Eyelash trichomegaly: review of congenital, acquired, and drug-associated etiologies for elongation of the eyelashes

Eyelash trichomegaly complicating pembrolizumab for colorectal cancer

INTRODUCTION

Pembrolizumab is an immune checkpoint inhibitor widely administered for the treatment of various malignancies. Despite its effectiveness, its distinctive mechanism of action may lead to immune-related adverse events, most frequently affecting cutaneous tissues. Hair-related adverse events, although uncommon, include conditions such as alopecia areata and alterations in hair texture or type.

CASE REPORT

A 63-year-old male patient presented with eyelash trichomegaly following two cycles of pembrolizumab infusion.

TREATMENT AND OUTCOME

The patient experienced discomfort due to the eyelash trichomegaly, prompting him to consider discontinuing the treatment. However, the patient's neoplastic disease demonstrated a complete radiologic response, which encouraged him to continue the therapy.

DISCUSSION

This case illustrates a unique documentation of pembrolizumab-induced eyelash trichomegaly. While immune checkpoint inhibitors like pembrolizumab are known to cause hair-related adverse events, reports of eyelash trichomegaly remain rare. This case emphasizes the necessity for clinicians to remain vigilant about such uncommon side effects to ensure comprehensive patient management.

Trichomegaly induced by topical tacrolimus for the treatment of periorbital vitiligo: A brief report of a new adverse effect

Trichomegaly is a known adverse effect of systemic administration of cyclosporine but is less commonly associated with systemic tacrolimus or with topical calcineruin inhibitors. In this report, we describe the first case, to our knowledge, of trichomegaly due to long-term use of topical tacrolimus for periocular vitiligo.

The eyelash follicle features and anomalies: A review

The primary role of eyelashes is to protect and maintain the health of the lid margin. However, the mechanisms to fulfill this role are not fully understood. Unraveling these mechanisms will stand to greatly improve the efficiency of eye care professionals' interventions in anomalies of the eyelashes. The aim of this article is to provide a review on eyelashes including highlights and new avenues for research; the biology of both the lash and its follicle; the pathophysiology and management of lash anomalies by eye care professionals; and the effect of iatrogenic factors on lashes. Using the database of Ovid MEDLINE, we reviewed studies specifically directed on human/mammalian eyelashes and key articles on current trends in scalp hair methodologies that can be applicable to lash research. The eyelash morphology, pigmentation and growth rate have been documented using techniques ranging from lash imaging to follicle immunohistochemistry. Furthermore, studies have demonstrated that the lash follicle is sensitive to many factors of the external environment, a variety of systemic/topical medications and cosmetics. Recently, aerodynamic studies using a mammalian eye model confirmed that an optimal lash length was needed so that eyelashes serve a protective role in reducing the number of particles that can reach the eye. Despite recent advances in lash research, studies are still scarce, due to the limited availability of the human lid for sampling. This review brings awareness that further research is needed with respect to eyelashes and will hopefully reduce the gap with scalp hair research.

Eyelash length for the diagnosis of atopic dermatitis and ichthyosis vulgaris in children-a case control study

Eyelash trichomegaly (ET) is increased length (≥ 12 mm), curling, pigmentation, or thickness of eyelashes. Among acquired causes, allergic diseases and atopic dermatitis (AD) have been found to be associated with eyelash trichomegaly especially in children; however, to date, this claim has not been studied in detail. To compare the eyelash lengths of AD and ichthyosis vulgaris (IV) patients with those of age- and sex-matched patients with unrelated skin disorders, we measured (with a digital Vernier caliper) and compared the eyelash lengths of AD (n = 58) and IV (n = 31) patients to those of age- and sex-matched patients with unrelated skin disorders (n = 178). The eyelashes of the AD and male IV patients were found to be significantly longer than those of the controls (p < 0.05). The severity of atopic dermatitis, i.e., SCORAD of > 50, hyperlinearity of palms and soles, and high IgE levels significantly correlated with the long eyelashes. The limitations of study are single-center study and filaggrin gene mutation in patients of IV could not be studied.

CONCLUSION

Thus, long eyelashes may act as surrogate marker of severe AD and serve as a cutaneous marker of IV patients. What is Known: • Among acquired causes, allergic diseases and atopic dermatitis have been found to be associated with eyelash trichomegaly especially in children. What is New: • The severity of atopic dermatitis, i.e., SCORAD of > 50, hyperlinearity of palms and soles, and high IgE levels significantly correlate with the long eyelashes; thus, long eyelashes may act as surrogate marker of severe atopic dermatitis. • It may also serve as a cutaneous marker of ichthyosis vulgaris especially in male patients and patients with palmoplantar hyperlinearity.

Trichomegaly Induced by Cetuximab: Case Series and Review the Literature

Trichomegaly is a rare side effect of epidermal growth factor receptor inhibitors. We present here 4 patients who treated with cetuximab (an epidermal growth factor receptor inhibitor) for metastatic colorectal cancer. All of the cases were treated with cetuximab 500 mg/m biweekly in combination protocol. The mean period from the start of the treatment until the development the trichomegaly was 4.75 (3-6) months. In all of the patients after the end of the cetuximab therapy, trichomegaly was regressed. Only 1 case resolved with topical treatment that conjunctivitis with trichomegaly. Trichomegaly is an important ocular toxicity of cetuximab that can cause visual discomfort and corneal damages. However, these side effects usually do not require discontinuation of treatment.

Biology of the eyelash hair follicle: an enigma in plain sight

Because of their crucial impact on our perception of beauty, eyelashes constitute a prime target for the cosmetic industry. However, when compared with other hair shafts and the mini-organs that produce them [eyelash hair follicles (ELHFs)], knowledge on the biology underlying growth and pigmentation of eyelashes is still rudimentary. This is due in part to the extremely restricted availability of human ELHFs for experimental study, underappreciation of their important sensory and protective functions and insufficient interest in understanding why they are distinct from scalp hair follicles (HFs) (e.g. ELHFs produce shorter hair shafts, do not possess an arrector pili muscle, have a shorter hair cycle and undergo greying significantly later than scalp HFs). Here we synthesize the limited current knowledge on the biology of ELHFs, in humans and other species, their role in health and disease, the known similarities with and differences from other HF populations, and their intrinsic interethnic variations. We define major open questions in the biology of these intriguing mini-organs and conclude by proposing future research directions. These include dissecting the molecular and cellular mechanisms that underlie trichomegaly and the development of in vitro models in order to interrogate the distinct molecular controls of ELHF growth, cycling and pigmentation and to probe novel strategies for the therapeutic and cosmetic manipulation of ELHFs beyond prostaglandin receptor stimulation.

FGF5 is a crucial regulator of hair length in humans

Mechanisms that regulate the growth of eyelashes have remained obscure. We ascertained two families from Pakistan who presented with familial trichomegaly, or extreme eyelash growth. Using a combination of whole exome sequencing and homozygosity mapping, we identified distinct pathogenic mutations within fibroblast growth factor 5 (FGF5) that underlie the disorder. Subsequent sequencing of this gene in several additional trichomegaly families identified an additional mutation in FGF5. We further demonstrated that hair fibers from forearms of these patients were significantly longer than hairs from control individuals, with an increased proportion in the growth phase, anagen. Using hair follicle organ cultures, we show that FGF5 induces regression of the human hair follicle. We have identified FGF5 as a crucial regulator of hair growth in humans for the first time, to our knowledge, and uncovered a therapeutic target to selectively regulate eyelash growth.