Monilethrix (also referred to as beaded hair) is a rare

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in au ...

dominant hair disease that results in short, fragile, broken

hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and f ...

that appears beaded. It comes from the Latin word for

necklace A necklace is an article of jewellery that is worn around the neck. Necklaces may have been one of the earliest types of adornment worn by humans. They often serve Ceremony, ceremonial, Religion, religious, magic (illusion), magical, or Funerary ...

(''monile'') and the Greek word for hair (''thrix''). Hair becomes brittle, and breaks off at the thinner parts between the beads. It appears as a thinning or baldness of hair and was first described in 1897 by Walter Smith

Signs and symptoms

Some indicators of monilethrix are small bumps on the skin, mainly on the scalp, neck and arms. In most cases, firm, dark papules, covered with dark scales and crusts appears on the skin, especially the scalp. The affected individual would have beaded hair strands. The possible areas for the hair loss are the eyebrows, eyelashes, limbs, and pubic region. Hair strands are usually dull, dry, and brittle. The strands are prone to mild to severe breakage, causing onset alopecia, especially during pregnancy. Fingernail and toenails tend to appear abnormal. The onset for this disease varies from person to person. The frequency of monilethrix is currently unknown.

Presentation

Newborns are not born with Monilethrix; it usually develops within the first few months of life. The presentation may be of

alopecia Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scar ...

(baldness). Individuals vary in severity of symptoms. Nail deformities may also be present as well as

hair follicle The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between h ...

keratosis Keratosis (from '' kerat-'' + '' -osis'') is a growth of keratin on the skin or on mucous membranes stemming from keratinocytes, the prominent cell type in the epidermis. More specifically, it can refer to: * actinic keratosis (also known as solar ...

and follicular

hyperkeratosis Hyperkeratosis is thickening of the stratum corneum (the outermost layer of the epidermis, or skin), often associated with the presence of an abnormal quantity of keratin,Kumar, Vinay; Fausto, Nelso; Abbas, Abul (2004) ''Robbins & Cotran Pathologi ...

. Depending on severity it can effect hair on all areas of the body including head hair, arm and leg hair, pubic hair, underarm hair, eyebrows, and eyelashes. The hair is seen under a microscope with bumps in the hair strand. These cause the hair to be brittle and break in the thinner sections. Severe cases of monilethrix can also effect finger and toe nails causing abnormal growth. Monilethrix can also cause

keratosis pilaris Keratosis pilaris (KP; also follicular keratosis, lichen pilaris, or colloquially chicken skin) is a common, autosomal- dominant, genetic condition of the skin's hair follicles characterized by the appearance of possibly itchy, small, goosefle ...

(small bumps on the skin). Less severe cases of Monilethrix may only affect certain parts of the scalp, usually the back of the head and neck.

Diagnosis

Monilethrix may be diagnosed with

trichoscopy Trichoscopy is a method of hair and scalp evaluation and is used for diagnosing hair and scalp diseases. The method is based on dermoscopy. In trichoscopy hair and scalp structures may be visualized at many-fold magnification. Currently magnificat ...

and other forms of

dermoscopy Dermatoscopy also known as dermoscopy or epiluminescence microscopy, is the examination of skin lesions with a dermatoscope. It is a tool similar to a camera to allow for inspection of skin lesions unobstructed by skin surface reflections. The de ...

. Light microscopic examination is diagnostic and reveals elliptical nodes of normal thickness and intermittent constrictions, internodes at which the hair easily breaks. Under examination, the hair is beaded. The beading is the result of a periodic narrowing of the shaft with nodes separated by about 0.7 mm. In general, there is a tendency for spontaneous improvement with time, especially during puberty and pregnancy, but the condition never disappears completely.

Genetics

Monilethrix is caused by mutations affecting the genes KRTHB1 (

KRT81 Keratin, type II cuticular Hb1 is a protein that in humans is encoded by the ''KRT81'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation ...

), KRTHB3 (

KRT83 Keratin 83, also known as KRT83, is a protein which humans is encoded by the ''KRT83'' gene. Function The protein encoded by this gene is a member of the keratin gene family. As a type II hair keratin, it is a basic protein which heterodimeri ...

), or KRTHB6 (

KRT86 Keratin, type II cuticular Hb6 is a protein that in humans is encoded by the ''KRT86'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation ...

) which code for type II hair cortex

keratins Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...

. The disorder is inherited in an autosomal dominant manner. This means that the defective gene(s) responsible for the disorder is located on an

autosome An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in au ...

, and only one copy of the gene is sufficient to cause the disorder, when inherited from a parent who has the disorder. If an affected parent and an unaffected parent have children, 75% of the time they will be affected by Monilethrix. It can be equally present in both males and females.

Treatment

No specific treatment exists for monilethrix. Spontaneous resolution following puberty has occurred in some cases. In affected females, the condition improves during pregnancy. Genetic counseling will be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.

Epidemiology

Currently, the frequency for this disease is unknown and affects both men and women. Signs and symptoms either show up spontaneously at birth or around the age of 2. The symptoms may change or remain the same throughout one's life, but are usually present after the first few months after birth.

References

External links

{{Cytoskeletal defects Conditions of the skin appendages Autosomal dominant disorders Rare diseases Cytoskeletal defects Human hair Hair diseases