An episodic form of supraventricular tachycardia with abrupt onset and termination.

A slower than normal heart rate (in adults, slower than 60 beats per minute).

Absence of the eyebrow.

Decreased number of hairs per unit area of skin of the scalp.

Hidrotic ectodermal dysplasia 2, or Clouston syndrome (referred to as HED2 throughout this GeneReview) is characterized by a triad of major clinical features including partial-to-complete alopecia, nail dystrophy, and palmoplantar hyperkeratosis. Sweating is preserved and there are usually no dental anomalies. Sparse scalp hair and dysplastic nails are seen early in life. In infancy, scalp hair is fine, sparse, and brittle. Progressive hair loss may lead to total alopecia by puberty. The nails may be milky white in early childhood; they gradually become dystrophic, thick, and distally separated from the nail bed. Palmoplantar keratoderma may develop during childhood and increases in severity with age. Associated features may include cutaneous hyperpigmentation (particularly over the joints) and finger clubbing. The clinical manifestations are highly variable even within the same family.

Onychodystrophy (nail dystrophy) refers to nail changes apart from changes of the color (nail dyschromia) and involves partial or complete disruption of the various keratinous layers of the nail plate.

Nail that appears thick when viewed on end.

Decreased density/number of eyelashes.

A lesser degree of hair pigmentation than would otherwise be expected.

Reduced number or density of pubic hair.

Reduced number or density of axillary hair.

Decreased length of the eyelashes (subjective).