Lichen planus (LP) in families is uncommon. The prevalence of familial LP in a large series has been reported to be 1.5%.1 Since 1970, there have been 10 case reports/studies describing familial LP in 28 families. These case reports of familial LP occurring in two or more members of one family have described cutaneous or a combination of cutaneous and mucosal lesions.2–8 The present case report describes a woman, her son, and grandson with mucosal LP and no cutaneous lesions. To my knowledge, a familial occurrence of mucosal LP in three successive generations has not been reported previously.
A 65-year-old woman (Case 1) presented with complaints of soreness of the mouth of 10 years’ duration. She experienced discomfort and a burning sensation on consuming hot and spicy food. On examination, she had a violaceous plaque of 2.0 × 1.5 cm in size in the middle of the right half of the tongue (Fig. 1). She did not have cutaneous, nail, or scalp lesions. A clinical diagnosis of LP was confirmed on histopathology of the lesion, which showed characteristic parakeratosis, basal cell vacuolar degeneration, and a dense upper dermal infiltrate comprising predominantly lymphocytes. One year later, the 32-year-old son (Case 2) of Case 1 presented with a moderately itchy, violaceous papule on the glans penis of 6 months’ duration and multiple painful violaceous lesions on the buccal mucosa bilaterally. Around the same time, the 11-year-old grandson (Case 3) of Case 1 and the son of Case 2 presented with an erythematous, painful lesion with a violaceous hue, measuring 1.0 × 1.5 cm in size, on the right half of the tongue (Fig. 1) of 2 months’ duration. Histopathology from the lesions was consistent with a clinical diagnosis of LP in Cases 2 and 3. All three patients were treated with topical betamethasone dipropionate 0.05% in gel formulation for a duration of 3–6 months. This treatment resulted in the resolution of the lesions with postinflammatory hyperpigmentation in all three cases. Other members of the family were also clinically examined, but none were found to have mucosal or cutaneous lesions of LP.
The pedigree (Fig. 2) of this family suggests an autosomal dominant transmission, as mucosal LP manifested in one female and two males over three successive generations with each affected individual having an affected parent. In the earlier case reports of familial LP, only two generations were affected, and hence the pattern of inheritance could not be ascertained. The etiopathogenesis of LP remains obscure. Immunologic, infective, and genetic etiologies have been suggested. Copeman et al.2 found an association of human leukocyte antigen (HLA)-B7 in familial cases, but not in patients with sporadic LP; however, no significant associations were found between HLA and LP in other studies.8,9 A single case report described LP concurrently in monozygotic twin sisters, supporting a possible genetic predisposition.10 The present report of mucosal LP in three successive generations also suggests a genetic predisposition to the disease.