Keratosis follicularis spinulosa decalvans (KFSD) is a rare X-linked hereditary disorder characterized by the triad of follicular hyperkeratosis-photophobia-alopecia. The clinical heterogeneity makes the diagnosis difficult. To investigate the clinicopathologic and trichoscopic features of KFSD and to further clarify the essential requisites for the diagnosis, we conducted a retrospective study of patients with KFSD. The clinical information, histologic features, and trichoscopic findings were evaluated. Eight patients were from seven separate families. Two females were mother and daughter from the same family and the other six patients were male and represented sporadic cases. The average age of onset of alopecia was 21.25 years. Involvement of the scalp hairs leading to progressive scarring alopecia on the midline of the scalp with variable degrees of inflammation was the pathognomonic feature. It typically began after puberty. Vellus hair-associated follicular hyperkeratosis affected all of the patients. However, photophobia was not a constant feature. Histopathologic examination revealed disorders of the hair follicle with an acute-chronic inflammatory response. Follicular changes including fused infundibulum, the protrusion of the outer root sheath into the follicular canal, and a dilatation of the follicles at the isthmus level caused by the occlusion of keratin were observed. The trichoscopic features included perifollicular scaling, tufted hairs, and loss of follicular openings. In conclusion, terminal hair involvement, either scalp hairs, eyebrows, or eyelashes, and the hyperkeratosis of the follicle of vellus hairs is the diagnostic basis of KFSD. We hypothesize that follicular changes in histopathology are the primary event that trigger variable inflammation and further follicular destruction.

Keratosis follicularis spinulosa decalvans (KFSD) is a rare cornification disorder with an X-linked recessive inheritance in most cases. Pathogenic variants causing X-linked KFSD have been described in MBTPS2, the gene for a membrane-bound zinc metalloprotease that is involved in the cleavage of sterol regulatory element binding proteins important for the control of transcription. Few families have been identified with an autosomal dominant inheritance of KFSD. We present two members of an Austrian family with a phenotype of KFSD, a mother and her son. The disease was not observed in her parents, pointing to a dominant inheritance with a de novo mutation in the index patient. Using whole-exome sequencing, we identified a heterozygous missense variant in CST6 in DNA samples from the index patient and her affected son. In line with family history, the variant was not present in samples from her parents. CST6 codes for cystatin M/E, a cysteine protease inhibitor. Patient keratinocytes showed increased expression of cathepsin genes CTSL and CTSV and reduced expression of transglutaminase genes TGM1 and TGM3. A relative gain of active, cleaved transglutaminases was found in patient keratinocytes compared to control cells. The variant found in CST6 is expected to affect protein targeting and results in marked disruption of the balance between cystatin M/E activity and its target proteases and eventually transglutaminases 1 and 3. This disturbance leads to an impairment of terminal epidermal differentiation and proper hair shaft formation seen in KFSD.

UNASSIGNED: Keratosis follicularis spinulosa decalvans (KFSD) is a rare, X-linked, hereditary disorder of keratinization, characterized by skin involvement and progressive scarring alopecia of scalp, eyebrows, and eyelashes. The diagnosis is helped by the particular clinical features, but pathology is mandatory.
UNASSIGNED: We described a case of a female patient referred to the outpatient\'s hair consultation of our department, in which we performed trichoscopy as a very useful tool for the diagnosis, followed by pathology that confirmed KFSD.
UNASSIGNED: In our article, we underlined the importance of trichoscopy for the diagnosis of this hair disease, with also a review of the literature on diagnosis and treatment.

Keratosis follicularis spinulosa decalvans is a disorder affecting the hair follicles characterized by scarring alopecia of the scalp, eyebrows, and axillae, sometimes associated with photophobia and keratoderma. Being X-linked, it is more commonly seen in males but can be rarely seen in females also. We report three cases of this rare disorder including one in a female.

The diagnosis of disorders of the hair and scalp can generally be made on clinical grounds, but clinical signs are not always diagnostic and in some cases more invasive techniques, such as a biopsy, may be necessary. This 2-part article is a detailed review of the histologic features of the main types of alopecia based on the traditional classification of these disorders into 2 major groups: scarring and nonscarring alopecias. Scarring alopecias are disorders in which the hair follicle is replaced by fibrous scar tissue, a process that leads to permanent hair loss. In nonscarring alopecias, the follicles are preserved and hair growth can resume when the cause of the problem is eliminated. In the second part of this review, we describe the histologic features of the main forms of scarring alopecia. Since a close clinical-pathological correlation is essential for making a correct histopathologic diagnosis of alopecia, we also include a brief description of the clinical features of the principal forms of this disorder.

Keratosis follicularis spinulosa decalvans (KFSD) is an X-linked xenodermatosis characterized by scarring alopecia and follicular hyperkeratosis. This condition mainly affects males with females being carriers and will have milder symptoms. We present two sisters with severe form of KFSD, progressing to scarring alopecia.