Pachyonychia Congenitia Project

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AAGAB

Commonly referred to as “Type 1 Punctate Palmar Plantar Keratoderma”

Facts

  • What does AAGAB stand for? alpha and gamma adaptin binding protein 341
  • What does the AAGAB gene do? participates in protein sorting & endocytosis1
  • What happens when AAGAB becomes mutated? dysfunctional endocytic recycling of EGFR proteins1
  • Clinical significance of mutation? cellular hyperproliferation & hyperkeratotic lesions1

About Type 1 Punctate Palmar Plantar Keratoderma

Skin disease caused by AAGAB mutations is known as Buschke-Fischer-Brauer’s Disease or Type 1 Punctate Palmar Plantar Keratoderma (PPPK1). However, not all cases of PPPK1 are caused by AAGAB mutations.2 The disease is very rare and is estimated to have a prevalence of 1.17 per 100,000.1 PPPK1 is passed down from a parent to their offspring in an autosomal dominant inheritance pattern.2 This means that it only takes one copy of the mutated AAGAB gene from one parent to cause PPPK1. The parent who has PPPK1 has a 50% chance of passing the mutated AAGAB gene in each pregnancy. Genetic testing is necessary to determine whether or not an individual with symptoms of PPPK1 are caused by a mutation in the AAGAB gene.1

Symptoms of PPPK1

Signs of PPPK1 appear in late childhood to adulthood.2 Several small hyperkeratotic lesions start to appear on the palms of the hands as well as the soles of the feet. Hyperkeratotic lesions are defined papules that appear as thickening of the outer layer of skin.2 The lesions typically have an irregular distribution on the palms and soles, with more lesions present on areas of the skin that are subject to higher pressure. As a person with PPPK1 grows older, they are likely to experience a greater number of lesions. This is thought to be due to mechanical or environmental stressors rather than the actual aging process.2 There is rarely any sign of nail changes in people who have PPPK1, although it can and does occur in some cases.3

IPCRR Data for AAGAB

Plantar Keratoderma75%
Always (never goes away)75%
Sometimes (clears up at times)0%
Seldom (feet usually clear)0%
Plantar Keratoderma – Onset
Birth or less than 1 year0%
1 to 4 years old17%
5 to 14 years old50%
15 years and over33%
Plantar Pain75%
Often require medications for pain0%
Very painful, but do not use medications38%
Somewhat painful25%
Palmar Keratoderma75%
Always (never goes away)75%
Sometimes (clears up at times)0%
Seldom (hands usually clear)0%
Toenail Dystrophy38%
all 10 toenails thickened13%
7-9 toenails thickened0%
4-6 toenails thickened13%
1-3 toenails thickened13%
Toenails – Onset
Birth or less than 1 year0%
1 to 4 years old33%
5 to 14 years old0%
15 years and over33%
Fingernail Dystrophy13%
all 10 toenails thickened13%
7-9 toenails thickened0%
4-6 toenails thickened0%
1-3 toenails thickened0%
Fingernails – Onset
Birth or less than 1 year0%
1 to 4 years old100%
5 to 14 years old0%
15 years and over0%
Oral Leukokeratosis0%
Cysts0%
Follicular Hyperkeratosis0%
Natal or Prenatal Teeth0%

Data from 2022 Sample Size N=8

References

  1. Gómez-García AC, Salas-Alanís JC, Bar-Fernandez N, Mendoza-Meza R, Díaz-Montes SM, Fajardo-Ramírez OR. A novel AAGAB mutation in a Peruvian family with punctate palmoplantar keratoderma. Acta Dermatovenerol Alp Pannonica Adriat. 2021;30(1):47-48.
  2. Elhaji Y, Hedlin C, Nath A, et al. AAGAB Mutations in 18 Canadian Families With Punctate Palmoplantar Keratoderma and a Possible Link to Cancer. J Cutan Med Surg. 2020;24(1):28-32. doi:10.1177/1203475419878161
  3. Furniss M, Higgins CA, Martinez-Mir A, et al. Identification of distinct mutations in AAGAB in families with type 1 punctate palmoplantar keratoderma. J Invest Dermatol. 2014;134(6):1749-1752. doi:10.1038/jid.2014.

Above photos are from individuals in the IPCRR with confirmed AAGAB mutations.