Hypomelanosis of Ito (incontinentia pigmenti achromians)

Definition

Hypomelanosis of Ito (formerly incontinentia pigmenti achromians) is a rare pigmentary disorder with streaky and whorled hypopigmented macules along Blaschko lines, often associated with changes in other organ systems, particularly the nervous system. Today it is understood as a non-specific cutaneous sign of genetic mosaicism rather than a single syndrome. It was described in 1952 by the Japanese dermatologist Minoru Ito.

Aetiopathogenesis

The basis is chromosomal or genetic mosaicism arising after conception; as a rule, the disorder is therefore not inherited. Blaschko lines mark the boundaries between the two cell lines in embryonic skin.

Clinical features

• Initially small (0.5–1 cm) pale to white macules that merge into larger areas; whorled on the trunk, linear on the arms and legs.
• Usually more than two dermatomes and both sides of the body are involved, but asymmetrically; the palms, soles and scalp are usually spared.
• Associated abnormalities in about 30–50% (some studies report neurological abnormalities in up to 75–94%): seizures, developmental delay and intellectual disability, abnormal muscle tone, hemimegalencephaly; also the eyes, teeth, skeleton, heart and kidneys. In a paediatric neurology series of 76 children, 57% had intellectual disability.

Diagnosis

• Clinical: the changes are present from birth and are usually recognised in the first two years of life.
• Thorough history and physical, neurological and ophthalmological examination to detect associated abnormalities, together with assessment of growth, development, teeth and renal function.
• In early stages, distinction from incontinentia pigmenti, whose skin lesions can look similar.

Differential diagnoses

• Naevus depigmentosus (achromic naevus)
• Oculocutaneous albinism
• Vitiligo
• Piebaldism
• Incontinentia pigmenti
• Pityriasis versicolor (tinea versicolor)

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References (selection)

1. DermNet: Hypomelanosis of Ito
2. DermNet: Cutaneous mosaicism
3. PubMed: Hypomelanosis of Ito (PMID 26564088)
4. PubMed: Neurocutaneous disorders identified in the neonatal period and infancy: Hypomelanosis of Ito (PMID 39389656)
5. PubMed: Hypomelanosis of Ito: no entity, but a cutaneous sign of mosaicism (PMID 10398257)
6. PubMed: Hypomelanosis of ITO. A study of 76 infantile cases (PMID 9533559)

Cross-references