Genetic Testing for Hypertriglyceridemia

Background: Why Genetics Matter

• TG 150-899 mg/dL: usually polygenic - many common and rare variants with small individual effects
• TG >900 mg/dL: strongly suggests a large-effect monogenic disorder
• TG >1000 mg/dL: risk of pancreatitis rises sharply; lifetime risk ~5-20% depending on severity

Genetic Disorders Causing Hypertriglyceridemia

1. Familial Chylomicronemia Syndrome (FCS) - Monogenic, Autosomal Recessive

2. Multifactorial Chylomicronemia Syndrome (MCS) - Complex/Polygenic

• Heterozygous loss-of-function mutations in TG-raising genes (LPL, APOA5, etc.)
• Common pathogenic variants at multiple loci
• Secondary factors: obesity, diabetes, alcohol, medications

3. Familial Hypertriglyceridemia (Type IV) - Autosomal Dominant

• Population prevalence 5-10%
• Isolated VLDL elevation, TG usually 200-500 mg/dL
• Pathophysiology: overproduction of triglyceride-rich VLDL with normal apoB
• Specific causative gene(s) remain incompletely defined; often exacerbated by obesity and insulin resistance

4. Familial Combined Hyperlipidemia (Type IIB)

• Most common primary hyperlipoproteinemia (~1 in 100)
• Elevated LDL + TG (mixed pattern)
• Phenotypic heterogeneity within families
• No single definitive biochemical or genetic marker; diagnosis requires family history showing multiple lipid phenotypes

5. Dysbetalipoproteinemia (Type III) - APOE-related

• APOE e2/e2 genotype is the classic predisposing variant
• TG and cholesterol both elevated; characteristic broad-beta band on electrophoresis
• VLDL-C:TG ratio >0.3 (vs <0.2 in normal) is diagnostic
• APOE genotyping is the confirmatory genetic test

6. ApoC-III Excess

• Multiple polymorphisms in APOC3 gene (e.g., -455T/C, -482C/T, 1100C/T)
• ApoC-III inhibits LPL activity and promotes VLDL production
• Contributes to elevated TG, especially in metabolic syndrome and T2DM

When to Order Genetic Testing

Practical Testing Approach

• Lipoprotein electrophoresis (agarose gel): identifies Fredrickson type (I, IIB, III, IV, V)
• Panel C below shows chylomicronemia at origin (TG = 3840 mg/dL); Panel B shows type III beta-VLDL pattern

• FCS gene panel: sequences LPL, APOC2, APOA5, GPIHBP1, LMF1 for pathogenic variants
• APOE genotyping: for suspected type III
• ABCG5/ABCG8: for suspected beta-sitosterolemia
• ApoB measurement and TG:total cholesterol ratio help triage

Why It Matters Clinically (2026 Update)

Summary Table

CMV Retinitis

Overview

Epidemiology & Risk Factors

• CD4 count <50 cells/μL: highest risk (screening every 3 months)
• CD4 50-100 cells/μL: screen every 6 months
• CD4 >100 cells/μL: yearly screening
• HIV microangiopathy (cotton-wool spots) is a marker for increased CMV retinitis risk
• Also occurs in: bone marrow and solid organ transplant recipients, patients on chronic immunosuppressive therapy, congenital CMV
• Risk is higher in patients on systemic corticosteroids even after ART

Symptoms

• Often asymptomatic early (especially peripheral lesions)
• Floaters
• Scotomata (focal visual field defects)
• Peripheral visual field loss
• Reduced central acuity when macula is involved
• Photopsia

Fundoscopic Appearance

• Dense white/yellow areas of retinal infiltration and necrosis
• Prominent flame-shaped intraretinal hemorrhages
• Classic "pizza pie" or "Margherita pizza" appearance - white necrosis with bright red hemorrhage interspersed

• Granular white infiltrates with fewer hemorrhages
• Less vasculitis
• Can spread silently toward the macula over weeks

• Retinal vasculitis (vascular sheathing)
• Frosted branch angiitis - marked vascular sheathing in ~6%
• Optic neuritis from direct spread
• Mild anterior uveitis
• Minimal vitreous inflammation (unlike acute retinal necrosis)

Complications

Diagnosis

• Clinical: ophthalmoscopy showing characteristic fundus appearance is the primary diagnostic method
• CMV PCR (blood/vitreous): viremia usually present with active end-organ disease; supports diagnosis but can be present without retinitis
• CD4 count
• No biopsy needed in typical cases
• Differential: toxoplasma retinochoroiditis, progressive outer retinal necrosis (PORN/VZV), acute retinal necrosis, syphilis, HIV retinopathy, intraocular lymphoma

Treatment

First-Line: Valganciclovir (preferred - oral bioavailability = IV ganciclovir)

IV Ganciclovir (when PO not feasible)

• Main toxicity: myelosuppression/neutropenia - treat with G-CSF (filgrastim)

Alternative Systemic Agents (sight-threatening lesions, ganciclovir resistance, intolerance)

Local/Intravitreal Therapy (adjunct for sight-threatening lesions near optic nerve or macula)

• Intravitreal ganciclovir 2 mg/injection
• Intravitreal foscarnet 1.2 mg
• Intravitreal cidofovir 20 μg
• Note: ganciclovir implant marketing authorization has been withdrawn

ART (Cornerstone)

• ART is the mainstay of long-term management - restores immune function and CMV control
• Start ART promptly (as early as tolerated)

Drug Resistance

• UL97 kinase mutations: confer resistance to ganciclovir/valganciclovir; usually remain sensitive to foscarnet and cidofovir
• UL54 DNA polymerase mutations (in addition to UL97): confer resistance to ganciclovir, foscarnet, AND cidofovir
• Letermovir: novel mechanism (CMV terminase complex inhibitor); active against ganciclovir-resistant strains; used for prophylaxis in transplant recipients

Immune Recovery Uveitis (IRU)

• Cause: Rejuvenated immune response against residual CMV antigen after CD4 recovery
• Features: Marked vitritis, cystoid macular edema, epiretinal membrane, cataract - can progress to phthisis bulbi
• Treatment: Intravitreal or systemic corticosteroids (with caution)
• Paradoxically, patients with best immune recovery have highest IRU risk

Differential Diagnosis Summary

Monitoring

• Ophthalmology review every 2 weeks during active disease/induction
• Once stable on maintenance: monthly to 3-monthly
• Fundus photography and OCT useful for monitoring lesion borders and macular involvement

Causes of Blepharospasm

1. Primary (Essential / Idiopathic) Blepharospasm

• Etiology is idiopathic and likely multifactorial, possibly involving dysfunction of dopaminergic pathways within the basal ganglia
• Neuroimaging studies (PET-FDG, fMRI) show abnormal activity in: primary motor cortex, anterior cingulate gyrus, supplementary motor area, striatum, thalamus, inferior frontal lobes, pons, and cerebellum
• Pathologic changes have been identified in the primary motor cortex, anterior cingulate, and premotor/supplementary motor cortices
• No consistent neuropathologic lesion or neurochemical profile has been established
• Genetic basis is possible but few cases are clearly inherited; no association with known dystonia genes confirmed
• Predominantly women, onset in the sixth decade
• When combined with oromandibular dystonia (jaw, tongue spasms) = Meige syndrome (also called Brueghel syndrome)
• May also be associated with spasmodic dysphonia, torticollis, and other dystonic fragments

2. Secondary / Symptomatic Causes

A. Ocular Surface Disease (Reflex Blepharospasm)

• Dry eye syndrome
• Blepharitis (including rosacea of the eyelids)
• Corneal or conjunctival foreign body
• Trichiasis (misdirected eyelashes)
• Keratitis / corneal ulcer
• Iritis / anterior uveitis - severe reflex blepharospasm
• Conjunctivitis

Important: Spasms from ocular inflammation persist even after topical anaesthetic application - a key clinical differentiator from purely reflex blepharospasm.

B. Drug-Induced (Tardive Dystonia)

• Antipsychotics (phenothiazines, butyrophenones) - tardive dyskinesia / tardive dystonia
• Neuroleptics - long-term use
• Dopamine antagonists
• Blepharospasm is a recognized form of medication-induced acute or tardive dystonia

C. Neurological / Basal Ganglia Disorders

D. Cerebrovascular Disease

• Cerebral infarction or hemorrhage - especially in the days following stroke; more commonly with left hemisphere (non-dominant) lesions
• Thalamomesencephalic infarct - homolateral blepharospasm
• Bilateral infarctions of rostral brainstem, diencephalon, or striatum
• Left frontal cortical infarction - asymmetric blepharospasm
• Non-dominant striatal infarctions - bilateral transient blepharospasm

E. Demyelinating Disease

• Multiple sclerosis - brainstem plaques involving the rostral brainstem

F. Other Neurological/Systemic Causes

• Retinal degeneration
• Familial apoceruloplasmin deficiency
• Familial syndrome with dystonia and pigmentary retinopathy
• Paraneoplastic midbrain encephalitis
• Autoimmune disease (e.g., systemic lupus erythematosus)
• Myasthenia gravis (can mimic essential blepharospasm through lid fatigue)

G. Functional (Psychogenic)

• Rarely, blepharospasm has a functional basis - eye closure with lid fluttering in suggestible patients
• Psychiatric causation is not supported for essential blepharospasm - psychotherapy and biofeedback have failed to help
• Functional cases are distinguished by suggestibility and inconsistency of findings

Key Distinguishing Features: Blepharospasm vs. Mimics

Precipitating / Aggravating Factors (for essential blepharospasm)

• Bright light (photophobia very common)
• Stress
• Reading and watching television
• Relieved by: talking, relaxation, touching the face, singing, and sleep

Obesity and Recent Advances in Management

Definition & Classification

Pathophysiology

Energy Imbalance & Adipose Dysfunction

• Free fatty acid (FFA) overabundance: Expanded adipose tissue releases FFA excessively → FFA impairs insulin-mediated glucose uptake in muscle, increases hepatic glucose and triglyceride production, and drives VLDL secretion
• Leptin resistance: In obesity, leptin (the adipokine that suppresses appetite and promotes energy expenditure) loses its signaling efficacy ("leptin resistance") - so the normal appetite-braking mechanism fails
• Insulin resistance: Central to metabolic syndrome. The inhibition of lipolysis by insulin is the most sensitive pathway - once this fails, a vicious cycle of lipolysis → FFA excess → worsening insulin resistance ensues

Hormonal Regulation of Appetite

• GLP-1 (glucagon-like peptide-1): incretin released from intestinal L-cells; suppresses appetite via hypothalamus, slows gastric emptying, stimulates insulin, inhibits glucagon
• GIP (glucose-dependent insulinotropic polypeptide): synergizes with GLP-1 for insulin release and adipose metabolism
• Amylin / PYY / CCK: satiety hormones reduced or dysfunctional in obesity
• Ghrelin: "hunger hormone" from stomach - elevated in states of caloric restriction, blunted after surgery

Complications of Obesity

• Cardiovascular: coronary artery disease, heart failure (HFpEF), hypertension, stroke (2-3× risk)
• Metabolic: type 2 diabetes, dyslipidemia, metabolic syndrome, NAFLD/MASLD
• Respiratory: obstructive sleep apnea, obesity hypoventilation syndrome
• Musculoskeletal: osteoarthritis
• Cancer: endometrial, breast, colorectal, esophageal, pancreatic, kidney
• Psychosocial: depression, reduced quality of life

Management Framework: Two Approaches

1. BMI-Centric (NHLBI) Stepwise Model

2. Complications-Centric (AACE) Model

• Stage 0 (no complications): prevent weight gain; lifestyle only
• Stage 1 (mild-moderate complications): lifestyle + obesity medication
• Stage 2 (serious complications): lifestyle + medication + consider bariatric surgery

Pillar 1: Lifestyle Intervention

• Caloric deficit of 500-750 kcal/day
• High-intensity comprehensive lifestyle intervention (behavioral counseling, dietary change, physical activity)
• Goal: ≥5% weight loss to improve metabolic parameters; ≥10% for more significant comorbidity improvement
• Physical activity: ≥150 min/week moderate intensity; ≥200-300 min/week for weight maintenance

Pillar 2: Pharmacotherapy

FDA-Approved Anti-Obesity Medications (AOMs)

Pillar 3: Bariatric / Metabolic Surgery

• BMI ≥40, OR
• BMI 35-40 with serious comorbidity (especially uncontrolled T2DM), after failed medical management
• Some guidelines now consider BMI ≥35 with or without comorbidities

• T2DM remission in 29-43% after RYGB vs. 5-7% with medical therapy alone (ARMMs-T2D study)
• Retinopathy risk reduced by 71%, ESRD by 69%, nephropathy by 59%
• Reduction in hypertension, dyslipidemia, cardiovascular mortality, and obesity-associated cancers
• ~70% of patients achieve success; most weight loss in first 1-2 years
• Operative mortality <0.5% at expert centers

Recent Advances (2023-2026)

1. Semaglutide (Ozempic/Wegovy) - The Benchmark Shift

• Weekly subcutaneous 2.4 mg: 14.9% average weight loss over 68 weeks (STEP trials)
• SELECT trial (2023): In people with obesity and established CVD (no diabetes), semaglutide reduced major adverse cardiovascular events (MACE) by 20% - the first anti-obesity drug to show cardiovascular mortality benefit
• This positioned GLP-1 RAs as disease-modifying rather than just weight-loss agents

2. Tirzepatide (Mounjaro/Zepbound) - Dual Incretin Agonist

• GIP + GLP-1 dual receptor agonist (once weekly SC injection)
• SURMOUNT trials: Mean weight loss of -22.5% at 72 weeks (15 mg dose) in people without diabetes - the largest drug-induced weight loss ever recorded in a phase 3 trial
• FDA-approved for obesity (2023)
• Placebo-subtracted difference: −19.2% vs. −12.9% with semaglutide in meta-analysis (Sabiston Textbook, 2024)
• Weight regain of ~two-thirds within 1 year if stopped - indicating need for chronic therapy

3. Oral Semaglutide 50 mg

• The only oral GLP-1 RA to complete a phase 3 trial (OASIS 1): ~15% weight loss
• Eliminates need for injections - major adherence advantage
• Phase 3 data now available; awaiting broader regulatory approval for obesity indication

4. Pipeline: Triple Agonists and Next-Generation Agents

5. GLP-1 RAs in New Indications (2024-2026)

• Heart failure (HFpEF): Semaglutide improves functional capacity and QoL in HFpEF regardless of diabetes status (STEP-HFpEF trial)
• MASLD/NASH: Tirzepatide up to 20.9% weight change with NASH resolution in phase 3; semaglutide global phase 3 trial ongoing
• Obstructive sleep apnea: Tirzepatide reduces AHI by ~63% (SURMOUNT-OSA, 2024)
• Kidney disease: SELECT and FLOW trial data confirm GLP-1 RAs slow CKD progression

6. Endoscopic Approaches (Emerging)

• Intragastric balloons: 6-month placement, reasonable option for BMI >30; more weight loss than lifestyle alone
• Endoscopic sleeve gastroplasty: suturing stomach into sleeve shape endoscopically; ~15-17% weight loss
• Duodenojejunal bypass liners: impermeable liner excludes proximal small bowel; under investigation
• Aspiration therapy: data still insufficient for routine use per Goldman-Cecil

7. GLP-1 RA Use Perioperatively

• Post-bariatric patients with inadequate weight loss benefit from semaglutide (mean additional 10% weight loss at 12 months, >60% achieving >10%)
• GLP-1 RAs are now used to "bridge" high-BMI patients to surgery as well as adjuvant post-surgery therapy

Choosing Between Options

"Physicians should consider their patients' comorbid conditions and preferences to tailor treatment for each individual."