Acrokeratoelastoidosis typically presents in children and adolescents, usually before the 2nd and 3rd decades of life, although reports do exist of onset in adulthood.[19] Clinically, AKE presents with clusters of multiple asymptomatic, small, round-to-oval, skin-colored/translucent or yellowish firm papules located over the lateral and/or medial margins of hands and/or feet. Papules have a keratotic rough surface and may show a crateriform to umbilicated appearance [Figure 1(A)]. Papular acrokeratosis, a synonym for acrokeratoelastoidosis stems from such characteristic morphology and location of lesions. Involvement of the dorsa of hands/feet is characteristic [Figure 1(B)], qualifying the lesion as 'inverse' papular acrokeratosis.[18][20] Other areas reported to have occasional involvement include - the posteromedial border of the feet and the pre-tibial region.[20] The lesions are typically distributed in a bilateral and symmetrical pattern, although unilateral involvement has been reported.[2][16][21] The papules may coalesce to form plaques.

Typically, except for cosmetic disfigurement, the lesions are asymptomatic in most of the cases. Mild itching, hyperhidrosis, and aquagenic palmoplantar keratoderma constitute uncommon presentations/associations.[3][15] A family history of similar lesions is commonly positive since the majority of cases show an autosomal dominant mode of inheritance. The clinician should inquire about a history of chronic or repeated trauma to palms and soles or excessive sun exposure. Trauma, handwashing, clothes, and irritation from ill-fitting footwear may increase the dimensions of acrokeratoelastoidosis. 

In most cases, the lesions stabilize after a few weeks to months of onset although there are anecdotal reports of rapid progression of lesions during pregnancy.[10]

Dermoscopy

Polarized videodermoscopic evaluation of the affected areas of the thumbs and index fingers shows focal clusters of pale-to-yellowish colored papules with slight umbilication in a few of them, interspersed with pale yellow-colored structureless areas [Figure 1 (C)].

Histopathology

The gold-standard technique of diagnosis of acrokeratoelastoidosis remains histopathology. Apart from various epidermal alterations (vide infra), the presence of a reduced number of thick and fragmented elastic fibers in the dermis ('elastorrhexis') is the diagnostic hallmark; the latter feature is observed even on a routine hematoxylin-eosin (H & E) section [Figure 1 (D)].but better appreciated with special stains for elastin such as Verhoeff’s-Van Gieson (VVG) [Figure 1 (E)], Weigert and Orcein.

Ultrasonography: Doppler Study

In a recent study, the use of Doppler ultrasound (USG) examination was reported to be a useful non-invasive adjuvant investigation for confirmation of diagnosis and benignancy of the condition (lack of protrusions of fat lobules) and ruling out the presence of piezogenic pedal papules and granulomas.[22] In acrokeratoelastoidosis, doppler USG demonstrates several focal solid hypoechoic and hypovascular areas with thickening of the epidermis and upper dermis.[22]

Since the condition is asymptomatic and benign, treatment should focus on patients who are cosmetically concerned. To date, various forms of treatments - topical, oral and surgical/physical have been attempted to improve upon the appearance of AKE-affected acral parts of the patients, but the outcome has been modest to poor. The various treatment modalities tried [3][10][22][10][23][24]:

1. Topical - emollients and keratolytic agents including salicylic acid, urea, sulfur, coal tar, and tretinoin, as well as topical corticosteroids
2. Oral - corticosteroids, antibiotics, dapsone, methotrexate, isotretinoin, acitretin
3. Physical/surgical - cryotherapy with liquid nitrogen, and surgery with laser erbium: yttrium-aluminum-garnet (Er: YAG)

Treatment with oral retinoids, especially acitretin has been suggested as the most effective; however, relapse post-cessation is inevitable[10]

Summarily, even in patients with acrokeratoelastoidosis  offered treatment for cosmetic improvement, three factors merit consideration and require explanation to the patient before commencing treatment:

1. Modest response to be expected
2. If using topicals - indefinite use may be necessary to maintain any improvement
3. If planning oral/systemic therapy - the possibility of an almost inevitable relapse on stoppage of the drug, and the adverse effects of the drug(s)

Differential diagnosis includes conditions considered as members of the family of marginal and acral keratodermas, and other distinctive disorders involving the acral parts with similar appearing lesions. It is important to know that involvement of the borders or palmoplantar transition areas typifies 'marginal keratodermas'; involvement of the dorsum of the hands and feet qualifies the marginal keratoderma to be called 'inverse.'[18]  Some of the important differentials include[3][10][25][22]:

1. Focal acral hyperkeratosis - differentiable on histopathology due to changes limited to the epidermis, with the absence of elastorrhexis
2. Keratoelastoidosis marginalis (also known as Ramos and Silva marginal keratoderma) - associated with intense sun exposure and shows prominent actinic damage
3. Other acral keratoderma variants - hereditary papulotranslucent acrokeratoderma, acrokeratoderma hereditarium punctatum, punctate palmoplantar keratoderma
4. Miscellaneous conditions - acrokeratosis verruciformis of Hopf, degenerative collagenous plaques (of the hands), digital papular calcinosis, verruca plana, primary cutaneous amyloidosis, and mosaic acral keratosis

It is important to reiterate that many forms of PPK, including certain types of PPKP, are harbingers or cutaneous markers of serious underlying morbidity. However, AKE is a benign form of PPKP, with no associated medical condition. Discounting the fact of poor response to treatments and indefinite persistence of lesions, the overall prognosis of the condition is excellent. 

There are no known or reported complications of acrokeratoelastoidosis.

Despite the good prognosis of this condition, many issues trouble the patient and family members, such as the cosmetic disfigurement caused by the papules, persistence of lesions and modest-to-poor response of treatments tried till date for acrokeratoelastoidosis of Costa. Thus, patient and family education about the benignity of the condition constitutes a much more critical component of management than suggesting treatment for cosmetic improvement of the lesions (vide supra). 

Although AKE is a simple clinical diagnosis, it may be logical to get a skin biopsy done followed by re-affirmation of the condition's benign nature. The general perception in the mind of patients of  'biopsy is suggestive of an ominous disorder like a malignancy' is convincingly contradicted with the biopsy report of AKE revealing benign features. Of course, the treating dermatologist's counseling skills constitute an essential part of adequate patient education.

Acrokeratoelastoidosis of Costa is a type of marginal keratoderma that typically affects the borders of palms and soles and frequently involves the dorsum of hands and feet.

In most cases, it is of familial origin with an autosomal-dominant mode of inheritance (although rarely it may be autosomal recessive). However sporadic occurrence is well known.

Clusters of skin-colored to yellowish-brown keratotic papules appear along the borders of hands and feet, typically during the 2nd and 3rd decade of life. The papules often have an umbilicated or crateriform appearance.

Chronic trauma and excessive sun exposure have been proposed as possible exacerbating factors.

Despite the condition's rarity, detections is straightforward based on clinical features alone. However, diagnostic confirmation warrants histopathology. Elastorrhexis, i.e., fragmented elastic fibers in the dermis constitutes the pathological diagnostic hallmark, better appreciated on slides specially stained to highlight elastin such as VVG or Orcein.

Treatment is required only for cosmetic reasons. Attempts with topical corticosteroids, salicylic acid, urea, coal tar, oral acitretin, and surgical techniques including liquid nitrogen cryotherapy, and erbium: yttrium-aluminum-garnet (Er: YAG) laser ablation have all shown only a modest and temporary improvement.

Oral retinoids provide the best improvement, but relapse following cessation of therapy and the potential adverse effects of the systemic therapy for an otherwise benign condition do not support their liberal use.

The most important part of management is patient and family counseling about the benign nature and good prognosis of the condition. 

Owing to the rarity of this genodermatoses, two issues are potentially problematic. Firstly, non-dermatologists' awareness about this condition is very low and needs to be enhanced. This CME activity is a humble attempt towards that. Secondly, the treatment-related evidence for acrokeratoelastoidosis is limited to anecdotal reports only. Since controlled trials seem impractical because of the condition's rarity, small-to-large case series with a single intervention should be the way forward.