Anterolateral leg alopecia: common but commonly ignored.

A middle-aged man presented with anterolateral leg alopecia which is a very common but under-recognized hair loss condition.

INTRODUCTION

Anterolateral leg alopecia is very common in middle-aged and elderly men but may also occur in women. A previous study estimates the prevalence of anterolateral leg alopecia among males as high as 35%.[1] It often presents as symmetrical, sharply demarcated hair loss confined to the anterior and lateral aspects of both legs. This pattern of hair loss is extremely common yet hardly described in the medical literature.[12] Anterolateral leg alopecia is frequently referred to as peroneal alopecia as the hair loss occurs in the distribution of the superficial branch of the peroneal nerve.

CASE REPORT

A 46-year-old man presented with a 2-year history of reducing hair density affecting the lower legs. There was no history of trauma preceding the onset of hair loss. He has male pattern hair loss and was taking tetracycline as required for rosacea. He was otherwise well with no known allergies. On further questioning, he reported no other body hair loss, rashes or associated symptoms. There was no loss of libido, or erectile dysfunction to suggest androgen deficiency. He has no family history of hair loss or autoimmune disease. The patient had been treated with topical antifungals and topical steroids prior to referral with no improvement.

Physical examination revealed nonscarring hair loss confined to the anterolateral area of lower legs bilaterally [Figure 1]. There were no signs of active inflammation. Dermoscopic examination showed no broken or exclamation mark hairs. His feet were warm with good peripheral pulses. He has classic Norwood-Hamilton Grade IV male pattern hair loss.

Figure 1

Nonscarring hair loss confined to the anterolateral area of lower legs bilaterally

Based on the history and clinical findings, the patient was diagnosed with anterolateral leg alopecia. He was reassured about the benign nature of this condition with no further treatment was given. Diagnostic skin biopsy was declined.

DISCUSSION

Anterolateral leg alopecia was first described in the 1920s[3] yet the cause of this hair loss pattern remains to be elucidated. Leg crossing, trouser rubbing and friction have all been suggested as contributing to this condition though a causal relationship has yet to be confirmed by any studies. Robertson suggested an association between anterolateral leg alopecia and male pattern hair loss.[4] However, Hamilton subsequently demonstrated no statistically significance association between the two conditions.[5] Peripheral vascular disease and thyroid dysfunction are also cited as potential causative factors.[2]

The histopathology features of anterolateral leg alopecia were first described by Gupta and Shaw[2] who showed that specimens lacked hair follicles, but were otherwise unremarkable. The course of this condition has been described as benign and progression appears rare. Spontaneous resolution may occur,[2] but no treatment has been shown to be effective in stimulating hair regrowth. Patient education and reassurance are usually adequate.

The main differential diagnosis of anterolateral leg alopecia is alopecia areata, which typically affects other body areas and displays characteristic dermoscopic and histopathology findings.

CONCLUSION

We report a patient with anterolateral leg alopecia. This distinctive pattern of hair loss is confined to the lower legs and predominantly occurs in male patients. This case highlights a common, benign but under-recognized hair loss condition with surprisingly scanty available information on cause, pathogenesis, course and treatment.