**3. Congenital causes of hair loss**

Congenital hair loss is a loss of hair that is present at birth; the following conditions are some of possible causes of congenital hair loss.

#### **3.1. Nevus sebaceous of Jadassohn**

Nevus sebaceous of Jadassohn (**Figure 1**) (also known, as sebaceous nevus) is a yelloworange, waxy, and hairless plaque that typically occurs on the scalp [6]. Such nevi are present

**Figure 1.** This is a 5-year-old male patient presented with yellow plaque, waxy on the scalp without hair growth. This plaque was since birth.

at birth or early childhood as a congenital plaque without hair but at the age of puberty show remarkable overgrowth (due to the activity of sebaceous glands at this age). Hair follicles are not present within the lesion itself, but lesions on the scalp may be covered over by surrounding hair, so careful examination is important. Skin growths such as benign tumors and basal cell carcinoma can arise in sebaceous nevi, usually in adulthood. Rarely, sebaceous nevi can give rise to sebaceous carcinoma.

#### **3.2. Aplasia cutis congenita**

Similar to hair loss in adults [1], this problem can be caused by a number of conditions, but in patterns that are different in frequencies and presentations from those seen in adults. There are common and uncommon causes for this complaint, and this usually covers a broad differential diagnosis [2]. This chapter has been written in an attempt to distinguish the types of hair loss (acquired and congenital, common and uncommon), to facilitate the diagnostic

To fully understand hair loss during childhood, a basic comprehension of normal hair growth is necessary [3, 4]. Generally, at 22 weeks of intrauterine life, the developing fetus has all of its hair follicles formed. At this stage, there are nearly about one million of hair follicles on the

At any given time, a random number of hairs will be in one of three stages of growth and shedding: anagen, catagen, and telogen. Each phase has specific characteristics that determine the length of the hair. All three phases occur simultaneously; one strand of hair may be in the

(A) Lanugo hair is long, unpigmented, and very fine, and the very first hair fiber to be produced is by a hair follicle. As an embryo develops, the hair follicles form and begin to produce this type of hair. This first wave of growth is normally shed by the embryo at around 8 months gestation and replaced by terminal or vellus hair ready for birth. However, sometimes babies can be born with this coat of lanugo hair (called "congenital hypertrichosis lanuginosa").

(B) Vellus is short, fine, unpigmented hair. This type of hair is commonly seen on the nose and

(C) Terminal, it is long, coarse, pigmented, and frequently contains a medulla. During puberty, many hair follicles around the genitals, armpits, beard, and chest in men transform from vellus hair to terminal hair under the direction of hormones. Equally, hormones can cause termi-

Congenital hair loss is a loss of hair that is present at birth; the following conditions are some

Nevus sebaceous of Jadassohn (**Figure 1**) (also known, as sebaceous nevus) is a yelloworange, waxy, and hairless plaque that typically occurs on the scalp [6]. Such nevi are present

head. Hair on the scalp grows about 0.3–0.4 mm/day or about 6 inches/year.

Essentially, there are three basic groups of hair based on hair follicle size [5].

nal hairs to revert to vellus hair production as in androgenetic alopecia.

causes of this problem, and finally to reach a proper treatment.

anagen phase, while another is in the telogen phase.

**3. Congenital causes of hair loss**

of possible causes of congenital hair loss.

**3.1. Nevus sebaceous of Jadassohn**

**2. Normal hair growth**

256 Hair and Scalp Disorders

over the cheeks.

Aplasia cutis congenita (also known as "Cutis aplasia," "Congenital absence of skin," and "Congenital scars") is a heterogeneous group of disorders characterized by the absence of a portion of skin in a localized or widespread area at birth [7, 8]. The defect may involve only the epidermis and upper dermis (localized and noninflammatory defect) resulting in minimal alopecia, or it may extend into the deep dermis, subcutaneous tissue, or rarely periosteum, skull, and dura (especially in the deeper and lager one). This deep and severe form of aplasia cutis can be associated with a neural cranial tube defect (encephalocoele or meningocoele), which can be demonstrated by an ultrasound scan showing misplaced brain tissue outside the skull. It is the most common congenital cicatricial alopecia and manifests as a solitary defect on the scalp in 70% of cases, but it may sometimes occur as multiple lesions. Most lesions of aplasia cutis congenita occur on the scalp vertex just lateral to the midline, but defects may also occur on the face, trunk, or limbs, sometimes symmetrically.

#### **3.3. Ectodermal dysplasia**

Ectodermal dysplasias are described as "heritable conditions in which there are abnormalities of two or more ectodermal structures such as hair, teeth, nails, or sweat gland function, in addition to another abnormality in a tissue of ectodermal origin, e.g., ears, eyes, lips, mucous membranes of the mouth, or nose, central nervous system" [9]. It is not a single disorder, but a group of syndromes. The signs and symptoms of ectodermal dysplasia differ markedly between the different types of the condition and depend on the structures that are affected. Signs and symptoms are not usually apparent in newborns and may not be picked up till infancy or childhood. The affected individuals have abnormalities of the hair follicles (the scalp and body hair may be thin, sparse, and very light in color). The hair may grow very slowly or sporadically, and it may be excessively fragile, curly, or even twisted (**Figure 2**).

#### **3.4. Hair shaft defects**

Hair shaft abnormalities are characterized by changes in color, density, length, and structure [10]. Hair shaft alterations often result from structural changes within the hair fibers and cuticles, which may lead to brittle and uncombable hair.

**Figure 3.** A female child with loose anagen hair syndrome. It is prominent that the hair was relatively sparse and does not grow long. Hair is of fair color, and hair shafts were of reduced caliber.

Hair shaft defects may result in dry and lusterless hair, coarse or fizzy hair, uncombable hair, and fragile hair. Hair shaft diseases may occur as localized or generalized disorders.

#### **3.5. Loose anagen hair syndrome**

between the different types of the condition and depend on the structures that are affected. Signs and symptoms are not usually apparent in newborns and may not be picked up till infancy or childhood. The affected individuals have abnormalities of the hair follicles (the scalp and body hair may be thin, sparse, and very light in color). The hair may grow very slowly or sporadically, and it may be excessively fragile, curly, or even twisted (**Figure 2**).

Hair shaft abnormalities are characterized by changes in color, density, length, and structure [10]. Hair shaft alterations often result from structural changes within the hair fibers and

**Figure 3.** A female child with loose anagen hair syndrome. It is prominent that the hair was relatively sparse and does

**Figure 2.** A child presented with fragile, curly hair since birth; the main complaint was persistent short and fragile hair.

**3.4. Hair shaft defects**

258 Hair and Scalp Disorders

cuticles, which may lead to brittle and uncombable hair.

not grow long. Hair is of fair color, and hair shafts were of reduced caliber.

This child had also cone-shaped teeth and scanty eyebrows.

Loose anagen syndrome is a benign, self-limiting condition where anagen hairs are easily and painlessly extracted and mainly reported in childhood [11]. It can be seen in normal population and in alopecia areata. The hair is relatively sparse and does not grow long. Hair is of fair color and hair shafts of reduced caliber, and an early age of onset are features. Usually, the hairs are not fragile, and there are no areas of breakage (**Figure 3**).
