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At a glance

It is an extremely rare progressive disorder in which portions of the bones of the arms and legs develop abnormally with unusual cartilage formations and subsequent abnormal bulbous metaphyses, ie, metaphyseal chondrodysplasia deformations. Affected individuals exhibit unusually short-limbed dwarfism. The onset of the disease becomes apparent typically during early childhood. Infants with Jansen-Type Metaphyseal Chondrodysplasia may have characteristic facial abnormalities and additional skeletal malformations. Hypercalcemia is present.

Synonyms

Jansen Metaphyseal Dysplasia; Murk Jansen Metaphyseal Chondrodysplasia; Chondrodysplasia Jansen type.

Incidence

Fewer than 25 cases have been reported in the literature.

Genetic inheritance

It is believed inherited as an autosomal dominant pattern. However, the majority of cases are the results of sporadic mutations.

Pathophysiology

Caused by mutation in parathyroid hormone receptor 1 gene (PTHR1), which has been mapped to 3p22-p21.1.

Diagnosis

Clinically evocated by the postnatal onset of severe short stature with joint dysfunction. Radiologic signs vary with age, showing diffuse radiolucency at birth, irregular calcification in childhood, and bulbous deformations of long bone extremities.

Clinical aspects

Severe short stature (adult height: 125 cm [49.2 inches]) and enlarged joints with flexion contractures (knees, hips). Affected individuals present a small thorax with kyphoscoliosis. Irregular and disorganized metaphyses associated with normal epiphyses are radiologically seen. The facial features include a small face with prominent supraorbital ridges, micrognathia, sometimes choanal atresia, high-arched palate, mandibular cyst. The presence of wide cranial sutures with hyperostosis of calvaria and cranial bone sclerosis are frequent. Variable degree of deafness is reported. Waddling gait. Biochemistry: Hypercalcemia, hypercalciuria, hypophosphatemia. Increased urinary cAMP; elevated 1,25(OH)2D3, alkaline phosphatase; low/absent parathyroid hormone.

Precautions before anesthesia

Assess renal function and serum calcium and phosphate levels. Hypercalcemia may be asymptomatic or may be associated with polyuria, dehydration, thrombosis, muscle weakness, and hyporeflexia. ECG is recommended. In the presence of symptomatic or clinically significant hypercalcemia, active steps should be taken to lower the serum levels (ie, with saline rehydration/diuresis). Phosphate supplementation may be required. Evaluate carefully the airway for potential difficult tracheal intubation (clinical, radiograph). Evaluate severity of the disease (clinical, full history, radiographs).

Anesthetic considerations

Only one anesthesia report has been published in the literature involving a 9-year-old child with Jansen Types Metachromatic Leukodystrophy (MLD). The facial features are suggestive of a potentially difficult airway management. One may expect face-mask ventilation to be a challenged. No doubt that direct laryngoscopy, and tracheal intubation may lead to complications such as “cannot ventilate, cannot intubate” type of scenario. It is highly recommended to maintain spontaneous ventilation at all time during induction of anesthesia and until the trachea has been secured and lung ventilation is confirmed. The availability of proper sizes laryngeal ...

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