Table 1: Classification of conditions associated with longitudinal melanonychia. Table adapted from J. Andre, N. Lateur. Pigmented nail disorders [2].

Melanonychia

Melanocytic activation

Physiologic causes
 Racial melanonychia
 Pregnancy

Local and regional causes
 Repeated local trauma from poor footwear or overriding toes
 Onychotillomania
 Nail biting
 Occupational trauma
 Carpal tunnel syndrome

Dermatologic causes
 Onychomycosis
 Chronic paronychia
 Psoriasis
 Lichen planus
 Amyloidosis
 Chronic radiation dermatitis
 Systemic lupus erythematosus
 Localized scleroderma
 Onychomatricoma
 Bowen’s disease
 Myxoid pseudocyst
 Basal cell carcinoma
 Subungual fibrous histiocytoma
 Verruca vulgaris
 Subungual linear keratosis

Systemic causes
 Endocrine disorders (Addison’s disease, Cushing’s syndrome,
 Nelson’s syndrome, hyperthyroidism, and acromegaly)
 Alcaptonuria
 Nutritional disorders
 Hemosiderosis
 Hyperbilirubinemia
 Porphyria
 Graft versus host disease (lichen planus-type changes
 accompanied by longitudinal melanonychia)
 AIDS

Iatrogenic causes
 Phototherapy
 X-ray exposure
 Electron beam therapy
 Drug intake*—please see Table 2

Syndromes
 Laugier-Hunziker syndrome
 Peutz-Jegher syndrome
 Touraine syndrome

Melanocytic hyperplasia

Lentigo

Nevus
 Congenital nevi
 Acquired nevi

Nail apparatus Insitu and invasive melanoma