Multifactorial pathological hip subluxation in neurofibromatosis type-1 (NF1) due to intra-articular plexiform neurofibroma, lumbar radiculopathy and neurofibromatous polyneuropathy

Intra-articular hip neurofibromas in von Recklinghausen's disease

Neurofibromatosis is a genetic disorder with osteo-articular manifestations. The intra-articular location of neurofibroma is scarce.

Spontaneous Hip Dislocation Complicating the Management of Malignant Peripheral Nerve Sheath Tumor Arising Within a Plexiform Neurofibroma

Neurofibromatosis type 1 (NF1) is one of the most common inherited neurological disorders. It can cause plexiform neurofibromas, leading to diffuse enlargement of a nerve or nerves within the body. There are benign in general, however, can cause significant symptoms due to their size, including bony erosion, pain, and joint instability. Unfortunately, they also have the capacity to become malignant by internal transformation into a malignant peripheral nerve sheath tumor (MPNST). The case presented here is a 27-year-old male with NF1 that was followed for years with a pelvic girdle plexiform neurofibroma whose course was complicated by transformation to MPNST and a spontaneous hip dislocation. He underwent excision, Girdlestone procedure, chemotherapy, and radiation. Unfortunately, he subsequently developed lung metastases and is part of a clinical trial with an MDM2 inhibitor and pembrolizumab.

The concept of type 2 segmental mosaicism, expanding from dermatology to general medicine

In autosomal dominant skin disorders, the well-known type 1 segmental mosaicism reflects heterozygosity for a postzygotic new mutation. By contrast, type 2 segmental mosaicism originates in a heterozygous embryo from an early postzygotic mutational event giving rise to loss of the corresponding wild-type allele, which results in a pronounced segmental involvement being superimposed on the ordinary, non-segmental phenotype. Today, this concept has been proven by molecular analysis in many cutaneous traits. The purpose of this review was to seek publications of cases suggesting an extracutaneous manifestation of type 2 segmental mosaicism. Case reports documenting a pronounced extracutaneous segmental involvement were collected from the literature available in PubMed and from personal communications to the author. Pertinent cases are compared to the description of cutaneous segmental mosaicism of type 1 or type 2 as reported in a given trait. In total, reports suggesting extracutaneous type 2 segmental mosaicism were found in 14 different autosomal dominant skin disorders. In this way, clinical evidence is accumulated that extracutaneous type 2 segmental mosaicism does likewise occur in many autosomal dominant skin disorders. So far, however, molecular proof of this particular form of mosaicism is lacking. The present review may stimulate readers to inform colleagues of other specialties on this new concept, in order to initiate further research in this particular field of knowledge that has important implications for diagnosis, treatment and genetic counselling.