Hypophosphatemic rickets: A rare complication of congenital melanocytic nevus syndrome

Burosumab treatment in a child with cutaneous skeletal hypophosphatemia syndrome: A case report

Cutaneous skeletal hypophosphatemia syndrome (CSHS) is a rare disorder caused by somatic mosaicism for the gain of function RAS mutations . Affected patients have segmental epidermal nevi, dysplastic cortical bony lesions, and fibroblast growth factor-23 (FGF23)–mediated hypophosphatemic rickets. Herein, we describe a case of an Emirati girl with CSHS, whose hypophosphatemic rickets and osteomalcic pseudofractures and dysplastic bony lesions failed to recover due to poor adherence to treatment with oral phosphate supplements and alfacalcidol (conventional treatment). Treatment with burosumab, a fully human immunoglobulin G1 monoclonal antibody against FGF23 for 12 months, led to normalization of serum inorganic phosphate and alkaline phosphatase levels, radiographic healing of rickets, partial healing of pseudofractures, improvement in 6-minute walk test, and the physical scale of the Pediatric Quality of Life Inventory. We conclude that burosumab is effective in treatment of CSHS, however results of the ongoing phase 2 trial in adults (NCT02304367) are awaited.

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Cutaneous skeletal hypophosphatemia syndrome (CSHS) is caused by somatic gain-of-function RAS mutations.

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It is associated with fibroblast growth factor-23 (FGF23) mediated hypophosphatemic rickets.

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Burosumab, a monoclonal antibody to FGF23 may have a role in the treatment of CSHS.

An update on congenital melanocytic nevus syndrome: A case report and literature review

Congenital melanocytic nevus syndrome (CMNS) is a rare condition characterized by pigmented skin lesions that are usually present at birth and are associated with an increased risk of neurological abnormalities and malignant melanoma. It mostly results from a post-zygotic NRAS mutation of neural-derived crest cells, leading to uncontrolled cell growth. Because of the increased knowledge of the genetics underlying CMNS, targeted therapy becomes a promising treatment option. We present a case of CMNS in a newborn. Physical examination at birth showed a giant congenital melanocytic nevus, extending from the occipital to the lower lumbar region. A magnetic resonance imaging scan revealed multiple cerebral and cerebellar parenchymal lesions. Genetic analysis of the cutaneous lesions showed the presence of an NRAS Q61R mutation. The patient was treated with dermabrasion to reduce the color intensity of the nevus. However, this was complicated by recurrent wound infections and laborious wound healing. At the age of 1 year, the patient had an age-appropriate psychomotor development, without neurological deficits.

Congenital melanocytic nevi

PURPOSE OF REVIEW

To update pediatric providers on new developments in our understanding of the clinical presentation, genetics, and systemic risks associated with congenital melanocytic nevi (CMN).

RECENT FINDINGS

CMN are primarily caused by sporadic postzygotic somatic mutations, most frequently in NRAS, and studies of the genetic underpinnings of CMN have demonstrated a diverse array of genetic drivers. The primary complications of large and giant CMN include neurocutaneous melanocytosis and malignant melanoma. Abnormalities in CNS MRI may predict a worse clinical course for patients and increased risk of melanoma. Targeted therapies of the MEK pathway have begun to be studied for the treatment of CMN and prevention of associated complications.

SUMMARY

Patients with large and giant CMN should be managed by an interdisciplinary care team for the monitoring of dermatologic, neurologic, and psychosocial concerns. Ongoing research is underway to better characterize the genetic drivers of CMN and to better guide development of targeted therapeutics.