What's Your Diagnosis?
Skin-Colored Papules on the Chest
An otherwise healthy male presents with multiple smooth uniform painless cystic papules scattered across his central chest.
Diagnosis
Based on the timing and characteristics of her nail detachment, the patient was diagnosed with onychomadesis, which is defined as painless detachment of the proximal nail plate from the nail matrix and nail bed after at least 40 days from an initial insult. Air beneath the detached nail plate causes a characteristic creamy-white discoloration. The severity of onychomadesis ranges from transverse furrows that affect a single nail without shedding, known as Beau lines, to multiple nails that are completely shed.1,2 Nail plate shedding is typical because the nail matrix, the site of stem cells and the most proximal portion of the nail apparatus, is damaged and transiently arrested.
Various etiologies can halt nail plate production abruptly within the matrix. These typically manifest ≥ 40 days after the initial insult (the length of time for a fingernail to emerge from the proximal nail fold).2 The annual incidence of these etiologies ranges from approximately 1 per 1 million people for Stevens-Johnson syndrome, a rare cause of onychomadesis, to 1 per 10 people for onychomycosis, one of the more common causes of onychomadesis.3 The Table compares the characteristics of the diagnoses that are most commonly associated with nail detachment and discoloration.
When a single nail is affected, the etiology of onychomadesis usually is primary and local, including mechanical nail trauma and fungal nail infections (onychomycosis).1,2 Candida onychia is onychomycosis caused by Candida species typically Candida albicans, which result in localized nail darkening, chronic inflammation of the paronychial skin, and cuticle loss. The infection favors immunocompromised people; coinfections are common, and onychomadesis or onycholysis can occur. Unlike onychomadesis, onycholysis is defined by painless detachment of the distal nail plate from the nail bed, but nail shedding typically does not occur because the nail matrix is spared. The preferred treatment for Candida onychia is oral itraconazole, and guided screenings for immunodeficiencies and endocrinopathies, especially diabetes mellitus, should be completed.3,4
Tinea unguium is another form of onychomycosis, but it is caused by dermatophytes, typically Trichophyton rubrum or Trichophyton mentagrophytes, which produce white and yellow nail discoloration followed by distal to proximal nail thickening and softening. Infection usually begins in toenails and demonstrates variable involvement in each nail as well as asymmetric distribution among digits.3 This condition also may eventuate in onychomadesis or onycholysis. Debridement followed by oral terbinafine is the treatment of choice.4
Two other causes of localized nail discoloration with or without nail detachment include melanonychia and nail bed infection by Pseudomonas aeruginosa (P aeruginosa). Melanonychia can be linear or diffuse brown discoloration of 1 or more nails caused by melanin deposition. Either pattern is a common finding in dark-skinned people, especially by age 50 years, but melanocyte hyperplasia should be excluded in all individuals along with drug adverse effects, exogenous pigments, infections, and systemic diseases.3,5 P aeruginosa produces pyocyanin, the green pigment responsible for the discoloration seen in this opportunistic infection often localized to a single nail. Prior maceration of the nail apparatus by repeated water submersion is common among affected individuals. Avoidance of submerging fingernails in liquids followed by nail debridement and oral antipseudomonal antibiotics is the preferred treatment course.3
The etiology is usually secondary and systemic when multiple nails demonstrate onychomadesis, but the exact pathophysiology is poorly understood. One of the most studied infectious etiologies of onychomadesis is hand-foot-and-mouth disease (HFMD), which typically affects children aged < 10 years. Parents often will recall their child being ill 1 to 2 months prior to the nail findings. Scarlet fever and varicella also can result in onychomadesis. Although not common systemic causes, Stevens-Johnson syndrome and toxic epidermal necrolysis can trigger onychomadesis of multiple nails that usually resolves in several months, but other nail deformities often persist.2,6 Onycholysis also can accompany this finding.7 Autoimmune etiologies of onychomadesis include alopecia areata and pemphigus vulgaris. Inciting medications that are toxic to the nail matrix include chemotherapy agents, valproic acid, carbamazepine, lithium, and azithromycin. Rare congenital disorders and birth trauma also can present with onychomadesis of multiple nails during infancy.2
Systemic etiologies typically affect fingernails more than toenails because of the faster growth rate of fingernails. Once the source of onychomadesis is controlled or eradicated, complete regrowth of fingernails can take from 4 to 6 months. Toenails can take twice as long and older age increases all regrowth periods.5
Our patient was treated with analgesics until her mucosal surfaces fully healed, and topical emollients and keratolytics were used to soften eschars from previous blisters and prevent further scar formation. Her affected fingernails shed and regrew after 6 months without additional interventions.