When we think of common inflammatory disorders psoriasis and eczema may come to mind as very common dermatoses but one condition that is also commonplace is lichen planus (LP) affecting just over 1% of adults [1]. The condition is most common in middle aged adults and is classically characterised by red, polygonal papules. Extreme itching is often the clinical characteristic which helps to point to the diagnosis. Typically lesions occur on the extremities mostly around the wrists and ankles. Dermatoscopically, the condition is characterised by “Wickham’s striae” – white lines criss-crossing like train tracks visible under the lens across the surface of the lesion. The condition, like psoriasis, exhibits the Koebner phenomenon. Because of the intense itching the condition can be particularly distressing for patients. Nail changes can also affect around 10% of patients with LP with splits, ridges and thinning of the nail plate [2]. Under the umbrella of LP, there are many different variants which can manifest as skin or mucosal disease. A full guide can be found within reference [3].
The exact cause of the condition is not known but is likely to be an autoimmune disease. Known triggers include many drugs (listed below) and there is some suggestion that it may be triggered by viral infections [1].
· Angiotensin-converting enzyme inhibitors
· Thiazide diuretic
· Antimalarials
· Anti-inflammatory drugs
· Antimicrobials
· Antihypertensives
· Psychiatric drugs
· Antidiabetics
· Penicillamine
Common Drugs implicated as a triggers for Lichen Planus
As with many conditions, having Lichen Planus may be associated with a greater risk of having other conditions. This is not unusual within medicine or dermatology. For example, patients with psoriasis are at a greater risk of developing cardio-vascular disease, diabetes and dyslipidaemia [4-7]. A recent study published this year undertook a review of two medical databases in the UK and USA to examine possible relationships between LP and other conditions [8]. One of the databases included was the UK Biobank which contains the genetic and medical information of over 500 000 people in the United Kingdom. With a large amount of data, it allows for a detailed analysis of selected conditions. Investigators compared patients within two databanks diagnosed with LP against two control groups with other dermatological conditions.
The results showed that LP commonly occurs alongside other autoimmune (AI) conditions which is not an uncommon finding as many patients with AI disease many have multiple pathologies (vitiligo, psoriasis, lupus and sarcoidosis, for example). In addition, LP patients were more likely to suffer from conditions of the digestive system including the mouth, oesphagus, stomach and intestines along with liver (including cirrhosis and non-alcoholic liver disease). Rates of ulcerative colitis and diverticular disease were also higher in patients with LP than those without.
As the authors point out, this study merely highlights associations and cannot explain the reasons for them. In addition, the data is only as good as the clinicians recording the patient’s health but on the face of it, this work is a good grounding on which further investigations can be made.
Podiatric Implications
LP is a condition which podiatrists are likely to come across as lesions are common on the lower extremity, particularly visible around the ankle. It appears to be more common in patients with diabetes, probably as a result of their medication which is known to be a trigger. The condition can be distressing and is often under treated as it requires the use of potent steroids topically to bring the symptoms under control. For many patients the condition tends to burn itself out, but management of any itching is key to reduce distress. As part of any assessment understanding disease associations is useful to know when patients may report other symptoms which can connect the two diagnoses so an appropriate referral can be made.
Further information about lichen planus can be found online here:
a. Clinical Information from the Primary Care Dermatology Society (https://www.pcds.org.uk/clinical-guidance/lichen-planus)
b. A clinical guide to Lichen Planus (https://onlinelibrary.wiley.com/doi/full/10.1111/ddg.14565)
References
1. Boch, K., et al., Lichen Planus. Front Med (Lausanne), 2021. 8: p. 737813.
2. Friedman, P., et al., Dermoscopic findings in different clinical variants of lichen planus. Is dermoscopy useful? Dermatology Practical & Conceptual, 2015. 5(4): p. 51-55.
3. Solimani, F., et al., Lichen planus – a clinical guide. JDDG: Journal der Deutschen Dermatologischen Gesellschaft, 2021. 19(6): p. 864-882.
4. Christophers, E., Comorbidities in psoriasis. J Eur Acad Dermatol Venereol, 2006. 20(s2): p. 52-55.
5. Brauchli, Y.B., S.S. Jick, and C.R. Meier, Psoriasis and the risk of incident diabetes mellitus: a population-based study. British Journal of Dermatology, 2008. 159(6): p. 1331-1337.
6. Gelfand, J.M., et al., The Risk of Stroke in Patients with Psoriasis. J Invest Dermatol, 2009. 129(10): p. 2411-2418.
7. Yamazaki, F., Psoriasis: Comorbidities. The Journal of Dermatology, 2021. 48(6): p. 732-740.
8. Fromme, M., et al., Comorbidities in lichen planus by phenome-wide association study in two biobank population cohorts*. British Journal of Dermatology, 2022. 187(5): p. 722-729.