Superimposed Mosaicism in the Form of Extremely Extended Segmental Plexiform Neurofibroma Caused by a Novel Pathogenic Variant in the NF1 Gene.

Plexiform neurofibromas occurring in approximately 20-50% of all neurofibromatosis type-1 (NF1) cases are histologically benign tumors, but they can be fatal due to compression of vital structures or transformation to malignant sarcomas or malignant peripheral nerve sheath tumors. All sizeable plexiform neurofibromas are thought to result from an early second mutation giving rise to a loss of heterozygosity of the NF1 gene. In this unusual case, a 12-year-old girl presented with a rapidly growing, extremely extensive plexiform neurofibroma with segmental distribution over the entire right arm, extending to the right chest wall and mediastinum, superimposed on classic cutaneous lesions of NF1. After several surgical interventions, the patient was efficiently treated with an oral selective MEK inhibitor, selumetinib, which resulted in a rapid reduction of the tumor volume. Molecular analysis of the NF1 gene revealed a c.2326-2 A>G splice-site mutation in the clinically unaffected skin, peripheral blood sample, and plexiform neurofibroma, which explains the general clinical symptoms. Furthermore, a novel likely pathogenic variant, c.4933dupC (p.Leu1645Profs*7), has been identified exclusively in the girl's plexiform neurofibromas. This second-hit mutation can explain the extremely extensive segmental involvement.

The First Reported Case of Trichothiodystrophy in Hungary: A Young Male Patient with Mutations in the ERCC2 Gene.

Trichothiodystrophy, also called sulphur-deficient brittle hair syndrome, is a rare autosomal recessive genetic disorder of DNA repair and transcription. Trichothiodysthrophy is characterised by dry, thin, easily broken hair, showing alternating light and dark pattern called 'tiger tail' banding under polarizing light microscopy. According to our knowledge, our report is the first one on this rare disorder from Hungary: a case of a 9-year-old boy showing clinical features typical of trichotiodystrophy. Sequence analysis of the ERCC2 gene identified two recurrent trichothidodystrophy missense heterozygous mutations - c.934G/A p.Asp312Asn (CM015299) and c.2251A/C p.Lys751Gln (CM004814) - suggesting compound heterozygous state of the patient and confirming the clinically suspected diagnosis of trichothiodystrophy.