Pectus carinatum in a patient with neurofibromatosis

Clinical History

A 48-year-old male patient with history of neurofibromatosis 1 was referred to the radiology department for a follow-up Computed Tomography of his chest in order to evaluate multiple cutaneous neurofibromas and exclude the presence of intrathoracic or spinal disease.

Imaging Findings

The CT examination of this patient revealed the presence of numerous widespread cutaneous nodules, which could be attributed to neurofibromas caused by the underlying disease. (Fig. 1) The most conspicuous cutaneous neurofibroma measured 16x4 cm in an axial plane and was situated in the left anterior chest wall. (Fig. 1) There were no paraspinal masses or widened intervertebral foramen. Regarding the lung parenchyma, extensive emphysema was present. (Fig. 2)
Of note was the fact that the patient’s chest was rhomboid in shape with the sternum projecting anteriorly. This configuration of the chest wall was characteristically identified on axial cross-sectional CT images. The anteroposterior diameter of the chest was 173 mm, whereas the transverse one was 279 mm. As a result, the pectus index was 1.61. (Fig. 2) Multiplanar Reconstruction (MPR) and Volume Rendering Technique (VRT) images were created to better illustrated the chest wall anatomy. (Fig. 2)

Discussion

The congenital presence of anteriorly displaced sternum and adjacent costal cartilages is characterized as pectus carinatum (PC), also known as pigeon breast. [1, 2] It represents the second most common sternal congenital anomaly after pectus excavatum, with a reported prevalence of 0.675%. PC may be hereditary, affects men four times more than women and coexists with scoliosis in more than 30% of cases. Association with congenital heart disease has been described only in a minority of cases. [1, 3] PC is also reportedly associated with genetic conditions like Marfan and Noonan syndromes and rarely coexists with neurofibromatosis. [2, 4] Two main types of PC have been described, each with different surgical implications. Currarino-Silverman syndrome refers to the presence of a chondromanubrial deformity with protrusion of the manubrium and upper sternum. Chondrogladiolar deformity describes the protrusion of the middle and lower sternum (keel chest). [1-3] This type involves 95% of cases. [2] According to the literature, a third type of PC includes lateral PC with unilateral protrusion of costal cartilages and sternal rotation. [3] PC can finally be iatrogenic and represent a complication of surgery for pectus excavatum. [2]
Lateral chest radiographs can successfully identify PC with increased anteroposterior diameter of the chest caused by anterior protrusion of the sternum. [1] Even if some authors consider lateral radiographs enough for preoperative work-up, CT and MRI can further evaluate sternal anatomy and provide accurate measurements. [2] The pectus index has been introduced to diagnose both pectus excavatum and pectus carinatum and assess the need for surgical correction by objectively grading the sternal malformation. This index is calculated by dividing the transverse diameter of the chest by its anteroposterior one. These diameters can be obtained by either CT or MRI. Normal values of the pectus index are 2.21 to 2.91 (mean: 2.56, standard deviation: ±0.35). A pectus index greater than these values is indicative of pectus excavatum, whereas an index value between 1.42 and 1.98 poses the diagnosis of pectus carinatum. [1]
PC commonly causes symptoms like dyspnoea and exercise intolerance but rarely cardiac and pulmonary dysfunction. Moreover, a disturbed body image, pain, psychological distress and thus reduced quality of life are consequences of this congenital anomaly. PC becomes evident in children, especially at the time of puberty, when the deformity becomes more conspicuous. Surgical treatment of PC significantly alleviates the symptoms. [1-4] Apart from the traditional surgical reconstruction, orthotic bracing has recently emerged as an alternative treatment option in selected patients. [2, 5]

Differential Diagnosis List

Final Diagnosis

Pectus carinatum (chondrogladiolar deformity type) in a patient with neurofibromatosis.

URL:	https://eurorad.org/case/12804
DOI:	10.1594/EURORAD/CASE.12804
ISSN:	1563-4086