Onychomadesis is characterized by the detachment of the nail plate from the proximal nail fold with persistent attachment to the nail bed and often, but not always, eventual shedding and is due to a severe insult that produces a complete arrest of nail matrix activity [
6]. Most commonly, onychomadesis has been reported in association with pemphigus vulgaris and hand–foot–mouth disease, and following chemotherapy or antiepileptic medications [
2,
6].
MMP is a chronic autoimmune sub-epithelial blistering disease of the mucous membranes and, less often, the skin. The primary lesion is a vesicle or bulla, and this evolves to become an erosion or ulcer that heals with scarring [
7,
8]. Autoantibodies binding to the epithelial basement membrane zone (BMZ) have been demonstrated in this subset, targeting bullous antigens 1 and 2, laminin 332 and laminin 311, type VII collagen, alpha 6 beta 4 integrin, and some nonidentified basal membrane zone antigens [
5]. Diagnosis of MMP can be done based on clinical features, histopathological study, and immunopathological (direct and indirect immunofluorescence) and immunochemical studies. Distinction from other subepidermal autoimmune bullous diseases depends on clinical presentation with predominant mucosal involvement [
7]. Both lesional skin and mucosal biopsies in our patient demonstrated subepithelial and subepidermal blister formation with underlying mixed inflammatory cell infiltrate, which is consistent with pemphigoid disorders [
7]. Direct immunofluorescence (DIF) testing was found to be unexpectedly negative. The diagnosis of MMP depends largely on DIF testing, which is known to be the gold standard [
7]. However, many studies conducted on patients with MMP showed DIF sensitivity rates of 70–80% [
9‐
11]. In those studies, MMP diagnosis in patients with negative DIF was formed based on clinical and histopathological features. Sinclair et al. [
12] demonstrated that all target antigens found in the normal non-appendageal basement membrane, in specific the epidermal-associated antigens 220-kDa and 180-kDa BP antigens, were expressed by the proximal nail fold, the nail matrix, the nail bed and the hyponychium. Nail abnormalities are rarely involved in pemphigoid disorders. One report described nail dystrophy and ptergyium formation in a patient with MMP [
3]. Onychomadesis was also reported in a patient with BP [
13].
The paronychia described in our patient was chronologically associated with the disease activity and has cleared after controlling the symptoms, therefore, suggesting a possible association.
In conclusion, we report a case of onychomadesis following an episode of acute paronychia in a patient with MMP. We believe it is important for dermatologists to be aware of this association to avoid additional investigations or treatments.