Trichostasis Spinulosa: A Case Report with an Unusual Presentation

Trichostasis spinulosa (TS) is a disorder of hair follicle characterized by dark, spiny hyperkeratotic follicular papules which commonly locally distribute on the face or extremities [1]. Breast, scalp, lower eyelid, and axillary areas were reported as uncommon affected sites [2-5]. However, extensive involvement of the disease has rarely been reported.

A 57-year-old male patient visited an outpatient dermatology clinic for the treatment of chronic eczema. Apart from the chief complaint, numerous dark-brownish keratotic follicular papules were noticed at the entire back without being concerned by the patient (Fig. 1). He reported that the lesions at the back developed since his teenage years without any symptoms. None of his family members had similar lesions. He denied waxing, scrubbing, or applying any topical medications. The dermoscopic examination demonstrated a bundle of short, multiple hairs surrounded by a keratinous sheath in a dilated follicle (Fig. 2).

Skin biopsy was performed at a representative area, which revealed follicular hyperkeratosis with dilated infundibulum containing a group of vellus hair shafts (Fig. 3). Based on the history, clinical presentation, and histopathological findings, the diagnosis was consistent with TS. His treatment comprised twice-daily 10% urea cream applied on the lesions, and mild improvement was shown at a 4-week follow-up visit.

TS is a follicular disorder characterized by a cluster of short, successive telogen hairs surrounded by keratinous sheath embedded in the same follicular opening. It was first described as “Pinselhaar” (paintbrush hair) by Franke in 1901. Later, Noble introduced the term “trichostasis spinulosa” in 1913 [6]. Clinically, pinhead-sized hyperkeratotic papules are found at the tip of the nose, cheek, extremities, and interscapular area without gender difference. Most of them are asymptomatic, but sometimes they appear to have pruritus, scaling, and erythema. The differential diagnosis of TS includes keratosis pilaris, pili multigemini, and eruptive vellus hair cyst [7-12]. The clinical, dermoscopic, and histopathological features of these diseases are summarized in Table 1.

In 2002, Strobos and Jonkman [13] have proposed two clinical variants of TS including classical variant and pruritic variant. The classical variant manifests with an asymptomatic comedone-like lesion usually located on the face and often seen in the elderly. On the contrary, the pruritic variant, mostly found in adolescence, manifests with multiple itchy follicular papules on the trunk and extremities [13]. However, the proposed classification could not well describe all reported clinical features.

The etiology of this skin disorder remains inconclusive. Some theories believed that the ceased hair shedding by hyperkeratosis of the hair follicle and the abnormal angulation between the isthmus and the infundibulum are the leading causes of TS [14, 15]. Factors that contribute to follicle damage are congenital dysplasia of the hair follicles and external factors, including ultraviolet light, dust, oils, heat, topical minoxidil, chronic renal failure, Malassezia yeast, Propionibacterium acne, whichalso have been proposed [1, 9, 14, 16].

In the literature review, an extensive presentation of TS has been once reported in a patient with chronic renal failure who had widespread lesions over the body [14]. This condition disappeared after the patient underwent kidney transplantation. However, the disease recurred within 1 week with the same presentation. Our patient also demonstrated extensive TS with an unusual distribution over the entire back. The overlooked nature of these lesions could be explained by their asymptomatic nature, which leads to an ignorance of the disease.

Several treatment modalities have been reported in the literature, including topical keratolytic agents, emollients, hydroactive adhesive pads, and tretinoin solution; however, their effects are usually temporary [17, 18]. Other reported treatments include 800-nm diode laser, which shows 90% complete clearance of the lesions, short-pulsed 755-nm Alexandrite laser, which can cure all patients in the study without recurrence in 3 months, and long-pulsed 755-nm Alexandrite laser, which diminishes more than 50% of lesions in 51% of patients [19-21]. Nevertheless, none of these were noted as a curative treatment.

In conclusion, we report a case of TS with an unusual presentation to emphasize to the physicians the need to pay more attention to this common skin disorder. TS may be unrecognized, and most of the cases are discovered incidentally in patients who visit a hospital with other skin conditions. Furthermore, the dermoscopic examination is inexpensive but proven to be an effective method for the diagnosis of TS.

The patient provided written informed consent to perform all necessary investigations, to take clinical photographs, and use them for research purposes and publication. The patient understood that his name and initial will not be published and due efforts will be made to conceal his identity. This case report was conducted ethically in accordance with the World Medical Association Declaration of Helsinki.

The authors have no conflicts of interest to declare.

The authors have no funding sources to declare.

All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for the manuscript, take responsibility for the integrity of the work as a whole, and have given final approval to the version to be published.