Case of bilateral hip joint Charcot arthropathy in a paediatric patient

Background

The term ‘hereditary sensory and autonomic neuropathies’ (HSAN) refers to a group of inherited diseases characterised by sensory and autonomic dysfunction in varying degrees.1–3 Additional entities are still being described after Dyck and Ohta’s numerical classification of four different types of HSAN, therefore, the process of identifying and classifying new things is still ongoing.4 HSAN type 4 or congenital insensitivity to pain with anhidrosis (CIPA) is a very rare autosomal recessive condition. The pathogenesis of HSAN-4 is due to dysfunction in NGF-dependent neurons whose target organs typically contain TrkA.5 The interaction between NGF and TrkA, a neurotrophic factor, is necessary for the survival and upkeep of NGF-dependent neurons.6

Early symptoms of this condition include biting of the tongue and lips, bone fractures, and painless joint dislocations in infants between the ages of birth and three. Its diagnosis should be suspected in early childhood with excoriated lesions of the extremities (ungual and cutaneous with osteolytic lesions), stomatological involvement starting in the first year of life when the first teeth appear, and excoriated lesions of the extremities.1 7 Other typical clinical manifestations include anhidrosis, sensitivity to noxious stimuli leading to self-mutilating behaviour, fractures, dry skin, multiple injuries and intellectual impairment.8

Studies on gait have revealed that HSAN-4 and HSAN-5 patients have faster gait and greater heel contact angular velocity than controls, which may result in a stronger contact force and explain the traumas to the lower extremities.3 9 Traumatic fractures are frequent and bone disintegration occurs due to the affected nociceptive and proprioceptive innervation of the joint which eventually results in a Charcot joint.8 10

The clinical characteristics, the level of sensory and autonomic dysfunction, metabolic analyses, and pathological tests all contribute to the diagnosis. Patients with HSAN type IV can be given only supportive care as there is no cure and require care from a multidisciplinary team. We present a case report of a paediatric patient with bilateral hip joint Charcot’s arthropathy and images showing the clinical traits.

Case presentation

An adolescent girl was referred to our hospital with swelling in both the thighs and difficulty in walking for 2 months. There was no specific preceding trauma. The parents of the child gave a history of swellings around the knee and ankle joints in the past. They also gave a history of frequent episodes of fever, particularly when the ambient temperature is more in the summer seasons. There was also a history of spontaneous amputation of one of the toes in the left foot 2 years ago (figure 1).

On examination, the patient’s vitals were normal and there were no signs of pallor, icterus, cyanosis, clubbing, lymphadenopathy and generalised oedema. Cardiovascular, respiratory and per-abdominal examinations were normal. Supernumerary teeth are present (figure 2A,B). Multiple hyperpigmented scars and macules were present (figure 3A–C). Trident hand was noticed bilaterally, that is, a hand in which the fingers of nearly equal length deflected at the first interphalangeal joint to give a forklike shape consisting of separation of the first and second as well as the third and fourth digits (figure 4A,B). There were signs of self-mutilation in the form of ulcerations of the lower lip, tongue and oral mucosa. Skin, especially over the palms and soles was dry, coarse and mildly hyperkeratotic. Neurological examination revealed a generalised absence of response to temperature and painful stimuli. Touch, position and vibration senses were intact. Tendon reflexes and plantar responses were normal.

The patient had a waddling gait. Diffuse swelling was noted around the proximal thigh bilaterally with exaggerated lumbar lordosis (figure 5). Movements of both hips were exaggerated and painless. The bilateral telescopy test was positive (figures 6A,B, 7A,B). There was also a widening of the ankle physis (figure 8).

Investigations

Plain radiographs of the pelvis with both hips showed dislocation of both hip joints with proximal migration of femoral heads. There was evidence of erosions, shallowing of acetabular margins and bony fragments(figure 9).

Plain and contrast MRI of bilateral hip joints showed right hip moderate and left hip gross joint effusion with minimal thickening and enhancement of the synovium, extensive inflammatory changes with intramuscular collections in the muscles around the right hip joint. There was a posterosuperior dislocation of bilateral hip joints (L>R) with irregularity and mild reduction in the height of the proximal epiphysis of the left femoral head, sclerosis of the bilateral acetabulum with loss of normal contour. Nerve conduction study was suggestive of symmetric sensorimotor axonal neuropathy involving all the limbs. A bedside sweat test using prilocaine showed total absence of sweating. Ophthalmic examinations revealed features of neurotrophic keratopathy with corneal ulcers in both eyes (figure 10).

Differential diagnosis

Charcot arthropathy or neuropathic arthropathy of the bilateral hip joint is a rare entity. Common causes of neuropathic arthropathy are diabetes mellitus, syringomyelia and syphilis. Less common causes include leprosy, demyelinating peripheral neuropathies, alcoholism and repeated corticosteroid injections.

Charcot arthropathy associated with diabetes mellitus commonly involves midfoot and can be easily diagnosed with blood tests showing altered glycaemic control. Syringomyelia commonly causes arthropathy in the upper extremity. Neuropathic arthropathy related to neurosyphilis involves the lower limbs, affecting most commonly the knees, followed by the hips and ankles and it is seen in the sexually active age group.11 Arthropathy associated with leprosy will have associated features of skin lesions, thickened peripheral nerves or nerve abscesses, etc.

Alcoholism and repeated corticosteroid injection can be attributed to aetiology by eliciting meticulous history.

Our case had all the classical features of HSAN type 4 like self-mutilation features, neurotrophic keratopathy, dental problems, autoamputation toes, anhidrosis and painless destruction/dislocation of joints.

Anhidrosis leading to coarse skin features and frequent fever episodes in increased ambient temperature settings, absence of tears leading to neurotrophic keratopathy and the onset of symptoms from infancy, and findings of nerve conduction studies helped us to differentiate type 4 from other subtypes of HSAN. Even though genetic evaluation helps in confirming the subtype of HSAN, it has no prognostic value and hence was not carried out.

Treatment

The patient was treated conservatively. The parents were educated about the syndrome and explained the prognosis. The child was given calcium and vitamin supplements. The patient and parents were advised to take measures to avoid excessive impact on joints, including the usage of protective footwear. The patient was advised to tape the eyelids while sleeping and to use eye-drops at regular intervals while awake to mitigate neurotrophic keratopathy. She was advised to use tepid sponging to avoid frequent fever episodes whenever the ambient temperature was high.

Outcome and follow-up

The patient is currently under regular follow-up and is undergoing physiotherapy. Parents have been educated regarding the nature of the disease