Random Dermatology MCQ - Clouston syndrome

A 10-year-old child presents with sparse, brittle, slow-growing scalp hair, along with severe nail dystrophy characterized by thickened, discolored, and prematurely broken nails. The skin is dry but there is no ichthyosis or palmoplantar keratoderma. The child's mother and maternal grandfather have similar hair and nail findings. What is the most likely diagnosis and its mode of inheritance?

A. Clouston syndrome (hidrotic ectodermal dysplasia), autosomal dominant inheritance.
B. Papillon-Lefèvre syndrome, autosomal recessive inheritance.
C. Pachyonychia congenita, autosomal dominant inheritance.
D. Ellis-van Creveld syndrome, autosomal recessive inheritance.
E. Cartilage-hair hypoplasia, autosomal recessive inheritance.

Correct Answer: A. Clouston syndrome (hidrotic ectodermal dysplasia), autosomal dominant inheritance.

Answer and Explanation

The correct answer is A. This question describes the classic features of Clouston syndrome, also known as hidrotic ectodermal dysplasia. The key triad is: 1) Hair abnormalities (sparse, fine, brittle scalp hair, often with sparse eyebrows/eyelashes), 2) Severe nail dystrophy (thickened, discolored, slow-growing, prone to infection), and 3) Normal sweating and normal dentition. This differentiates it from the more common hypohidrotic ectodermal dysplasia (HED). The positive family history with male-to-male transmission supports an autosomal dominant inheritance pattern, which is characteristic of Clouston syndrome.

Why the Other Options are Incorrect:

• B. Papillon-Lefèvre syndrome: This is characterized by severe palmoplantar keratoderma and periodontitis leading to premature loss of deciduous and permanent teeth. Hair and nail changes are not primary features.

• C. Pachyonychia congenita: This features severe, painful palmoplantar keratoderma and grossly thickened nails (pachyonychia), often with oral leukokeratosis. While nails are affected, the hair is typically normal, and the keratoderma is a defining feature absent in Clouston syndrome.

• D. Ellis-van Creveld syndrome: This is a chondroectodermal dysplasia characterized by short limbs, polydactyly, congenital heart defects, and fine, sparse hair. Nail dystrophy can occur, but the skeletal abnormalities are the hallmark.

• E. Cartilage-hair hypoplasia: This is an autosomal recessive disorder featuring short-limbed dwarfism due to metaphyseal chondrodysplasia, fine, sparse hair, and immune deficiency. Nail dystrophy is not a consistent feature.

Additional High-Yield Information for Exams:

• Genetics: Caused by mutations in the GJB6 gene, which encodes connexin 30, a gap junction protein. Inheritance is autosomal dominant.

• Clinical Features:

  • Hair: Alopecia of variable severity, from diffuse thinning to complete absence of scalp hair, eyebrows, and eyelashes. Hair is brittle and breaks easily.

  • Nails: Dystrophy is often the most disabling feature. Nails are thickened (hyperkeratotic), discolored (yellow-brown), striated, and grow slowly. They are prone to recurrent paronychia and fungal infections.

  • Skin: May be dry but is otherwise normal. No anhidrosis/hypohidrosis – patients sweat normally, hence "hidrotic."

  • Teeth: Normal.

  • Other: Palmoplantar keratoderma may occur in some adults but is not a major feature.

• Differential Diagnosis: The main differential is other ectodermal dysplasias. The presence of normal sweating and dentition with severe nail dystrophy is the key to distinguishing Clouston from Hypohidrotic Ectodermal Dysplasia (HED), which features hypohidrosis, hypodontia, and fine hair, but relatively normal nails.

• Associated Conditions & Prognosis:

  • Prognosis: This is a non-progressive, non-life-threatening condition. Lifespan is normal. The main morbidity is cosmetic and functional disability related to the hair and nail changes, and recurrent nail infections.

• Management & Rationale:

  • Rationale: Management is entirely supportive and symptomatic, aimed at improving appearance and function.

  • First-line: Reassurance and genetic counseling. Confirming the diagnosis can relieve anxiety about more severe syndromes.

  • Hair Management: Gentle hair care, wigs or hairpieces if desired.

  • Nail Management: This is the most challenging aspect. Regular podiatric/dermatologic care for debridement of thickened nails. Aggressive treatment of fungal (onychomycosis) and bacterial (paronychia) infections. In severe cases, surgical nail avulsion or matrixectomy may be considered.