (Examiner): “What neurologic manifestations occur in CHS?”
✅ Progressive neurologic deterioration begins in late childhood or adolescence: peripheral neuropathy, ataxia, tremor, parkinsonism, cognitive decline, seizures, and cranial nerve palsies. These are due to abnormal lysosomal accumulation in neurons and are NOT corrected by HSCT. Early HSCT may slow progression but does not reverse existing damage.
❓ Q11 (Examiner): “How do you differentiate CHS from other syndromic albinisms (Hermansky-Pudlak, Griscelli)?”
✅ • CHS: Giant leukocyte granules, neutropenia/chemotaxis defect, recurrent infections, nystagmus, accelerated phase. • Hermansky-Pudlak (HPS): Oculocutaneous albinism + bleeding diathesis (platelet dense granule deficiency) + pulmonary fibrosis + granulomatous colitis. NO giant granules, no infection predisposition. • Griscelli syndrome: Silvery hair + partial albinism + variable immunodeficiency. Types: Type 1 (neurologic), Type 2 (hemophagocytic syndrome, similar to CHS accelerated phase), Type 3 (isolated albinism). No giant leukocyte granules. Genetic testing distinguishes.
❓ Q12 (Examiner): “What is the role of ascorbic acid (vitamin C) in CHS?”
✅ High-dose ascorbic acid (200-500 mg/day) has been reported to improve neutrophil chemotaxis and bactericidal activity in some CHS patients by reducing oxidative damage and stabilizing microtubules. However, clinical benefit is inconsistent and it does not prevent accelerated phase or neurologic deterioration. It is an adjunct, not a substitute for HSCT.
📢 Examiner probe: “What infections are most common in CHS?” → Staphylococcus aureus, Streptococcus pyogenes, gram-negative enteric bacteria (E. coli, Klebsiella), and Candida. Fungal infections are less common than in CGD.
👪 Genetic Counseling & Parental Communication (Candidate Role-Play)
🗣️ Candidate Task (Examiner role-playing as parent):
Examiner says: “Doctor, we just found out our 3-year-old daughter has Chédiak-Higashi syndrome. What does this mean? Can she be cured? Will she have more infections? What about her eyes and hair? And what about our next baby?”
🎯 Your response should address:
✅ MODEL CANDIDATE REPLY (TOACS):
“I understand this is overwhelming news. Let me explain what we know about Chédiak-Higashi syndrome.”
1. What is CHS?
“It’s a rare genetic condition where certain cells in the body – especially infection-fighting white blood cells, platelets, pigment cells, and nerve cells – don’t work properly because tiny structures inside them are abnormally large. This leads to three main problems: (a) recurrent infections (because white blood cells can’t kill bacteria effectively), (b) easy bruising/bleeding (due to platelets not working well), and (c) partial albinism (silvery hair, light skin, nystagmus, light sensitivity).”
2. Can she be cured?
“The only potential cure is a bone marrow transplant (hematopoietic stem cell transplantation). This can fix the blood and immune system problems – so it prevents severe infections and the dangerous ‘accelerated phase.’ However, it will not reverse the light coloring of her skin/hair or any existing nerve damage. The transplant is safest when done early, before severe complications.”
3. What about infections?
“Until transplant, we will give daily antibiotic medicine (trimethoprim-sulfamethoxazole) to help prevent bacterial infections. Any fever needs prompt medical attention. She should avoid live vaccines (MMR, varicella) because her immune system cannot handle them safely.”
4. What about her eyes and hair?
“The silvery hair and light skin are permanent – they don’t cause medical harm but will need sun protection (sunscreen, hats). The nystagmus (eye shaking) and light sensitivity (photophobia) may improve slightly with tinted glasses or contact lenses. An eye specialist will monitor her vision regularly.”
5. Future pregnancies (recurrence risk):
“This is an autosomal recessive condition. That means you and your partner are each carriers. For each future pregnancy, there is a 25% chance of another affected child, 50% chance of a carrier, and 25% chance unaffected. We can offer prenatal testing (chorionic villus sampling or amniocentesis) and preimplantation genetic diagnosis for future pregnancies if you wish. Genetic counseling will help you understand these options.”
6. Support:
“We will refer you to a pediatric immunologist and transplant center. The immunology team will coordinate care, prophylactic antibiotics, and help you decide about transplant timing. You are not alone – there are support groups and resources we can share.”
💡 Examiner assessment of counseling: Empathy, clarity, appropriate medical facts, addressing concerns (cure, infections, recurrence risk), and offering next steps (referral, genetic counseling).
🧬 Genetics LYST gene (1q42.3) mutations → defective lysosomal trafficking → giant cytoplasmic granules in all granule-containing cells.
🔬 Pathognomonic finding Giant azurophilic granules in neutrophils, eosinophils, monocytes, and lymphocytes on peripheral smear.
🦠 Immunologic defect Impaired chemotaxis, defective phagosome-lysosome fusion, decreased NK cell activity → recurrent S. aureus, Strep, gram-negative infections.
🩸 Bleeding defect Platelet dense granule deficiency (storage pool defect) → prolonged bleeding time, easy bruising.
⚡ Accelerated phase (HLH-like) Triggered by EBV or other viruses → fever, hepatosplenomegaly, pancytopenia, hemophagocytosis. Requires HLH-directed therapy (etoposide, steroids) then HSCT.
💉 Definitive treatment Allogeneic HSCT corrects hematologic/immunologic defects but does NOT reverse neurologic disease or albinism. Early transplantation before accelerated phase improves outcomes.
👪 Genetic counseling Autosomal recessive → 25% recurrence risk. Prenatal diagnosis available by molecular testing or electron microscopy of fetal blood for giant granules.
📖 Nelson's Textbook Reference (Chapter 170 – Disorders of Phagocyte Function):
“Chédiak-Higashi syndrome is a rare autosomal recessive disorder caused by mutations in LYST. Patients present with partial oculocutaneous albinism, recurrent pyogenic infections, and a bleeding diathesis. The diagnosis is established by the finding of giant granules in neutrophils. The accelerated phase, resembling hemophagocytic lymphohistiocytosis, is a medical emergency. Hematopoietic stem cell transplantation is the only curative therapy for the immunologic and hematologic manifestations but does not prevent neurologic deterioration.”
⭐ TOACS TAKE-HOME POINTS:
1. Giant granules in neutrophils + partial albinism + recurrent infections = CHS until proven otherwise.
2. Pathognomonic: peripheral smear with giant azurophilic granules.
3. Defect: LYST gene → defective phagosome-lysosome fusion.
4. Accelerated phase = HLH-like syndrome (fever, pancytopenia, hepatosplenomegaly) – treat with HLH protocol, then HSCT.
5. Definitive treatment: HSCT (corrects immunity, not neurology).
6. Supportive care: prophylactic TMP-SMX, vitamin C (limited benefit), sun protection.
7. Autosomal recessive → 25% recurrence risk → offer prenatal diagnosis.
8. Differentiate from Hermansky-Pudlak (no infections, pulmonary fibrosis) and Griscelli (no giant granules).
🔗 Additional resources:
• Paeds.online – Pakistan's Pediatric Study Platform
• National Organization for Rare Disorders (NORD) – Chédiak-Higashi Syndrome
• Histiocyte Society – HLH treatment protocols