Cutaneous Mosaicism Service

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What are Mosaic disorders?

Mosaic disorders are a group of rare disorders which are collectively not so rare. They are defined as a group by a common disease mechanism – they are caused by a genetic mutation (a change) in a single cell in the developing baby during pregnancy. This leads to the baby being born with a mixture of normal cells (not carrying the mutation) and disease cells (carrying the mutation). It is this mixture which is referred to as mosaicism. This event can happen to any child, and importantly is not inherited from either parent.

The effects of the mutation depend on lots of different things. The most important ones are when it occurs and whereabouts it occurs in the body. In general, the earlier the mutation happens, the more serious the disease will be. As a result of the variability, each child with a mosaic disorder is unique in their disease and needs to be assessed uniquely.

Mosaic disorders affecting the skin are currently the best known because it is possible to see the effects on the skin as birthmarks. As a result, although they often affect many body systems as well as the skin, mosaic disorders affecting the skin are looked after by Paediatric Dermatologists and Dermatologists.

About the NHS England Rare Disease Collaborative Network for Mosaic Disorders (RDCN-MD)

The NHS England Rare Disease Collaborative Network for Mosaic Disorders (RDCN-MD) is led by GOSH Paediatric Dermatology and has an adult centre at St Thomas’ hospital, London. Other than the two specialist centres we have established a national network of named consultant contacts.

This Rare disease collaborative network will focus on the severe end of the spectrum of these diseases.

If you are interested in becoming part of the RDCN-MD as a named consultant contact for the joint care of patients with mosaic disorders please send an email to: with the subject heading “Local Consultant Contact Request”. The idea of the local consultant contact network is to foster national expertise to improve patient care, and to improve coordination and communication between local and specialist centres. Although this is an NHS England badge we are very keen to include local contacts from the other union countries as the specialist centres will continue to see patients from all over the UK.

The duties of named consultant contacts would be to undertake follow up appointments, to arrange for any local monitoring, and to check and communicate local results to the broader care team. Named consultant contacts will be invited to attend a free annual clinical teaching/update day. This will be held in London in person to try to foster a real network of clinicians who meet yearly and exchange knowledge, but will also have virtual access. It will also be possible for named contacts to attend the RDCN-Mosaic Disorders MDTs, which will occur three-monthly in London and virtually. This forum will be for learning but also for discussing cases.

Learn more about Rare Disease Collaborative Networks on the NHS England webpage.

Named local consultant contacts

  • Susannah Hoey (Dermatology) - Royal Victoria Hospital, Belfast, Northern Ireland
  • Lindsay Shaw (Dermatology) - Bristol Children’s Hospital and Bristol Royal Infirmary, Bristol, England
  • Saleem Taibjee (Dermatology) -Dorset County Hospital, Dorset, England
  • Julia Gass (Dermatology) - Addenbrooke’s Hospital, Cambridge
  • Natasha Stembridge (Dermatology) - Addenbrooke’s hospital, Cambridge
  • Ravinder Atkar (Dermatology) - Royal London Hospital and Whipps Cross Hospital , London
  • Marie-Louise Lovgren (Dermatology) - Birmingham Children's Hospital
  • James Halpern (Dermatology) - Walsall Healthcare NHS Trust, Walsall, England
  • Seema Garg (Dermatology) - Rotherham Hospital, Rotherham
  • Raakhee Ramesh (Dermatology) - Sandwell and West Birmingham Hospitals
  • Rachel Hart (Oncology) - Liverpool Women's Hospital
  • Alexis Cuell (Dermatology) - Walsall Healthcare NHS Trust, Walsall, England
  • Catherine Harwood (Dermatology) - Barts Health NHS Trust, London
  • Nagendra Venkata (Paediatrics) - Royal Devon University Healthcare NHS Foundation Trust
  • Nick Wilson-Jones (Plastic Surgery) - Welsh Centre for Burns and Plastic Surgery
  • Nigel Burrows (Dermatology) - Cambridge University Hospitals NHS Foundation Trust
  • Paul Arundel (Paediatric Bone Disease) Sheffield Children's Hospital
  • Sarah Wedderburn (Genetics) Queen Elizabeth University Hospital, Glasgow
  • Paula Beattie (Dermatology) Royal Hospital for Children, Glasgow
  • Anna Dubois (Dermatology) Royal Victoria Infirmary, Newcastle

Aims of the RDCN-Mosaic Disorders

The overarching aims of the RDCN-MDs are in line with those for all RDCNs:

  • to increase knowledge and understanding of mosaic disorders
  • to progress research
  • to improve patient experience

The specific aims of the RDCN-MDs are:

  • to reduce mean time to first seeing a specialist
  • to reduce the number of trips to the specialist centre
  • to improve access to accurate clinical and genetic diagnosis
  • to improve transition from paediatric to adult services, and to provide new adult access to specialist opinion
  • to improve coordination of care between the RDCN and local hospitals

Conditions which can be referred to the mosaicism service

Congenital naevi of all types, including:

  • melanocytic – small single lesions excluded
  • epidermal – small single round sebaceous naevi excluded
  • adnexal - any
  • connective tissue – any

Vascular malformations of all types, including:

  • Arteriovenous – any
  • Venous – small single asymptomatic lesions excluded
  • Capillary – small single lesions excluded
  • Lymphatic – any
  • Mixed – any

Suspected mosaic disorders of unknown diagnosis

  • These would often be indicated by asymmetry of growth (overgrowth or undergrowth or body parts), extensive or multiple birthmarks (same type or multiple types), neurocutaneous disorders which don’t fit with known germline diagnoses

Mosaic versions of germline diseases

  • For example mosaic neurofibromatosis type 1, mosaic CM-AVM syndrome, mosaic tuberous sclerosis, mosaic Darier disease, mosaic Gorlin syndrome

Specific exclusions

  • Infantile haemangioma
  • X-linked germline disorders which present with Blaschkolinear patterning such as incontinenti pigmenti, Goltz disease

Referral criteria to RDCN-MDs

Mandatory primary RDCN-MDs referral criterion

Every patient referred into the RDCN service must have a clinician in charge of coordinating their care in their local hospital. This is to optimise coordination of patient care and communication between the RDCN and the local team, and to reduce the requirement for patient travel. This clinician must either be the referring clinician or be named in the referral letter if coming from a GP.

Referral to the local clinician at the time of GP referral and naming of that clinician in the referral letter is sufficient at that stage, so that referral is not delayed by waiting for local appointments. This named clinician will be expected to remain involved in patient care throughout their care under the RDCN.

For children the named clinician would be expected to be in Dermatology or Paediatrics, and for adults in Dermatology. However, for patients requiring systemic targeted therapies for their mosaic disorders (for example Sirolimus, Trametinib, Miransertib, Dabrafenib) an oncology professional may be the most appropriate even though these drugs are being used for mosaic disorders and not malignancy.

GPs can refer via E-RS to the Dermatology (Paediatrics)- Referral Assessment Service at Great Ormond Street Hospital, naming the local clinician in the referral letter. Details on how to refer via E-RS can be found on our website.

Secondary RDCN-MDs referral criteria

  1. Suspected MD but no clinical diagnosis.
  2. Known MD but no genetic diagnosis.
  3. Suspected or known MD with clinical problems requiring management plan.

Research into mosaic disorders

Where the genes are not already known for particular diagnoses, or where there is no diagnosis, or if the known genes transpire to be normal, we offer patients further investigation on a research basis.