Congratulations to the World Champion Eagles – Even the Thinker is Green!
Although I was delighted to learn that topical tacalcitol may resolve a familial occurrence of follicular keratosis of the chin (1), I couldn’t get too excited until I learned what FKC is, having never heard of it prior to this article.
The diagnosis of follicular keratosis of the chin (FKC) first appeared in the literature in 1992, in a report by Kanzaki et al, describing the cases of 7 and 10-year-old boys with noninflammatory, follicular, keratotic “plugs” of the chin. The older child had a family history of atopy. Both boys rested on their chins while reading or watching television. Biopsies from both cases revealed dilated follicles that were filled with keratin; no inflammation was noted. Both cases resolved shortly (weeks to months) after the patients were advised to leave their chins alone. (2)
Virtually immediately, letters appeared stating that this condition had been described previously. Padilha-Gonçalves suggested the term “traumatic anserine folliculosis” in 1977. The “goose skin” of his 11 patients appeared after pressure and friction. Seven of these 11 patients had a history of atopy. (3) Brenner and Bandsen referred to an article they wrote in 1985 describing two brothers with keratotic papules on their chins, induced by watching television with lying with their chins on the carpet. The authors had learned of this condition from an oral presentation at the 4th International Dermatopathology colloquium in 1983. (4) In his reply, Dr. Kanzaki noted that he was not aware of these reports based on his survey of the literature.
All was quiet in the FKC world for 15 years, until Yanagihara et al reported the case of a 6-year-old non-atopic Japanese boy who would rest his chin on the back of his hand when drawing. The decision to treat with topical vitamin D3 was made based on its reported successful use in nevus comedonicus; the improvement was presumably due to vitamin D’s effect on modulating epidermal differentiation (even with therapy, the patient could not leave his chin alone!). The authors also reviewed the literature on FKC; at that time there had been a total of 25 cases in the literature. They noted that therapy with keratolytic agents was unsuccessful. (5)
Buechner et al reported two healthy brothers ages 7 and 5 years with FKC. The lesions were asymptomatic, and the patients denied rubbing their chins. Topical tacalcitol resulted in complete clearance within 4 weeks; the ointment was used for 3 months – there was no recurrence after a year. (1).
A healthy 7-year-old boy with asymptomatic FKC, with no history of trauma to the skin, failed to respond to topical tretinoin. (6)
What can we conclude about FKC? Having never seen a case, it is presumptuous of me to speculate, but I will. My impression it that there are two overlapping types of FKC – 1) familial (due to a keratin mutation?), requiring therapy, such as topical vitamin D; and 2) acquired, secondary to rubbing, possibly more so in patients with an atopic background. Breaking the rubbing habit may be all that is necessary therapeutically in such cases.
In both circumstances, FKC is a benign condition, but should be differentiated from other entities including keratosis pilaris, lichen spinulosis, trichodysplasia spinulosa, follicular mucinosis, and follicular spicules associated with myeloma. A clinical diagnosis should suffice, but if need be biopsies would be helpful in differentiating these conditions. Non-invasive modalities, such as optical coherence tomography, which has been reported to assist the diagnosis of FKC, will be used increasingly in the future.
Rubbing one’s chin is considered body language for thinking before coming to a conclusion. I found myself doing just that when researching this entity. I have not yet observed any keratotic papules!
- Buechner AA, et al. Topical tacalcitol for family occurrence of follicular keratosis of the chin. JAMA Dermatol 2018; 154: 111-2.
- Kanzaki T, et al. Follicular keratosis of the chin. J Am Acad Dermatol 1992; 26: 134-5.
- Padilha-Gonçalves A. J Am Acad Dermatol 1992; 26 (6 Pt 1): 1032.
- Brenner S, Brandsen R. Follicular keratosis of the chin. J Am Acad Dermatol 1992; 26 (6 Pt 1): 1032.
- Yanagihara M, et al. Follicular keratosis of the chin treated with 1.24R-dihydroxyvitamin D3 ointment. Pediatr Dermatol 2007; 24: 412-4.
- Nguyen S, et al. Optical coherence tomography-assisted diagnosis of follicular keratosis of the chin. J Eur Acad Dermatol Venereol 2016; 30: 861-2.
*The clinical image is from Rambhia KD, et al. Traumatic anserine folliculosis. Indian Dermatology Online Journal 2017; 8: 59-61. The image of Rodin’s “The Thinker” is from Wikimedia Commons
Dermatology Insights and Inquiries (DI&I) is the 2017 Recipient of the AAD Sulzberger Dermatologic Institute and Education Grants Committee’s Program for Innovative Continuing Medical Education in Dermatology (PICMED) Grant. The PICMED project and DI&I are funded by an endowment established by the Skin Disease Education Foundation and the Elsevier Foundation.