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What is Palmoplantar keratoderma and explain in detail?
Palmoplantar keratodermas are a heterogeneous group of disorders characterized by abnormal thickening of the stratum corneum of the palms and soles.
Autosomal recessive, dominant, X-linked, and acquired forms have all been described.: 505 : 211

Types
Clinically, three distinct patterns of palmoplantar keratoderma may be identified: diffuse, focal, and punctate.: 505

Diffuse
Diffuse palmoplantar keratoderma is a type of palmoplantar keratoderma that is characterized by an even, thick, symmetric hyperkeratosis over the whole of the palm and sole, usually evident at birth or in the first few months of life.: 505   Restated, diffuse palmoplantar keratoderma is an autosomal dominant disorder in which hyperkeratosis is confined to the palms and soles.  The two major types can have a similar clinical appearance:
Diffuse epidermolytic palmoplantar keratoderma (also known as "Palmoplantar keratoderma cum degeneratione granulosa Vörner," "Vörners epidermolytic palmoplantar keratoderma", and "Vörner keratoderma") is one of the most common patterns of palmoplantar keratoderma, an autosomal dominant condition that presents within the first few months of life, characterized by a well-demarcated, symmetric thickening of palms and soles, often with a "dirty" snakeskin appearance due to underlying epidermolysis.: 506 
Diffuse nonepidermolytic palmoplantar keratoderma (also known as "Diffuse orthohyperkeratotic keratoderma," "Hereditary palmoplantar keratoderma," "Keratosis extremitatum progrediens," "Keratosis palmoplantaris diffusa circumscripta," "Tylosis," "Unna–Thost disease", and "Unna–Thost keratoderma") is inherited as an autosomal dominant condition and is present from infancy, characterized by a well-demarcated, symmetric, often "waxy" keratoderma involving the whole of the palms and soles.: 506–8 : 213

Focal
Focal palmoplantar keratoderma, a type of palmoplantar keratoderma in which large, compact masses of keratin develop at sites of recurrent friction, principally on the feet, although also on the palms and other sites, a pattern of calluses that may be discoid (nummular) or linear.

 Focal palmoplantar keratoderma with oral mucosal hyperkeratosis (also known as "Focal epidermolytic palmoplantar keratoderma," "Hereditary painful callosities," "Hereditary painful callosity syndrome," "Keratosis follicularis," "Keratosis palmoplantaris nummularis", and "Nummular epidermolytic palmoplantar keratoderma") is an autosomal dominant keratoderma that represents a clinical overlap syndrome with pachyonychia congenita type I but without the classic nail involvement.: 510

Punctate
Punctate palmoplantar keratoderma is a form of palmoplantar keratoderma in which many tiny "raindrop" keratoses involve the palmoplantar surface, skin lesions which may involve the whole of the palmoplantar surface, or may be more restricted in their distribution.: 505 
Type 1: Keratosis punctata palmaris et plantaris (also known as "Autosomal-dominant hereditary punctate keratoderma associated with malignancy," "Buschke–Fischer–Brauer disease," "Davis Colley disease," "Keratoderma disseminatum palmaris et plantaris," "Keratosis papulosa," "Keratoderma punctatum," "Keratodermia punctata," "Keratoma hereditarium dissipatum palmare et plantare," "Palmar and plantar seed dermatoses," "Palmar keratoses," "Papulotranslucent acrokeratoderma," "Punctate keratoderma," "Punctate keratoses of the palms and soles," and "Maculosa disseminata") is a skin condition, an autosomal dominant palmoplantar keratoderma with variable penetrance, characterized clinically by multiple, tiny, punctate keratoses over the entire palmoplantar surfaces, beginning over the lateral edge of the digits.: 509 : 212–213  It has been linked to 15q22-q24.
Type 2: Spiny keratoderma (also known as "Porokeratosis punctata palmaris et plantaris," "Punctate keratoderma," and "Punctate porokeratosis of the palms and soles") is an autosomal dominant keratoderma of late onset that develops in patients aged 12 to 50, characterized by multiple tiny keratotic plugs, resembling the spines on a music box, involving the entire palmoplantar surfaces.: 509 
Type 3: Focal acral hyperkeratosis (also known as "Acrokeratoelastoidosis lichenoides," and "Degenerative collagenous plaques of the hand") is a late-onset keratoderma, inherited as an autosomal dominant condition, characterized by oval or polygonal crateriform papules developing along the border of the hands, feet, and wrists.: 509  It is considered similar to Costa acrokeratoelastoidosis.

Ungrouped
Palmoplantar keratoderma and spastic paraplegia (also known as "Charcot–Marie–Tooth disease with palmoplantar keratoderma and nail dystrophy") is an autosomal dominant or x-linked dominant condition that begins in early childhood with thick focal keratoderma over the soles and, to a lesser extent, the palms.: 513 
Palmoplantar keratoderma of Sybert (also known as "Greither palmoplantar keratoderma," "Greither syndrome," "Keratosis extremitatum hereditaria progrediens," "Keratosis palmoplantaris transgrediens et progrediens" "Sybert keratoderma," and "Transgrediens and progrediens palmoplantar keratoderma") is an extremely rare autosomal dominant keratoderma (a skin condition involving horn-like growths) with symmetric severe involvement of the whole palmoplantar surface in a glove-and-stocking distribution.: 509  It was characterized by Aloys Greither in 1952