Vitamin A Deficiency

Vitamin A deficiency (VAD) is a classic nutritional and metabolic disorder with far-reaching effects on keratinocyte differentiation, mucosal structure and skin barrier function. Biologically active retinoids, especially retinoic acid, are essential signals for keeping epidermal cell division and differentiation in balance. Without enough vitamin A, the skin develops abnormal hyperkeratinization, and the lining of glands and hair follicles undergoes squamous metaplasia.

Clinically, the most striking and characteristic skin sign of VAD is phrynoderma (“toad skin” follicular hyperkeratosis). It comes with severe dry skin (xerosis), reduced sebum production, slow wound healing and a higher risk of secondary skin infection. Spotting these skin changes early is key to heading off other dangerous systemic complications, particularly damage to vision: dry eyes, Bitot’s spots, night blindness and eventually blindness.

At Haute-Derma, our VAD workup is comprehensive: serum retinol measured by high-performance liquid chromatography (HPLC) and dermatoscopy to distinguish the different follicular keratinization disorders, followed by systemic vitamin A replacement according to WHO standards and topical keratolytic and lipid barrier–restoring treatment.

Pathophysiology and Molecular Mechanisms in the Skin

Causes and Disrupted Nuclear Receptor Signaling

Disrupted RAR/RXR signaling:
- Normally, retinoic acid binds to the nuclear receptor complex formed by RAR (retinoic acid receptor) and RXR (retinoid X receptor), regulating the genes that control the keratinocyte cycle.
- When vitamin A is lacking, this signaling breaks down. Keratinocytes in the epidermis and the follicular neck can no longer differentiate normally, resulting in hyperkeratosis and dense keratin plugs in the follicle openings.
Squamous metaplasia of sebaceous and sweat glands:
- The secretory lining of sebaceous and sweat glands is replaced by keratinizing squamous epithelium.
- Sebaceous glands shrink and produce less sebum, severely weakening the skin’s natural protective lipid film. Transepidermal water loss (TEWL) rises sharply, causing widespread dry skin (xerosis).
Impaired dermal renewal and slow wound healing: VAD reduces fibroblast activity and the production of type I and III collagen and glycosaminoglycans in the dermis. The skin becomes thin, fragile and less elastic, and wounds are slow to re-epithelialize.

Skin Manifestations

Phrynoderma (“Toad Skin” Follicular Hyperkeratosis)

Appearance: Numerous pointed, cone-shaped keratotic papules 1–3 mm across, each with a hard central keratin plug in the follicle (keratotic follicular plugs). The skin feels rough, like a nail file or a toad’s skin.
Typical locations: Usually symmetrical on the extensor surfaces of the limbs (elbows, knees, thighs), buttocks, shoulders and trunk. In severe cases it can spread to the neck and face.
Course: The plugs may come out, leaving small pits at the follicles, sometimes with perifollicular hyperpigmentation.

Severe Dry Skin with Fine Scaling (Xerosis Cutis)

The whole skin becomes rough, dull and grayish, losing its natural sheen.
Fine, powdery or small fish-like scales flake off here and there, with mild to moderate itch caused by loss of the epidermal lipid barrier.

Weakened Skin Immunity and Secondary Infection: Because the mucosa and skin barrier are cracked, bacteria (Staphylococcus aureus) and yeasts (Candida) get in easily, causing pustular folliculitis, impetigo or persistent infected dermatitis.

Associated Eye and Systemic Signs

Eyes: Night blindness (the earliest sign), conjunctival dryness, Bitot’s spots (foamy gray-white patches on the conjunctiva), corneal dryness and corneal softening (keratomalacia).
General: Greater susceptibility to respiratory and gastrointestinal infections, and stunted growth in children.

Diagnosis at Haute-Derma

Haute-Derma follows a standard medical workup to confirm VAD and distinguish it from other keratinization disorders:

Serum micronutrient levels and biochemistry:
- Serum retinol (HPLC):
  - Normal: 30–65 µg/dL (1.05–2.27 µmol/L).
  - Deficiency (VAD): < 20 µg/dL (< 0.7 µmol/L).
  - Severe deficiency: < 10 µg/dL (< 0.35 µmol/L).
- Measurement of retinol-binding protein (RBP) and prealbumin to assess vitamin A transport.
Dermatoscopy: Shows raised yellow-gray keratin plugs in the follicle openings, surrounded by faint redness or hyperpigmentation, with loss of the normal capillary pattern.

Telling Follicular Keratinization Disorders Apart:

Condition	Markers and Cause	Distinguishing Clinical Features
Phrynoderma (VAD)	Serum retinol < 20 µg/dL; poor intake or absorption	Hard keratotic papules with central plugs on the extensor surfaces of the limbs, with severe dry skin and night blindness/dry eyes.
Keratosis pilaris (KP)	Inherited (often with atopic dermatitis); NORMAL serum retinol	Faint red or pink bumps on the outer upper arms and thighs; no eye involvement and no severe generalized dryness.
Darier disease	ATP2A2 gene mutation; autosomal dominant	Greasy, malodorous gray-brown keratotic papules in seborrheic areas (chest, back); nails with red/white longitudinal bands and V-shaped notches.
Lichen spinulosus	Cause unknown; local immune reaction	Follicular keratotic papules appearing suddenly in symmetrical round patches or clusters on the trunk and limbs.

Medical Treatment and Skin Barrier Repair

Treating VAD combines correctly dosed systemic vitamin A with topical keratolytic and barrier-repair therapy:

Systemic Vitamin A Supplementation (WHO Standard)

Treatment dose for adults and children over 1 year: 200,000 IU retinyl palmitate (or retinyl acetate) by mouth on day 1 and day 2, with the same dose repeated 2 weeks later.
Fat malabsorption (cirrhosis, short bowel syndrome, biliary obstruction): Water-miscible intramuscular vitamin A (50,000–100,000 IU/day) as prescribed by a specialist.

Topical Treatment and Skin Barrier Repair

Loosening keratin plugs (keratolytic therapy): A keratolytic cream with 3–5% salicylic acid, 10–20% urea or 12% lactic acid applied once or twice daily softens and releases the keratin plugs in the follicles.
Topical retinoids (vitamin A derivatives): Tretinoin 0.025–0.05% or adapalene 0.1% applied every evening helps normalize keratinocyte differentiation locally and flattens phrynoderma lesions faster.
Rebuilding the epidermal lipid barrier: An intensive moisturizer with a physiological ceramide:cholesterol:essential fatty acid ratio plus 5% D-panthenol quickly restores the stratum corneum lipid layer, lowers TEWL and relieves dryness.

Frequently Asked Questions (FAQs)

+How is phrynoderma from vitamin A deficiency different from ordinary keratosis pilaris?

Both conditions produce similar follicular keratotic bumps, but keratosis pilaris (KP) is a common, harmless inherited condition limited to the outer upper arms and thighs, with completely normal blood vitamin A levels. Phrynoderma is caused by a micronutrient deficiency: it is more widespread (elbows, knees, buttocks, trunk), serum retinol is markedly low, and it always comes with severe dry skin, mucosal changes or night blindness.

+Can high-dose vitamin A for phrynoderma cause toxicity?

When the medical VAD regimen is followed correctly (200,000 IU on the first 2 days, repeated after 2 weeks), the risk of toxicity is very low because the liver’s stores are depleted. However, taking high-dose vitamin A on your own for long periods (> 50,000 IU/day for months) can cause chronic vitamin A toxicity, with the opposite picture: peeling dry skin, severe scaly cheilitis, diffuse hair loss, raised intracranial pressure and liver damage.

+Why are people with liver, biliary or pancreatic disease prone to vitamin A deficiency even with a normal diet?

Vitamin A is fat-soluble and needs bile salts and pancreatic lipase to be emulsified and absorbed in the small intestine. Once absorbed, it is stored mainly in the liver (80–90%) as retinyl esters and travels in the blood bound to retinol-binding protein (RBP), which the liver makes. Patients with cirrhosis, chronic pancreatitis, biliary obstruction or malabsorption therefore cannot properly emulsify, store or transport vitamin A, and develop secondary VAD even when their intake is adequate.

+After vitamin A treatment, how long does it take for phrynoderma bumps and dry skin to clear?