Vitamin A Deficiency

Overview

Plain-Language Overview

Vitamin A deficiency is a condition where the body lacks enough vitamin A, an essential nutrient important for maintaining healthy vision, skin, and immune function. People with this deficiency may experience problems seeing in low light or at night, a symptom known as night blindness. The skin can become dry and rough, and the eyes may develop dryness or more serious damage. This condition is more common in areas where diets lack sufficient vitamin A or in people with certain medical problems that affect nutrient absorption. Without enough vitamin A, the body's ability to fight infections can also be weakened.

Clinical Definition

Vitamin A deficiency is a clinical condition characterized by insufficient levels of retinol and its derivatives in the body, leading to impaired function of multiple organ systems. It primarily affects the visual system, causing symptoms such as night blindness and xerophthalmia, which includes conjunctival and corneal dryness and keratomalacia. The deficiency results from inadequate dietary intake, malabsorption syndromes, or increased metabolic demand. Biochemically, it is marked by low serum retinol concentrations, typically below 0.70 µmol/L. The deficiency disrupts the normal function of rhodopsin in retinal photoreceptors, impairing dark adaptation. Additionally, vitamin A is crucial for maintaining epithelial integrity and immune competence, so deficiency can lead to increased susceptibility to infections and skin changes like follicular hyperkeratosis. Chronic deficiency may cause irreversible blindness and increased childhood mortality. Diagnosis involves clinical assessment and laboratory measurement of serum retinol, with consideration of underlying causes such as malnutrition or liver disease.

Inciting Event

Dietary deficiency due to inadequate intake of vitamin A-rich foods.
Onset of a malabsorption disorder impairing vitamin A absorption.
Increased vitamin A demand during infection or pregnancy.

Latency Period

Symptoms typically develop after months to years of inadequate vitamin A intake.

Diagnostic Delay

Early symptoms like night blindness are often subtle and overlooked.
Lack of awareness about vitamin A deficiency in non-endemic areas.
Misattribution of ocular symptoms to other eye diseases.

Clinical Presentation

Signs & Symptoms

Night blindness (nyctalopia) as an early symptom due to impaired rod function.
Dryness of the conjunctiva and cornea (xerophthalmia).
Bitot spots on the conjunctiva.
Increased susceptibility to infections due to impaired mucosal immunity.
Dry, scaly skin and follicular hyperkeratosis.

History of Present Illness

Progressive difficulty seeing in dim light or at night (night blindness).
Dryness and irritation of the eyes, with possible development of Bitot spots (foamy conjunctival plaques).
In severe cases, complaints of eye pain and vision loss due to corneal ulceration or keratomalacia.

Past Medical History

History of malabsorption syndromes such as cystic fibrosis or celiac disease.
Previous episodes of chronic diarrhea or gastrointestinal surgery.
Chronic liver disease affecting vitamin A storage and metabolism.

Family History

None typically relevant as vitamin A deficiency is not inherited.

Physical Exam Findings

Presence of Bitot spots, which are foamy, triangular, gray-white patches on the conjunctiva.
Dry, rough skin due to xerosis caused by impaired epithelial differentiation.
Corneal keratomalacia, characterized by softening and ulceration of the cornea.
Night blindness evidenced by delayed adaptation to darkness during eye examination.

Diagnostic Workup

Diagnostic Criteria

Diagnosis of vitamin A deficiency is based on clinical signs such as night blindness, xerophthalmia, and keratomalacia, combined with laboratory evidence of low serum retinol levels below 0.70 µmol/L. Additional findings may include follicular hyperkeratosis and increased susceptibility to infections. A thorough dietary history and assessment for malabsorption or liver disease are essential to identify underlying causes.

Pathophysiology

Key Mechanisms

Vitamin A deficiency impairs the production of rhodopsin, a pigment essential for low-light vision, leading to night blindness.
Deficiency disrupts the maintenance of epithelial tissues, causing keratinization and dryness, particularly in the conjunctiva and cornea.
Lack of vitamin A reduces the function of the immune system, increasing susceptibility to infections.

Involvement	Details
Organs	Eye is the primary organ affected, with symptoms including xerophthalmia and night blindness.
	Liver stores vitamin A and is involved in its metabolism and mobilization.
	Skin may show dryness and hyperkeratosis due to impaired epithelial maintenance.
Tissues	Epithelial tissue integrity is compromised in vitamin A deficiency causing keratinization and dryness.
Tissues	Retinal tissue is affected leading to impaired photoreceptor function and night blindness.
Cells	Conjunctival epithelial cells are affected in vitamin A deficiency leading to xerosis and keratinization.
	Rod photoreceptor cells in the retina require vitamin A derivatives for normal function and night vision.
	Goblet cells in the conjunctiva decrease in number causing reduced mucin production and dry eyes.
Chemical Mediators	Retinoic acid acts as a signaling molecule regulating gene expression for epithelial cell differentiation.
Chemical Mediators	11-cis-retinal is the chromophore in rhodopsin essential for phototransduction in rod cells.

Treatment

Pharmacological Treatments

Vitamin A supplementation
- Mechanism: Replenishes retinol stores to restore normal epithelial cell function and vision
- Side effects: headache, nausea, dizziness, increased intracranial pressure

Non-pharmacological Treatments

Increase dietary intake of vitamin A-rich foods such as liver, dairy products, and orange or green leafy vegetables.
Implement public health measures like food fortification and nutrition education to prevent deficiency.
Ensure adequate breastfeeding in infants to provide natural vitamin A.

Prevention

Pharmacological Prevention

Oral vitamin A supplementation with high-dose retinyl palmitate or retinyl acetate.
Periodic vitamin A dosing in high-risk populations to prevent deficiency.

Non-pharmacological Prevention

Dietary diversification to include vitamin A-rich foods such as liver, dairy products, and orange/yellow vegetables.
Breastfeeding promotion to provide infants with adequate vitamin A.
Public health measures to reduce malnutrition and improve sanitation.

Outcome & Complications

Complications

Corneal ulceration and keratomalacia leading to blindness.
Increased risk of severe infections due to compromised mucosal barriers.
Permanent visual impairment if untreated.

Short-term Sequelae	Long-term Sequelae
Night blindness causing difficulty seeing in low-light conditions. Conjunctival xerosis and Bitot spots formation. Increased frequency of infections due to impaired immunity.	Permanent blindness from corneal scarring and keratomalacia. Chronic dry eye syndrome leading to corneal damage. Growth retardation and impaired immune function in children.

Differential Diagnoses

Vitamin A Deficiency versus Congenital Stationary Night Blindness

Vitamin A Deficiency	Congenital Stationary Night Blindness
Night blindness develops later due to nutritional deficiency.	Night blindness is present from birth or early childhood without progression.
Bitot spots and conjunctival xerosis are present in vitamin A deficiency.	Normal conjunctiva without Bitot spots or xerosis.
ERG is typically normal in vitamin A deficiency.	Electroretinogram (ERG) shows characteristic abnormalities.

Vitamin A Deficiency versus Keratoconjunctivitis Sicca (Dry Eye Syndrome)

Vitamin A Deficiency	Keratoconjunctivitis Sicca (Dry Eye Syndrome)
Night blindness is a prominent symptom in vitamin A deficiency.	Dryness and irritation of the eyes without night blindness.
Bitot spots and corneal changes are specific to vitamin A deficiency.	Schirmer test shows decreased tear production.
Tear production is usually normal in vitamin A deficiency.	No Bitot spots or corneal ulceration related to vitamin deficiency.

Vitamin A Deficiency versus Vitamin A Deficiency

Vitamin A Deficiency	Vitamin A Deficiency
Night blindness is an early and characteristic symptom.	Night blindness is typically absent in early stages.
Bitot spots (foamy, white conjunctival plaques) are a hallmark sign.	Bitot spots on the conjunctiva are not present.
Xerophthalmia with corneal dryness and potential ulceration occurs in advanced deficiency.	Xerophthalmia and corneal ulceration are uncommon.