• LAD is very rare: estimated incidence of approximately 1 per 1,000,000 live births worldwide.
• LAD-I (the classic and most common subtype) accounts for the vast majority of cases.
• No specific ethnic predilection, though consanguinity substantially increases risk given autosomal recessive inheritance.

• Neonates/early infancy: The hallmark presentation is in the neonatal period — delayed umbilical cord separation and omphalitis are often the first clues ^[1].
• Severe (complete deficiency) phenotypes present within weeks of birth; moderate (partial deficiency) phenotypes may present later in infancy or early childhood.

• Consanguinity (autosomal recessive inheritance — parents who are carriers)
• Family history of early infant death due to overwhelming infection
• In the Hong Kong context, while LAD is rare, awareness is important because:
  • Hong Kong has a robust newborn examination system; delayed cord separation should trigger referral.
  • Phagocyte defects account for approximately 14.9% of all primary immunodeficiencies ^[1].
  • BCG vaccination is given at birth in Hong Kong — phagocyte defects (including CGD and LAD) can present with disseminated BCG disease, making early recognition critical.

This is a beautifully orchestrated, multi-step process:

Step-by-step:

1. Margination: Neutrophils move from the centre of the blood vessel to the periphery (near the endothelium). This happens naturally in post-capillary venules where flow is slower.

2. Rolling: Mediated by selectins (E-selectin, P-selectin on endothelium; L-selectin on leukocytes) and their carbohydrate ligands, particularly sialyl-Lewis X (sLeX). These are weak, transient bonds → the neutrophil "rolls" along the endothelium like a ball rolling along a surface. This is the step affected in LAD-II.

3. Firm Adhesion (Arrest): The critical step. Chemokines released at the infection site activate the neutrophil, causing a conformational change in surface integrins — specifically the β2-integrin family (CD18/CD11 complexes):

   • LFA-1 (CD11a/CD18) — "Lymphocyte Function-associated Antigen-1"
   • Mac-1 (CD11b/CD18) — "Macrophage-1 antigen" (also called CR3, complement receptor 3)
   • p150,95 (CD11c/CD18)

   These integrins bind to ICAM-1 and ICAM-2 (Intercellular Adhesion Molecules) on the endothelial surface → firm adhesion. This is the step affected in LAD-I (the common form).

4. Transmigration (Diapedesis): The neutrophil squeezes between endothelial cells, crossing the basement membrane into the tissue. This requires PECAM-1 (CD31) and other molecules.

5. Chemotaxis: Once in the tissue, the neutrophil follows a chemical gradient (C5a, IL-8, LTB4, bacterial formyl peptides) to the site of infection, where it performs phagocytosis and killing.

The neutrophil is the first-line phagocyte of innate immunity, essential for defence against bacteria and fungi. In LAD:

1. Infection begins → endothelium becomes activated → upregulates ICAM-1, selectins
2. Chemokines are released → should activate neutrophil integrins
3. In LAD-I: Neutrophils lack CD18 → cannot firmly adhere → continue flowing past in the bloodstream → never reach the tissue
4. Bacteria proliferate unchecked in the tissue → spreading infection, tissue necrosis
5. The bone marrow compensates by producing more neutrophils → marked peripheral leukocytosis
6. But all these extra neutrophils are useless — they are trapped in the circulation

Pus = collection of dead neutrophils + tissue debris + bacteria. If neutrophils cannot leave the bloodstream, they never accumulate at the infection site → absent pus formation despite severe infection ^[1]. This is a cardinal feature.

Clinical features: poor wound healing with absent pus formation ^[1]

Normal umbilical cord separation (typically 7–14 days of life) is an inflammatory process:

• After the cord is clamped, the stump undergoes dry gangrene
• Neutrophils migrate into the cord stump → enzymatic digestion and separation
• In LAD: Neutrophils cannot migrate into the tissue → the normal inflammatory separation process is severely impaired → delayed separation (often > 30 days) with associated omphalitis (umbilical stump infection) ^[1]

Wound healing requires:

• Neutrophils (early phase: debridement, clearing bacteria)
• Monocytes/macrophages (later phase: tissue remodelling)

Both cell types require β2-integrins for tissue entry → in LAD-I, wound healing is impaired at every stage.

The oral cavity is heavily colonised with bacteria. Normal gingival health depends on constant neutrophil surveillance in the gingival crevice. Without neutrophil migration:

• Bacteria proliferate → severe, destructive periodontitis
• Premature tooth loss is common in moderate LAD-I patients who survive infancy

Because the defect is in neutrophil adhesion (innate immunity), the organisms are those normally controlled by neutrophils:

Phagocyte defects commonly cause recurrent bacterial infections. Common pathogens: skin commensals, fungi ^[1]

• Severe LAD-I (< 2% CD18): Without haematopoietic stem cell transplantation (HSCT), most children die within the first 1–2 years of life from overwhelming sepsis or necrotising infections.
• Moderate LAD-I (2–30% CD18): May survive to childhood or adulthood but with significant morbidity — severe periodontitis, recurrent infections, impaired quality of life.

LAD is classified under phagocyte defects in the IUIS classification of primary immunodeficiencies.

Warning signs for PID in children include: ≥ 4 new ear infections in 1 year, ≥ 2 serious sinus infections in 1 year, ≥ 2 months on antibiotics with little effect, ≥ 2 pneumonias in 1 year, failure to thrive, recurrent deep skin/organ abscesses, persistent thrush after age 1, need for IV antibiotics, ≥ 2 deep-seated infections, family history of PID.

In the approach to PID: the type of infection suggests the immune defect — bacterial infections (especially skin, soft tissue, lung) with absent pus and very high WCC point to phagocyte adhesion defects.

Phagocyte defects present with recurrent bacterial and fungal infections, particularly of skin, lungs, and lymph nodes.

Flow cytometry for CD18 (and CD11a, CD11b, CD11c) expression on leukocytes is the key diagnostic test for LAD-I.

Neutrophil function tests include: NBT (nitroblue tetrazolium) test or DHR (dihydrorhodamine) flow cytometry for oxidative burst (CGD), and flow cytometry for adhesion molecules (LAD).

This is the most important differential to distinguish from LAD, and is a favourite exam question ^[4].

• Defect: Maturation arrest of neutrophil precursors in bone marrow (mutations in ELANE, HAX1, G6PC3, etc.)
• Presentation: Recurrent severe bacterial infections from early infancy (similar to LAD)
• Key difference from LAD:
  • Neutropenia (ANC < 200/μL) — the OPPOSITE of LAD which has marked neutrophilia
  • Pus may still be absent (no neutrophils to form pus), but the mechanism is different (not enough neutrophils produced vs. neutrophils can't leave vessels)
• Why it matters: Both LAD and severe congenital neutropenia present with infections + absent pus, but the CBC immediately distinguishes them — sky-high neutrophils in LAD vs. near-zero neutrophils in Kostmann

• Defect: ELANE gene mutation → periodic oscillations in neutrophil count with a cycle of approximately 21 days
• Presentation: Recurrent fevers, mouth ulcers, and infections occurring in a predictable cyclical pattern
• Key difference from LAD: Neutropenia is episodic (not constant); between episodes, the WCC normalises. Serial CBCs over 6–8 weeks demonstrate the cyclical pattern. LAD has persistent neutrophilia.

• Defect: Absence of specific (secondary) granules in neutrophils → impaired bactericidal function
• Very rare
• Key difference: Neutrophils are present and can migrate but lack granule contents. Diagnosed on neutrophil morphology (bilobed nuclei, absent granules on smear).

• Defect: LYST gene mutation → defective lysosomal trafficking → giant granules in leukocytes → impaired chemotaxis and killing
• Key features: Partial oculocutaneous albinism, recurrent pyogenic infections, giant granules visible on peripheral blood smear, progressive neurological deterioration, risk of haemophagocytic lymphohistiocytosis (HLH)
• Key difference from LAD: Albinism is the distinguishing clinical clue. Giant granules on blood film are pathognomonic.

• Defect: Combined T-cell and B-cell deficiency (many genetic causes; most common X-linked IL2RG)
• Presentation: All infections — bacterial, viral, fungal, opportunistic (PJP, BCG dissemination, Candida) ^[2]
• Key differences from LAD:
  • Low absolute lymphocyte count (ALC < 2500/mL in infants) ^[2] — LAD has normal lymphocytes
  • Failure to thrive, chronic diarrhoea, absent thymic shadow on CXR
  • Infections include viruses and opportunistic organisms (LAD is mainly bacterial/fungal)
  • WCC may be low or normal (not high)
  • No delayed cord separation

• Defect: STAT3 mutation (AD, loss of function) → impaired Th17 response ^[2]
• Clinical features: pneumatocele, mucocutaneous Candidiasis, retained primary teeth, minimal trauma fracture and scoliosis ^[1]
• Key shared feature with LAD: Recurrent skin abscesses (often S. aureus)
• Key differences from LAD:
  • Abscesses in HIES are classically "cold" (non-tender, non-inflamed) but DO contain pus — the neutrophils can reach the tissue, they just don't mount a proper inflammatory response
  • Very high IgE levels, high absolute eosinophil count ^[2]
  • Characteristic facies (coarse), skeletal abnormalities
  • Normal neutrophil count
  • CXR showing massive pneumatoceles ^[2]

• Defect: WAS gene mutation → defective WASp protein → impaired actin cytoskeleton in haematopoietic cells
• Clinical features: triad of immunodeficiency + thrombocytopenia + eczema ^[1]
• Micro-thrombocytopenia (low AND small platelets), bloody diarrhoea ^[2]
• Key difference from LAD: The triad is distinctive — eczema + small platelets + immunodeficiency. Bleeding tendency. LAD has no thrombocytopenia or eczema.

The following constellation should trigger investigation for LAD:

1. Recurrent severe bacterial/fungal infections beginning in the neonatal period or early infancy
2. Delayed umbilical cord separation (> 3–4 weeks, often > 30 days) with omphalitis ^[1]
3. Absent pus formation at sites of infection despite severe tissue infection ^[1]
4. Poor wound healing — wounds dehisce, ulcers fail to close ^[1]
5. Marked persistent leukocytosis/neutrophilia even between infectious episodes ^[1]
6. Severe periodontitis/gingivitis with premature tooth loss (in moderate phenotype surviving to childhood)

Approach to diagnosis of PID: Clinical history → Physical examination → Phenotypic investigations (Ig levels, vaccine responses, T/B/NK cell enumerations, lymphocyte subsets, cell function) → Genetic testing ^[5]

Definitive diagnosis of LAD-I requires:

For LAD-II and LAD-III, additional specific tests are needed (see below).

HSCT replaces the patient's defective haematopoietic system (including all leukocytes) with donor-derived stem cells that carry a functional ITGB2 gene. The donor's neutrophils, monocytes, and lymphocytes will express normal CD18 → normal β2-integrin expression → restored adhesion and tissue migration.

This is the only curative treatment for severe LAD-I and LAD-III.

HSCT is the treatment for severe combined immunodeficiency, CGD, and other severe PIDs ^[2]

This hierarchy is the same as for all paediatric HSCT indications. The reason for the order is that better HLA matching → lower risk of graft-versus-host disease (GVHD) and graft failure:

Before HSCT, a conditioning regimen is given to:

1. Create "space" in the bone marrow for donor cells to engraft
2. Suppress the host immune system to prevent rejection of the graft

For LAD, either myeloablative conditioning (MAC) or reduced-intensity conditioning (RIC) can be used:

Paediatric dosing considerations: All conditioning agents are dosed based on body weight (mg/kg) or body surface area (mg/m²) in children. Busulfan requires therapeutic drug monitoring (TDM) in children because pharmacokinetics are highly variable with age — neonates and infants metabolise busulfan differently from older children.

After transplant, careful monitoring is essential:

1. Engraftment: Check CBC daily → rising neutrophil count (ANC > 500 for 3 consecutive days) indicates engraftment, usually by day +14 to +28. In LAD specifically, confirm CD18 expression on donor-derived neutrophils by flow cytometry.
2. Chimerism: PCR-based chimerism studies to determine proportion of donor vs. host cells. Mixed chimerism is acceptable if CD18+ neutrophils are sufficient (even partial donor engraftment can correct the phenotype because even a moderate percentage of CD18-expressing neutrophils provides clinical benefit).
3. Graft-versus-Host Disease (GVHD): Monitor for skin rash, diarrhoea, liver dysfunction → acute GVHD; scleroderma-like skin changes, dry eyes/mouth, bronchiolitis obliterans → chronic GVHD.
4. Infection surveillance: Patient remains immunocompromised for months post-transplant during immune reconstitution. Prophylaxis against bacterial, viral (CMV, EBV), and fungal infections is essential.
5. Vaccination schedule: All previous vaccinations are "lost" after myeloablative HSCT → re-vaccination begins 6–12 months post-transplant per transplant centre protocol. Live vaccines (e.g. MMR, varicella) deferred until ≥ 24 months post-transplant and only if no active GVHD and no ongoing immunosuppression.

Why: Without functional neutrophil tissue migration, the child is defenceless against bacterial and fungal infections. Prophylactic antibiotics reduce the frequency and severity of breakthrough infections.

Treatment for Hyper-IgE syndrome: Septrin + IVIG + secukinumab; for CGD: Septrin + Itraconazole + HSCT ^[2]

The principle is analogous — co-trimoxazole (Septrin) is the backbone of prophylaxis across phagocyte defects.

Contraindications to co-trimoxazole:

• Sulfonamide allergy (rare but important — causes Stevens-Johnson syndrome/TEN)
• Severe renal impairment (dose adjustment needed)
• G6PD deficiency (sulfonamides can trigger haemolysis — relevant in Hong Kong where G6PD deficiency is prevalent, approximately 4% of males)
• Neonates < 2 months (risk of kernicterus due to bilirubin displacement)

When a child with LAD develops an acute infection, treatment must be:

• Empiric and broad-spectrum (cover Gram-positives, Gram-negatives, and consider fungi)
• Intravenous initially (poor tissue penetration is already a problem → ensure high serum drug levels)
• Prolonged (infections heal slowly because even with antibiotics killing bacteria, the wound healing process is impaired without neutrophils)
• Culture-directed as soon as microbiology results return

Surgical debridement may be needed for necrotic wounds or spreading soft-tissue infections, but wound healing will be poor — plan for prolonged wound care.

Why: In life-threatening infections unresponsive to antibiotics, donor granulocyte transfusions can temporarily provide functional neutrophils that CAN migrate into tissue (because they have normal CD18).

Indications:

• Severe, refractory infection not responding to optimal antimicrobials
• Bridge to HSCT when transplant is imminent but infection is out of control

Limitations:

• Short-lived (transfused neutrophils survive only 6–24 hours)
• Risk of transfusion reactions (fever, rigors, TRALI)
• HLA alloimmunisation (can jeopardise future HSCT — use irradiated, CMV-negative products if possible)
• Logistically difficult — requires a willing donor, apheresis collection, and rapid administration

Paediatric consideration: Irradiation of granulocyte products is essential to prevent transfusion-associated GVHD in immunodeficient children.

Why this is generally NOT helpful in LAD: G-CSF stimulates the bone marrow to produce more neutrophils. In LAD, the problem is NOT neutrophil production (they already have too many neutrophils) — the problem is that neutrophils cannot adhere and migrate. Giving G-CSF would simply increase the already sky-high peripheral neutrophil count without clinical benefit.

Exception: In some moderate LAD-I cases, very high-dose G-CSF has been tried to increase the absolute number of neutrophils to the point where even the small percentage with residual CD18 expression can provide some tissue defence. This is anecdotal and not standard practice.

• Meticulous daily skin care: Regular bathing, moisturisation, prompt attention to any skin break
• Wound management: Aggressive cleaning, debridement of necrotic tissue, negative-pressure wound therapy if needed
• Avoid unnecessary skin breaks: Minimise venepuncture, avoid intramuscular injections where possible (use IV or subcutaneous routes)
• Dental hygiene: Regular dental review from the time of tooth eruption (6 months); chlorhexidine mouthwash in older children; aggressive periodontal care

• Chronic infections → catabolic state → failure to thrive
• Plot growth on standard WHO/Hong Kong growth charts at every visit
• Dietitian involvement if weight faltering
• Ensure adequate caloric, protein, and micronutrient intake
• Consider nasogastric or gastrostomy feeding if oral intake is insufficient

• Genetic counselling: AR inheritance → 25% recurrence risk. Discuss carrier testing for parents and siblings. Offer prenatal diagnosis for future pregnancies.
• Psychological support: Chronic illness in a child places enormous stress on the family. Social work referral, peer support groups (e.g. Primary Immunodeficiency Association of Hong Kong).
• Education: Teach parents to recognise early signs of infection (fever, redness, swelling — noting that pus will be absent), when to seek urgent medical care, and how to administer prophylactic medications.
• School integration: When the child is old enough, liaise with school about infection control precautions, avoiding contact with actively infectious classmates.

• Oral fucose supplementation: This is unique to LAD-II. The defect is in the GDP-fucose transporter → impaired fucosylation of selectin ligands. Oral fucose (given as dietary supplement) can bypass the defective transporter to some extent by providing excess substrate.
  • Dose: Typically 25–150 mg/kg/dose given 3–5 times daily (no standardised dosing — titrated to clinical and laboratory response)
  • Monitoring: Check CD15s (sLeX) expression on neutrophils by flow cytometry; assess neutrophil rolling function; clinical response (reduction in infection frequency)
  • Response is variable: Some patients show improved selectin-mediated rolling and reduced infections; others show minimal response
  • Does NOT correct the intellectual disability, short stature, or Bombay blood group (these reflect fucosylation defects in other tissues/systems)
• HSCT is generally NOT performed for LAD-II because the disease is milder than severe LAD-I and the neurological features are not corrected by transplant.

• HSCT: Curative for both the immunodeficiency AND the bleeding tendency (corrects defective integrin activation in both leukocytes and platelets by replacing the haematopoietic system)
• Platelet transfusions: For acute bleeding episodes (pending HSCT)
• Avoid antiplatelet agents: Aspirin and NSAIDs are contraindicated as they further impair already-defective platelet function

• Rationale: Since LAD-I is caused by a single-gene defect (ITGB2), it is an ideal candidate for gene therapy — introduce a functional copy of ITGB2 into the patient's own haematopoietic stem cells, then reinfuse them.
• Approach: Ex vivo gene therapy using lentiviral vectors to transduce autologous CD34+ haematopoietic stem cells with a functional ITGB2 cDNA.
• Current status (2025–2026): Phase I/II clinical trials are ongoing. Early results show feasibility and partial correction of CD18 expression, but long-term safety and durability of engraftment are still being evaluated.
• Advantages over HSCT: No need for a donor; no risk of GVHD; reduced conditioning intensity may be possible.
• Limitations: Insertional mutagenesis risk (though lower with lentiviral vectors than earlier retroviral vectors); may not achieve 100% correction; very expensive; limited availability.

• No established role in LAD management currently
• Research is ongoing into whether modulating the immune response can provide any benefit, but this is not standard practice

Why: Without neutrophil tissue surveillance, local infections rapidly become systemic. Bacteria enter the bloodstream from any infected focus (skin, umbilical stump, lungs, gut). The child lacks the ability to contain infection locally because abscess formation (which walls off bacteria) requires neutrophil accumulation — something that cannot happen in LAD.

• Common organisms: Staphylococcus aureus, Pseudomonas aeruginosa, enteric Gram-negatives (E. coli, Klebsiella) ^[9]
• Clinical features: High fever, tachycardia, tachypnoea, hypotension → septic shock. Paradoxically, localising signs may be absent or minimal (no abscess, no fluctuance, no pus) even though the child is critically unwell.
• In neonates (age group: neonatal): Sepsis may present with non-specific signs — temperature instability (hypothermia or fever), poor feeding, lethargy, apnoea, jaundice. The very high WCC in LAD can be misinterpreted as "reactive leukocytosis from sepsis" rather than the underlying diagnosis.
• Mortality: Overwhelming sepsis is the leading cause of death in severe LAD-I (CD18 < 2%) — without HSCT, up to 60–80% die by age 2 years ^[1].

Why: Without neutrophils to contain and kill bacteria in skin and subcutaneous tissue, infections spread along fascial planes → necrotising fasciitis, cellulitis, and spreading gangrene. Unlike in immunocompetent children where necrotising fasciitis is typically caused by Group A Streptococcus and presents with erythema, blistering, and crepitus, in LAD the infection may spread insidiously because the normal inflammatory response (redness, swelling, warmth, pus) is blunted.

• Sites: Any site of skin breach — including minor wounds, insect bites, venepuncture sites, and surgical sites
• Clinical significance: May require extensive surgical debridement, but wound healing post-operatively is also impaired → creates a vicious cycle of surgery → poor healing → re-infection → more surgery

Why: The umbilical stump in the first days/weeks of life is colonised by bacteria. Normally, neutrophils migrate into the cord stump to control this. In LAD, bacteria invade the devitalised tissue unchecked → omphalitis ^[1]. If untreated, infection can spread to:

• Peritoneum → peritonitis
• Portal vein → portal vein thrombosis / pylephlebitis
• Bloodstream → neonatal sepsis

Usually present with omphalitis with delayed umbilical cord separation ^[1]

Why: The respiratory epithelium is constantly exposed to inhaled pathogens. Alveolar macrophages provide some defence, but neutrophils are the dominant effector cells for clearing bacterial pneumonia. Without neutrophil tissue entry, bacterial pneumonia becomes recurrent and difficult to treat.

• Recurrent episodes can lead to chronic lung damage (see structural complications below)
• Organisms: S. aureus, Pseudomonas aeruginosa, Klebsiella, Aspergillus spp. ^[9]

Why: The perianal region is heavily colonised with enteric bacteria. Minor mucosal breaks from stooling → bacterial entry → perianal abscess, perirectal abscess, or cellulitis. Because neutrophils cannot contain these, they spread and become chronic.

• Perianal fissures and fistulae may develop
• Chronic perianal sepsis significantly impairs quality of life

Why: BCG (Mycobacterium bovis BCG) is a live attenuated vaccine given at birth in Hong Kong. In children with phagocyte defects, BCG can disseminate because phagocytes cannot effectively control even attenuated mycobacteria.

• Although disseminated BCG is more classically associated with CGD and SCID ^[2], it can also occur in LAD, particularly if the infant has very severe disease
• Presents with regional lymphadenitis (axillary, if BCG was given in the left arm), progressive lymphadenopathy, hepatosplenomegaly, and eventually systemic dissemination with fever, weight loss, and multi-organ involvement
• Prevention: If LAD is suspected antenatally or at birth (e.g. family history), withhold BCG until diagnosis is clarified

Why: Neutrophils are the primary defence against filamentous fungi (e.g. Aspergillus) and are important for mucosal defence against Candida. Without neutrophil tissue surveillance:

• Invasive aspergillosis: Pulmonary, disseminated
• Invasive candidiasis: Oral, oesophageal, systemic
• These are life-threatening and require prolonged IV antifungal therapy

Why: Every phase of wound healing is compromised in LAD:

• Inflammatory phase (days 1–4): Requires neutrophil infiltration for debridement and bacterial clearance → absent in LAD
• Proliferative phase (days 4–21): Monocyte/macrophage infiltration drives granulation tissue formation and angiogenesis → also impaired (monocytes also require β2-integrins)
• Remodelling phase (weeks to months): Depends on prior phases being completed

Result: Wounds remain open, become secondarily infected, enlarge → chronic non-healing ulcers. Surgical wounds dehisce. Even minor procedures (e.g. circumcision, ear piercing, venepuncture) can become complicated.

Poor wound healing with absent pus formation ^[1]

Why: The gingival crevice (the groove between the tooth and gum) is constantly colonised by bacteria. Normal gingival health depends on a continuous stream of neutrophils migrating into the crevicular fluid — this is one of the highest rates of neutrophil emigration in the body. In LAD:

• No neutrophil gingival surveillance → bacteria proliferate in periodontal pockets
• Progressive destruction of the periodontium (gingiva, periodontal ligament, alveolar bone)
• Primary teeth: May become loose and fall out prematurely (typically by age 3–5 years in moderate LAD-I)
• Permanent teeth: Severe periodontitis → early loss of permanent dentition if untreated

Leukocyte adhesion deficiency → periodontitis ^[5]

This is particularly prominent in moderate LAD-I (CD18 2–30%) where children survive infancy but suffer from progressive, destructive periodontal disease throughout childhood and adolescence.

Why: Recurrent pneumonias → inadequate bacterial clearance → chronic infection → bronchial wall destruction → irreversible bronchial dilation (bronchiectasis)

• Mechanism: Each episode of pneumonia causes some parenchymal damage. Because healing is impaired AND infections are incompletely resolved, a cycle of infection → damage → more infection develops.
• Clinical features: Chronic productive cough, recurrent chest infections, progressive decline in lung function
• Monitoring: Regular chest imaging (HRCT) and pulmonary function tests in older children
• Relevance: Even after HSCT, structural lung damage (bronchiectasis) is irreversible — this underscores the importance of early transplantation before lung damage accumulates

• Chronic skin infections → extensive scarring, contractures
• Facial and limb scarring from recurrent soft tissue infections
• Impacts body image and psychosocial wellbeing, particularly in older children and adolescents

HSCT, while curative, carries significant risks — particularly in children who may already be debilitated by recurrent infections.

Why: Chronic infection → elevated metabolic demands + poor oral intake (painful gingivitis, systemic illness) + nutrient malabsorption (if GI infections) → caloric deficit → growth failure.

• Assessment: Plot weight, length/height, and head circumference on age-appropriate growth charts (WHO for 0–2 years; CDC or local HK charts for > 2 years) at every visit
• Intervention: Dietitian involvement, caloric supplementation, NG/gastrostomy feeding if needed

Why: In LAD-II, the defective GDP-fucose transporter affects fucosylation of glycoproteins throughout the body, not just on leukocytes. In the brain, fucosylated glycoproteins are essential for neuronal migration, synapse formation, and myelination during development → intellectual disability and psychomotor delay.

• This is a feature of LAD-II specifically — mental retardation, short stature ^[5]
• NOT a feature of LAD-I or LAD-III (the brain develops normally because CD18 / Kindlin-3 are not required for brain development)

• Chronic illness burden: Frequent hospitalisations, painful procedures, medication burden → anxiety, depression, behavioural issues in the child
• School absenteeism: Recurrent infections → missed school → academic difficulties
• Family impact: Parental stress, financial burden (especially if one parent needs to become a full-time caregiver), impact on siblings
• Body image: Scarring, disfigurement, short stature → low self-esteem in older children/adolescents
• Grief and bereavement: In severe LAD-I, some children die despite treatment — the family may need bereavement support; siblings may also be carriers