Anonychia-onychodystrophy with hypoplasia or absence of distal phalanges

Alternate names

Anonychia and absence/hypoplasia of distal phalanges; Cooks syndrome

Definition

Cooks syndrome is a malformation syndrome affecting the apical structures of digits and presenting with hypo/aplasia of nails and distal phalanges. More than half of digits are usually involved and the thumbs may appear digitalized.

Epidemiology

To date, less than 20 individuals have been described in the world literature.

Cause

The exact etiology of Cooks syndrome is still unknown but microduplications on chromosome 17q24.3 and involvement of a non-coding element of the SOX9 gene (17q24.3) have recently been associated in some patients with Cooks syndrome. The SOX9 gene is necessary for chondrocyte differentiation and cartilage formation.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

An autosomal dominant mode of inheritance has been proposed. Genetic counseling may be proposed and the recurrence risk is of 50%.

Signs and symptoms

Cooks syndrome is congenital and presents with hypo/anonychia, small or absent distal phalanges and digitalization of the thumbs. Usually, the nails of digits 1-3 are progressively deformed, with anonychia congenita totalis in the digits 4-5 and in all toes. Additional features include hypoplasia of the distal phalanges in digits 2-4 with absence of the distal phalanx of digit 5. In the feet, there is absence of all distal phalanges of digits 2-5 with hypoplasia of the distal phalanx of digit 1. Finger pads at the dorsal aspects of the affected fingers may occasionally be seen. To date, no facial dysmorphism has been associated with Cooks syndrome. Cooks syndrome is considered a clinical form of brachydactyly type B , distinct from the typical variant with sparing or duplication of the thumbs and caused by mutations in the ROR2 gene (9q22).

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Aplastic/hypoplastic toenail(Absent/small toenails)
• Brachydactyly(Short fingers or toes)
• Broad thumb(Broad thumbs)
• Dystrophic fingernails(Poor fingernail formation)
• Dystrophic toenail(Poor toenail formation)
• Split hand(Claw hand)
• Triphalangeal thumb(Finger-like thumb)

NIH genetic and rare disease info

• NIH info on Anonychia-onychodystrophy with hypoplasia or absence of distal phalanges

Anonychia-onychodystrophy with hypoplasia or absence of distal phalanges is a rare disease.

Anonychia-onychodystrophy with hypoplasia or absence of distal phalanges Resources
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