NORD gratefully acknowledges Gill Chao, NORD Editorial Intern from the Emory University Genetic Counseling Training Program and Cecelia A. Bellcross, PhD, MS, CGC, Associate Professor, Director, Genetic Counseling Training Program, Emory University School of Medicine, for assistance in the preparation of this report.
Keratosis follicularis spinulosa decalvans (KFSD) is a rare, inherited, skin disorder. KFSD is characterized by hardening of the skin (keratosis) on several parts of the body. Most frequently, the face, neck, and forearms are involved. The thickening of the skin is accompanied by the loss of eyebrows, eyelashes and beard. Baldness (alopecia) usually occurs. People with KFSD may have reduced tolerance to bright light (photophobia), inflammation of the eyelids (blepharitis), and inflammation of the outer membrane of the eyeball and the inner eyelid (conjunctivitis, also known as pink eye). Some have abnormal accumulation of material in the clear outer layer of the eye (corneal dystrophy), which may cause loss of vision or blurred vision. Some may also have poor fingernail formation.
Most affected families with KFSD demonstrate an X-linked recessive inheritance pattern. This form of KFSD is called X-linked keratosis follicularis spinulosa decalvans (KFSDX). KFSDX affects predominately men in the family, while women have much milder symptoms. KFSD in these families is caused by an alternation in the MBTPS2 gene. Some studies suggest that an alternation in the SAT1 gene causes this form of KFSD as well.
KFSD is a type of ichthyoses, a group of inherited disorders of the skin in which the skin tends to be thick and rough and has a scaly appearance. Hardening of the skin around the hair follicles leads to scarring and baldness. This condition begins in infancy, initially appearing on the face and neck, and then progresses to the chest, back, abdomen, arms and legs. Hair loss of the eyebrows and scalp caused by the scarring become evident in childhood and progress until teenage years.
Allergic reactions (atopy), photophobia, and inflammation of the eye’s cornea (keratitis) may also occur. Some people have itchy and red eyeballs and eyelids. Some people affected with KFSD have corneal dystrophy. The cornea must remain clear to be able to focus incoming light. Therefore, corneal dystrophy may cause blurred vision or loss of vision. Occasionally, the teeth become stained and fingernails are poorly formed.
The word decalvans comes from the Greek for snake and alludes to the whorls and winding streaks characteristic of the pattern of baldness in this disorder. The name is often accompanied by the phrase “cum ophiasi” which simply means baldness.
Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
KFSD is usually caused by an alternation in the MBTPS2 gene. Some studies suggest that an alternation in the SAT1 gene causes this form of KFSD as well. This form of KFSD is called X-linked keratosis follicularis spinulosa decalvans (KFSDX) and follows an X-linked recessive inheritance pattern.
X-linked genetic disorders are conditions caused by an abnormal gene on the X chromosome and manifest mostly in males. Females that have an abnormal gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms because females have two X chromosomes and only one carries the abnormal gene. Males have one X chromosome that is inherited from their mother and if a male inherits an X chromosome that contains an abnormal gene he will develop the disease.
Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease and a 25% chance to have an unaffected son.
If a male with an X-linked disorder is able to reproduce, he will pass the abnormal gene to all of his daughters who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring.
Some families with KFSD are reported to have male to male transmission, which suggests autosomal dominant inheritance. In these families, sons inherited KFSD from their father. All males in the family are affected by KFSD. All females do not have KFSD. The gene that causes KFSD in these families is not known.
Rarely, patients with KFSD do not have any family history of KFSD. More research is needed to understand what gene causes KFSD in these families.
KFSD is a rare disorder affecting males more severely than females. Because some people with KFSD may go unrecognized or undiagnosed, determining the true frequency of these disorders in the general population is difficult. KFSD is estimated to affect about less than 1 in 1,000, 000 people in the general population.
In most instances, the appearance of the skin determines the diagnosis, but a family history and physical examination are often required to rule out other possible causes of scaly, dry skin. Some physicians may examine skin tissue under a light microscope or even under an electron microscope.
Molecular genetic testing can confirm a diagnosis of KFSDX. Molecular genetic testing looks for changes or alterations in the MBTPS2 and SAT1 genes known to cause KFSDX. A negative genetic test result does not rule out KFSD.
The dry scaly skin of KFSD is relieved by applying skin softening (emollient) ointments to soften add moisture the skin. This can be especially effective after bathing while the skin is still moist. Plain petroleum jelly is preferable. Lactate lotion can also be effective. Salicylic acid gel is another particularly effective ointment. The skin should be covered at night with an airtight, waterproof dressing when this ointment is used.
Drugs derived from vitamin A (retinoids) such as tretinoin, motretinide, and etretinate are often effective against symptoms of ichthyosis. They are help produce a thinner outermost layer of the skin and smooth the skin. Retinoids should never be taken except under the supervision of a doctor, and under strict guidelines, as outlined by the FDA and the drug manufacturers. This is because it can cause toxic effects on the bones in some patients. A synthetic derivative of vitamin A, isotretinoin, when taken orally by pregnant women, can cause severe birth defects in the fetus. The decision to treat with systemic retinoids requires consultation with a physician experienced in their use for these conditions.
People with KFSD should follow-up with an eye doctor (ophthalmologist) for monitoring and treating symptoms of eye problems and watch for symptoms of pink eye and blurred or declining vision.
In general, dietary changes have little or no effect on the ichthyoses. Although retinoids are used to treat ichthyosis, taking vitamin A in excess of normal daily requirements is not recommended. Excess vitamin A is toxic and can result in cerebral edema (swelling of the brain) and damage to the liver. Children can be particularly sensitive to toxic amounts of vitamin A.
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