A tyrosine kinase-activating variant Asn666Ser in PDGFRB causes a progeria-like condition in the severe end of Penttinen syndrome.

Missense variants located to the "molecular brake" in the tyrosine kinase hinge region of platelet-derived growth factor receptor-ß, encoded by PFGFRB, can cause Penttinen-type (Val665Ala) and Penttinen-like (Asn666His) premature ageing syndromes, as well as infantile myofibromatosis (Asn666Lys and Pro660Thr). We have found the same de novo PDGFRB c.1997A>G p.(Asn666Ser) variants in two patients with lipodystrophy, acro-osteolysis and severely reduced vision due to corneal neovascularisation, reminiscent of a severe form of Penttinen syndrome with more pronounced connective tissue destruction. In line with this phenotype, patient skin fibroblasts were prone to apoptosis. Both in patient fibroblasts and stably transduced HeLa and HEK293 cells, autophosphorylation of PDGFRß was observed, as well as increased phosphorylation of downstream signalling proteins such as STAT1, PLCγ1, PTPN11/SHP2-Tyr580 and AKT. Phosphorylation of MAPK3 (ERK1) and PTPN11/SHP2-Tyr542 appeared unaffected. This suggests that this missense change not only weakens tyrosine kinase autoinhibition, but also influences substrate binding, as both PTPN11 tyrosines (Tyr542 and Tyr580) usually are phosphorylated upon PDGFR activation. Imatinib was a strong inhibitor of phosphorylation of all these targets, suggesting an option for precision medicine based treatment.

Expansion of the phenotype of Kosaki overgrowth syndrome.

Skeletal overgrowth is a characteristic of several genetic disorders that are linked to specific molecular signaling cascades. Recently, we established a novel overgrowth syndrome (Kosaki overgrowth syndrome, OMIM #616592) arising from a de novo mutation in PDGFRB, that is, c.1751C>G p.(Pro584Arg). Subsequently, other investigators provided in vitro molecular evidence that this specific mutation in the juxtamembrane domain of PDGFRB causes an overgrowth phenotype and is the first gain-of-function point mutation of PDGFRB to be reported in humans. Here, we report the identification of a mutation in PDGFRB, c.1696T>C p.(Trp566Arg), in two unrelated patients with skeletal overgrowth, further confirming the existence of PDGFRB-related overgrowth syndrome arising from mutations in the juxtamembrane domain of PDGFRB. A review of all four of these patients with an overgrowth phenotype and PDGFRB mutations revealed postnatal skeletal overgrowth, premature aging, cognitive impairment, neurodegeneration, and a prominent connective tissue component to this complex phenotype. From a functional standpoint, hypermorphic mutations in PDGFRB lead to Kosaki overgrowth syndrome, infantile myofibromatosis (OMIM #228550), and Penttinen syndrome (OMIM #601812), whereas hypomorphic mutations lead to idiopathic basal ganglia calcification (OMIM #615007). In conclusion, a specific class of mutations in PDGFRB causes a clinically recognizable syndromic form of skeletal overgrowth.

Infantile myofibromatosis: a nontraumatic cause of neonatal brachial plexus palsy.

Most injuries to the neonatal brachial plexus occur acutely at birth, and are iatrogenic in origin. However, when weakness is accompanied by atrophy, nontraumatic etiologies should be considered. The differential diagnosis of chronic congenital brachial plexopathy includes cervical bone malformations, humeral osteomyelitis, varicella, and compression from various types of infantile tumors. An illustrative male infant delivered at 37 weeks of gestation with wasted musculature of the left upper arm, ipsilateral Horner's syndrome, and a hemidiaphragm is presented. On further examination, this patient manifested an underlying cervical tumor compressing the brachial plexus. Diagnostic steps leading to the pathologic identification of a solitary cervical myofibroma included physical examination, electromyography, radiographic imaging, and open biopsy. This report emphasizes the importance of differentiating acute from chronic congenital plexus palsy and of recognizing the possibility that infection or neoplasm may underlie the latter.

Infantile myofibroma: a case report and review of the literature.

This article presents a case report of a 37-week gestational age (GA) female infant (CK) whose first ultrasound at 35 weeks' GA revealed polyhydramnios, fetal ascites, and a possible diaphragmatic hernia. At birth, CK had a grossly distended abdomen, prominent abdominal veins, hepatomegaly, bounding femoral pulses, and generalized edema. Initial imaging identified an absent ductus venosus, absent segment of the inferior vena cava (IVC), and prominent superior vena cava to the right atrium. A computed tomography (CT) scan showed a mass contiguous with the liver causing compression of the IVC. Biopsy confirmed infantile myofibromatosis (IM), an uncommon soft tissue neoplasm that may present at birth or in early infancy. Although rare, this neoplasm is the most common fibrous tumor of infancy. The case of CK was unusual because the solitary IM lesion was in an atypical location; a solitary lesion is not commonly found in the viscera, and solitary lesions are predominant in males. Although lesions are often benign, visceral involvement is associated with high mortality. The cause is unknown, although familial cases have been reported. This article describes the key features of IM, possible treatment options, nursing care, and prognosis for infants with the disease.

Solitary infantile myofibromatosis in the lateral orbit floor showing spontaneous regression.

Infantile myofibromatosis is a rare benign tumour usually occurring early in infancy. We describe the case of a 10-year-old boy with solitary infantile myofibromatosis in the left lateral orbit floor which regressed spontaneously. Although our patient was older than previously reported cases and showed bony destruction confirmed by computed tomography (CT), this tumour was diagnosed as infantile myofibromatosis based on immunohistochemical findings. The tumour disappeared spontaneously six months after incisional biopsy, that also indicated this tumour was an infantile myofibromatosis.

[Cerebral control over locomotor function in occupational hand disease caused by local muscular overstrain]. / Tserebral'noe obespechenie dvigatel'noi funktsii pri professional'nykh zabolevaniiakh ruk ot regional'nogo myshechnogo peretruzhivaniia.

Predominant orientation of local muscular load to proximal or distal portions of shoulders and upper limbs considerably influences features of changes in brain functions and blood supply. Characteristic for plasterers, localization of myogeloses in upper part of trapezium muscles causes not only impaired vertebrobasillar circulation, but also venous cerebral stasis and caudal medullar dysfunction. Clinical symptoms are vestibular disorders, depressed functions of hearing, chronic venous cerebral congestion, posture-tonic disorders. Local loads on distal portions of limbs have other mechanisms of cerebral and peripheral disorders.

Solitary infantile myofibromatosis in the femur.

We report on a case of the solitary type of infantile myofibromatosis of the right femur in an 11-month female. Radiographically, a well-defined osteolytic lesion was seen in the diaphysis of the right femur. Pathological study revealed that the spindle-shaped cells with eosinophilic cytoplasm were arranged in a fascicular and intertwining fashion. The cleft-shaped vascular spaces were observed between tumor nodules. Immunohistochemical staining caused many tumor cells to react for vimentin, alpha-smooth muscle actin and desmin. Ultrastructural study revealed numerous thin and intermediate types of filaments in the cytoplasm of the cells. To our best knowledge, this is the third reported case of solitary infantile myofibromatosis of long bones.

del(6)(q12q15) as the sole cytogenetic anomaly in a case of solitary infantile myofibromatosis.

We describe a case of light microscopically typical solitary, infantile myofibromatosis in a 6-month old boy. The myofibroblastic differentiation of the tumor was supported by immunohistochemical and ultrastructural analyses. Cytogenetic and FISH analyses revealed a pseudodiploid karyotype with an interstitial deletion of the long arm of one chromosome 6, del(6)(q12q15), as the sole anomaly. The results demonstrate the usefulness of cytogenetics and FISH in distinguishing this type of lesion from infantile fibrosarcoma. To the best of our knowledge this is the first cytogenetic analysis of solitary infantile myofibromatosis.

Massive apoptosis in infantile myofibromatosis. A putative mechanism of tumor regression.

Two cases of solitary infantile myofibromatosis (IM) are presented. Solitary IM are tumors prone to spontaneous regression. Histopathologically, several tumor lobules in our IM cases had central areas of massive cell death, with nuclear pyknosis, cytoplasmic hyalinization and nuclear fragmentation but without lymphoid or neutrophilic cell infiltration. These central cell death areas consisted of about 40% in case 2 and 50% in case 1 of the entire tumor tissues, respectively. Electron microscopy revealed that the condensed nuclei and cytoplasm were fragmented into "apoptotic bodies", with or without phagocytosis by histiocytes. DNA fragmentation, as evidenced by the terminal deoxy transferase-mediated uptake of biotinylated dUTP, was identified at massive cell death areas on paraffin sections from both cases. A characteristic 180- to 190-bp nucleosomal ladder was detected in DNA obtained from the tumor cells in case 1. The collective evidence suggested that these tumors underwent a central, massive apoptosis. As massive cell death similar to that seen in the present cases has been described in other documented cases of IM, we propose that the spontaneous regression that frequently occurs with this type of tumor may be mediated by massive apoptotic cell death.