Phrynoderma case sheet
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phrynoderma follicular hyperkeratosis nutritional deficiency
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I now have comprehensive information from three authoritative dermatology textbooks plus clinical images. Here is the complete Phrynoderma case sheet:
PHRYNODERMA - CLINICAL CASE SHEET
1. DEFINITION & ETYMOLOGY
Phrynoderma (Greek: phrynos = toad + derma = skin) is a nutritional deficiency disorder characterized by follicular hyperkeratosis producing a "toad-skin" appearance. It was first described by Lucius Nicholas in 1933 when he observed hyperkeratotic folliculitis with night blindness and xerophthalmia in East African workers.
2. ETIOLOGY & PATHOGENESIS
Although classically attributed solely to Vitamin A deficiency (VAD), phrynoderma is most accurately a disorder of multiple nutritional deficiencies:
| Deficiency | Role |
|---|---|
| Vitamin A (retinol) | Primary; required for normal keratinization of mucosal and skin surfaces |
| B-complex vitamins | Contributing deficiency |
| Vitamin C | Can mimic phrynoderma (also causes follicular hyperkeratosis) |
| Vitamin E | Contributing deficiency |
| Essential Fatty Acids (EFAs) | Contributing deficiency |
| Protein-Energy Malnutrition (PEM) | General malnutrition state |
Mechanism: Vitamin A is required for normal keratinization of mucosal and skin surfaces. Deficiency leads to abnormal keratinization, squamous metaplasia of glandular epithelia, and follicular plugging.
Vitamin A sources: Retinyl esters in milk, fish oil, liver, and eggs; carotenoids in plants.
3. EPIDEMIOLOGY & RISK FACTORS
- Common in children in the developing world (where VAD is prevalent)
- Rare in developed countries - seen in specific settings:
- Intestinal malabsorption (bariatric surgery, Crohn disease, IBD, celiac disease)
- Pancreatic insufficiency
- Cystic fibrosis
- Liver disease
- Anorexia nervosa / fad diets
- Long-term parenteral nutrition without adequate supplementation
4. CLINICAL FEATURES
Skin Lesions
Two morphological types of follicular papules:
| Type | Size | Description |
|---|---|---|
| Small papules | 1-2 mm | Closely resemble keratosis pilaris |
| Large, diagnostic papules | 2-6 mm | Crateriform, filled with central keratotic plug - may simulate a perforating disorder |
Individual lesion morphology:
- Firm, pigmented (skin-colored to hyperpigmented) acuminate papules
- Central intrafollicular keratotic plug projecting as a horny spine
- Leaves a pit when expressed
- Usually asymptomatic
- Surrounding and arising from pilosebaceous follicles
Distribution (sequential spread):
- Starts: anterolateral thighs / posterolateral upper arms (elbows in 84% in one study)
- Spreads to: extensor surfaces of upper and lower extremities, shoulders
- Then: abdomen, back, buttocks
- Finally: face and posterior neck
Spared areas: Hands, feet, axillary/anogenital regions, midline trunk (occasionally)
Additional cutaneous features:
- Generalized dryness (xerosis) and fine scaling
- Hyperpigmentation
- On face: resembles acne (large comedones) but differs by dryness of skin
- Large dome-shaped nodules on elbows and knees with surrounding red/brown rim
- Hair casts may be seen
Clinical Images
Phrynoderma: follicular hyperkeratotic papules on the abdomen in a patient with IBD (Andrews' Diseases of the Skin)
Typical perifollicular hyperkeratosis of the chest in a Tanzanian adult male (Fitzpatrick's Dermatology)
5. OCULAR FEATURES (Vitamin A Deficiency)
Eye findings in VAD are prominent and often pathognomonic:
| Finding | Notes |
|---|---|
| Nyctalopia (night blindness) | Earliest finding - delayed dark adaptation |
| Xerophthalmia | Dryness of the conjunctiva |
| Bitot spots | Triangular, well-defined white spots on conjunctiva lateral to cornea; apex toward canthus |
| Xerosis cornae | Corneal dryness |
| Keratomalacia | Severe - corneal ulceration/necrosis; major cause of blindness in developing world children |
6. OTHER SYSTEMIC FEATURES
- Squamous metaplasia of salivary glands and nasal/oral mucosa: xerostomia, hyposmia, hypogeusia
- Laryngeal, bronchial, vaginal mucosal involvement
- Mild VAD: xerosis and scaling
- Severe VAD: deep skin fissuring (dermomalacia)
- Increased mortality risk from diarrhea and pneumonia (especially in measles) - VAD impairs gut and lung epithelial integrity
7. HISTOPATHOLOGY
| Finding | Details |
|---|---|
| Hyperkeratosis | Prominent |
| Follicular plugging | Horny plugs in upper hair follicle |
| Coiled hairs | In upper portion of follicle |
| Sebaceous gland atrophy | Severe |
| Eccrine sweat gland metaplasia | Squamous metaplasia of secretory cells |
| Perifollicular granulomas | If follicles rupture |
Note: The "deficiency dermatitis" histologic findings (seen in zinc, EFA, amino acid deficiencies) are NOT features of Vitamin A or Vitamin C deficiency.
8. DIFFERENTIAL DIAGNOSIS
| Condition | Distinguishing Features |
|---|---|
| Keratosis pilaris | No nutritional deficiency; smaller papules; no systemic features |
| Lichen spinulosus | Grouped plaques; usually children; no nutritional deficiency |
| Scurvy (Vitamin C deficiency) | Prominent perifollicular hemorrhage; gingival disease; bleeding tendency |
| Keratosis follicularis (Darier disease) | Genetic; greasy papules; mucous membrane involvement; nail changes |
| Keratosis follicularis spinulosa decalvans | Genodermatosis; scarring alopecia |
| Keratosis circumscripta | Age 3-5 yrs; Africans; well-circumscribed grouped folliculocentric papules on elbows/knees |
| Follicular ichthyosis | Early childhood onset; head and neck predominant |
| Lichen scrofulosorum | Associated with TB; perifollicular granulomas; responds to anti-TB therapy |
| Follicular atopic dermatitis | Atopic background; pruritus; IgE elevation |
| Pityriasis rubra pilaris (juvenile) | Orange-red hue; palmoplantar keratoderma |
| Perforating disorder | Distinguished histologically |
9. INVESTIGATIONS
| Investigation | Relevance | Normal Values |
|---|---|---|
| Serum retinol (Vitamin A) | Confirms VAD; primary test | 20-50 mcg/dL |
| Deficiency | < 20 mcg/dL (< 0.70 μmol/L) | |
| Relative Dose-Response (RDR) test | Oral retinoil glucuronide given; ≥20% rise in serum retinoic acid indicates low liver VA reserves | Newer adjunctive test |
| Serum B-complex vitamins | Assess co-existing deficiencies | - |
| Serum Vitamin C, E | Assess co-existing deficiencies | - |
| Serum EFA levels | If malabsorption suspected | - |
| CBC, serum proteins | Assess nutritional status overall | - |
| Liver function tests | Rule out hepatic malabsorption | - |
| Skin biopsy | Confirms histologic pattern when diagnosis uncertain | - |
10. TREATMENT
Definitive Treatment
- Oral Vitamin A: 100,000 IU/day for 2-3 days, followed by recommended daily requirement
- Since phrynoderma is multifactorial, replace all deficiencies simultaneously (vitamins A, B-complex, C, E, EFAs) - this leads to rapid improvement
Recommended Daily Allowances (Vitamin A)
| Population | RDA |
|---|---|
| Adult females | 700 mcg retinol equivalents |
| Adult males | 900 mcg retinol equivalents |
| Children with measles | 200,000 IU/day x 2 days (also prevents blindness) |
Monitoring
- Serum retinol levels monitored to assess adequacy and avoid toxicity
- Vitamin A toxicity risk: doses as low as 25,000 IU/day in adults with hepatic compromise
Topical Measures (adjunctive)
- Emollients and keratolytics for xerosis and scaling
- Topical retinoids (supportive)
11. PROGNOSIS
- Excellent with correction of nutritional deficiencies
- Skin lesions resolve rapidly with supplementation
- Ocular complications (keratomalacia, blindness) are largely irreversible if not treated early
- Underlying malabsorptive disorder must be addressed to prevent recurrence
12. KEY POINTS FOR EXAMINATION
- Phrynoderma = "toad skin" - follicular hyperkeratosis from nutritional deficiency
- Most common cause: Vitamin A deficiency, but usually multiple deficiencies (A, B, C, E, EFAs)
- Earliest ocular sign of VAD: nyctalopia (night blindness / delayed dark adaptation)
- Pathognomonic eye sign: Bitot spots (triangular conjunctival plaques)
- Earliest skin site: anterolateral thighs and posterolateral upper arms
- Histology: follicular hyperkeratosis + sebaceous gland atrophy + squamous metaplasia of eccrine glands
- Treatment: Vitamin A 100,000 IU/day x 2-3 days + correct all deficiencies
- Distinguish from scurvy: scurvy has perifollicular hemorrhage; phrynoderma does not
- Rare in developed countries - look for malabsorption syndromes as underlying cause
Sources: Andrews' Diseases of the Skin, 12e | Fitzpatrick's Dermatology, 9e | Dermatology 2-Volume Set, 5e (Bolonia)
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