Intraosseous calvarial haematoma mimicking a skull tumour in a child with Noonan syndrome: a case report

Abstract

Introduction

Noonan syndrome is an autosomal dominant disorder caused by mutations in genes within the RAS–mitogen-activated protein kinase (RAS/MAPK) signalling pathway, a key intracellular signalling cascade involved in cell growth, differentiation, and survival [1]. It is characterized by multisystem involvement, including dysmorphic facial features, congenital heart disease, musculoskeletal abnormalities, and growth retardation [2]. Importantly, individuals with Noonan syndrome demonstrate an increased predisposition to certain malignancies, particularly giant cell tumours of bone, which must be considered when evaluating osseous lesions.

Bleeding diathesis is reported in ~20%–30% of patients with Noonan syndrome and is commonly attributed to coagulation factor deficiencies (most frequently Factor XI), platelet dysfunction, or a combination of both [3, 4]. Notably, clinically significant bleeding may occur despite normal routine coagulation studies [3].

Although calvarial lesions in this population are rare and most often represent giant cell tumours [5], non-neoplastic entities may present with similar clinical and radiological features. Intraosseous calvarial haematoma has not yet been reported in association with Noonan syndrome. Here, we present a case of intraosseous calvarial haematoma in a paediatric patient with Noonan syndrome and discuss its diagnostic and management implications.

Case report

A 14-year-old female with genetically confirmed Noonan syndrome (diagnosed at age two) presented with progressively enlarging masses over the right frontoparietal calvarium over a 2-month period. The patient reported a persistent right-sided headache, exacerbated in the supine position, associated with visual disturbance and intermittent tinnitus. There was no history of nausea, vomiting, diplopia, or seizures. A minor head injury from a fall was reported 1 week prior to presentation, notably after the initial appearance of the lesions. There was no history suggestive of a bleeding diathesis.

On examination, multiple firm, mildly tender, and fixed lesions were palpable over the right frontal and parietotemporal regions without overlying skin changes. Neurological examination was unremarkable, with no focal motor or sensory deficits and intact cranial nerves.

Non-contrast computed tomography of the head demonstrated multiple expansile osteolytic lesions involving the right frontal and parietal bones, with associated mass effect on the adjacent cerebral parenchyma. Magnetic resonance imaging with contrast revealed heterogeneous calvarial lesions with incomplete peripheral enhancement and no parenchymal invasion (Fig. 1). In the context of Noonan syndrome, a primary osseous neoplasm, particularly giant cell tumour, was considered the leading diagnosis.

Figure 1

Preoperative neuroimaging of the right frontoparietal calvarial lesion; (A and B) axial T2-weighted magnetic resonance images demonstrating a heterogeneous expansile right frontoparietal calvarial lesion with local mass effect on the adjacent cerebral hemisphere and no definite parenchymal invasion; (C) sagittal non-contrast T1-weighted magnetic resonance image showing outward and inward expansion of the calvarial lesion; (D) sagittal contrast-enhanced T1-weighted magnetic resonance image showing incomplete peripheral enhancement of the lesion; (E) susceptibility-weighted image demonstrating blooming artefact consistent with haemorrhagic products; (F) axial computed tomography (CT) image (brain window) demonstrating local mass effect related to the right calvarial lesion; (G and H) axial CT images (bone window) showing expansile osteolytic involvement of the right frontal and parietal bones with cortical thinning and skull expansion.

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Following multidisciplinary discussion, informed consent was obtained. Preoperative evaluation included cardiovascular and paediatric assessments, with echocardiography performed given the multisystem nature of the condition. Laboratory investigations, including complete blood count and coagulation profile, were within normal limits. However, due to the known association of Noonan syndrome with bleeding diathesis, blood products were prepared in advance.

The patient underwent craniectomy via a reverse question-mark incision. After elevation of the scalp flap, burr holes were placed and the affected bone segments were excised with macroscopic margins using a craniotome. Significant intraoperative haemorrhage occurred during bone margin management, with an estimated blood loss of ~1000 ml, requiring transfusion of three units of packed red blood cells and two units of fresh frozen plasma. Following haemostasis, the wound was closed in layers without immediate reconstruction.

Histopathological analysis demonstrated intraosseous collections composed of fibrin, extravasated erythrocytes, haemosiderin deposition, and granulation tissue within a reactive fibrous stroma, with no evidence of malignancy, consistent with chronic intraosseous haemorrhage (Fig. 2). Gross examination confirmed organized intraosseous blood clot formation within the expanded diploic space (Fig. 3).

Figure 2

Histopathological architecture of the calvarial lesion; photomicrograph (H&E stain) illustrating the diagnostic components of the intraosseous lesion (A) bone: surrounding calvarial trabeculae exhibiting reactive changes; (B) fibrous tissue: dense stroma indicative of a chronic reactive process; (C) granulation tissue: proliferation of fibroblasts and capillaries, characteristic of an organizing haemorrhage; (D) fibrinous material and RBCs: core of the haematoma composed of fibrinous debris and extravasated erythrocytes.

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Figure 3

Gross pathology formalin-fixed specimen showing intraosseous blood clot formation.

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The postoperative course was uneventful, with no new neurological deficits. Three weeks later, the patient underwent successful cranioplasty using a custom-designed polyetheretherketone (PEEK) implant.

Discussion

Osseous lesions in Noonan syndrome

This case presents a significant diagnostic challenge. The clinical history of progressively enlarging calvarial lesions, combined with radiographic evidence of expansile osteolytic masses, was highly suggestive of a primary bone tumour. In the context of Noonan syndrome, the differential diagnosis is strongly weighted towards giant cell tumours of bone, which are well documented in this population [5, 6]. Although the patient reported minor head trauma, its trivial nature and the progressive course of the lesions made a haemorrhagic aetiology less likely at initial evaluation.

Perioperative considerations and bleeding risk

A central consideration in this case is the clinical reasoning required when evaluating presumed neoplastic lesions in patients with Noonan syndrome. The established association with giant cell tumours increases suspicion for malignancy and may prompt early surgical intervention. However, this case highlights an equally important factor: the high prevalence of bleeding diathesis in this population. As demonstrated, significant intraoperative haemorrhage may occur despite unremarkable routine coagulation studies, likely reflecting occult platelet dysfunction or unrecognized factor deficiencies [3].

Diagnosis

The histopathological diagnosis of intraosseous haematoma fundamentally altered the interpretation of this case. A lesion initially suspected to represent an aggressive neoplasm was ultimately found to be a benign process that closely mimicked malignancy on imaging [7]. This underscores the importance of histopathological confirmation prior to definitive diagnosis, particularly when clinical and radiological findings are inconclusive.

Management

The surgical strategy also warrants consideration. The decision to defer immediate reconstruction was necessitated by intraoperative blood loss and ensured patient safety. Delayed cranioplasty enabled reconstruction using a custom 3D-printed polyetheretherketone (PEEK) implant, which offers advantages in contouring accuracy and biocompatibility compared with traditional materials, particularly in paediatric patients with complex cranial defects [8–10].

To the best of our knowledge, this is the first reported case of intraosseous calvarial haematoma in a patient with Noonan syndrome.

Conclusion

We report a rare case of chronic intraosseous calvarial haematoma in a paediatric patient with Noonan syndrome. This case highlights the importance of considering non-neoplastic entities in the differential diagnosis of calvarial lesions, as they may clinically and radiologically mimic aggressive bone tumours. It also underscores the risk of significant intraoperative haemorrhage despite normal coagulation studies, emphasizing the need for careful perioperative planning. Custom 3D-printed PEEK implants provide an effective option for reconstruction in such complex cases.

Conflicts of interest

The authors declare no conflicts of interest.

Funding

This research received no external funding.

Ethical approval

Ethical approval was not required for this case report in accordance with institutional policy.

Consent

Written informed consent was obtained from the patient’s legal guardian for publication of this case report and accompanying images.

Guarantor

Bilal Ibrahim accepts full responsibility for the work and the conduct of the study.

References