X linked hypophosphatemia & Orthodontics #specialneedsdentistry

A child with x linked hypophosphatemia with OSA symptoms referred for orthodontics intervention. What are the important issues for the dental team?

Definition: x-linked hypophosphatemia is the most common hereditary form of hypophosphatemic rickets. The child will present with rickets due to renal phosphate wasting and  reduction of intestinal absorption of phosphate and calcium with the diminish production of 1,25‐(OH)₂ vitamin D.

The child may look like this:

Issues

Preoperative

a)Complications from XLH if poorly controlled

1          1. Open bite/ OSA requiring orthognathic surgery

-Delay in maxillary growth in relation to the growth of the mandible with skeletal class III tendency.

2.  Delayed bone healing

- Impaired bone remodelling with lack of bone mineralization in XLH

-Possibility of bisphosphonate use? Risk of BRONJ post op?

3. Spontaneous dental abscesses

-          IN XLH, the teeth exhibit enlarged pulp chambers with fissures that linked the enamel subsurface to the pulp horn due to globular dentin caused by hypophosphatemia which impairs calcification. Thus, the teeth are prone to develop dental abscesses requiring endodontic treatment.

-          Prevent by application of self-etching flowable composite sealants on teeth

-          It can happen during orthodontic treatment if, there is undesired heavy forces → pulp hyperemia → pulpitis → transient apical breakdown with periapical lesion (still reversible through revitalization) → pulp necrosis → apical periodontitis.

         4. Periodontal disease

-          Prior to starting orthodontic treatment, the periodontal health of the dentition should be established. There is increased risk of periodontal disease with severe attachment loss due to cementum aplasia or hypoplasia in XLH.

        5. Bone/joint pain due to osteomalacia, insufficiency fractures and osteoarthritis

-          They might be on long term NSAIDS. Thus, to check prior to prescribing analgesics

-          May affect TMJ?

       6. Hearing difficulties with mild-to-severe sensorineural hearing loss. Some patients also present with tinnitus and vertigo

-          Ensure patient is clear on risks of procedure (informed consent). Additionally, patient may be having high risk of falls in the ward if patient presents with vertigo.

b) We can assess Compliance to treatment by:

-Maintenance of acceptable height velocity and improvement in skeletal deformities generally indicate satisfactory dosing. Be aware that normalization of the serum phosphate is not what we are looking for as this can lead to secondary hyperparathyroidism.

c) Complication of treatment (Calcitriol)

-If overtreated, it can cause nephrocalcinosis (polyuria leading to dehydration). Thus, a renal profile with plasma calcium, PTH, creatinine and 24-h urinary calcium excretion is required

-  Patient may have hypercalcemia with features of kidney or biliary stones, bone pain, groans (abdominal pain, nausea and vomiting).

Perioperative

1. Risk of spinal cord stenosis leading to weakness/paralysis of upper and/or lower limbs

-During intubation, a prolonged hyperextension of the cervical spine can lead to compression of the spinal cord.

-Those who have X-linked hypophosphatemic rickets are at higher risk of this due to thickening of the vertebral laminae, facet joint hypertrophy, and ossification of the intervertebral discs, posterior longitudinal ligament, and/or ligamentum flavum.

2. Risk of bone fractures

-          Unfavourable bone fracture during orthognathic due to osteoporosis

Postoperative

Monitor vital signs (Pulse rate, spo2, respiratory rate, gcs)

-Severe hypophosphatemia may cause myocardial dysfunction, ventricular arrhythmias, rhabdomyolysis, seizures and altered mental status. They will first complain of skeletal muscle weakness particularly respiratory muscle.