Orofacial and Skeletal Manifestations of Hypophosphatemic Rickets in Fanconi Bickel Syndrome

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Figure 2a and 2b. Extra oral features

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Extra oral examination revealed brachycephaly, hypertelorism, broad nose, mid face deficiency (Figure 2a and 2b). Intraorally multiple missing teeth with poorly formed alveolar ridges were noted. Grade 1 and grade 2 mobility was present in many teeth(Figure 3a and 3 b).

Based on the skeletal findings, a provisional diagnosis of rickets with orodental manifestations was considered. Necessary investigations were advised and the patient was instructed to follow up with all the previous medical records before charting a treatment plan.

Figure 3a and 3b.

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Orthopantomograph revealed reduced height of maxillary and mandibular alveolar ridges with multiple embedded teeth in both jaws. Incomplete root formation and open apex of embedded upper and lower premolars and molars were appreciated. Other findings included rarefying osteitis in relation to periapical region of lower left canine and taurodontism in upper left first molar (Figure 4). In addition to the above findings, lateral cephalogram revealed severely deficient maxilla and true skeletal class III malocclusion with open bite (Figure 5).

Figure 4. OPG revealing multiple dental anomalies

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Figure 5. Lateral cephalogram reveals class III malocclusion and midface deficiency

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Figure 6. Hand wrist radiograph showing indicators of delayed skeletal development

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Hand wrist radiograph examination showed the absence of sesamoid bone in the proximal phalanx of 1^st digit and failure of fusion of epiphysis of proximal phalanx of 2^nd digit and middle phalanx of 3^rd digit (Figure 6). Knee radiograph revealed presence of radiopaque metal rods in femur and tibial bones suggestive of treated fractures (Figure 7).

Figure 7. knee X ray shows treated fracture of left and right tibial bone.

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During the patient’s first followup his medical reports were assessed which revealed the following data. At the age of 2 ½ years, patient had problems of developmental delay, poor weight gain, polyuria, abdominal distension, skeletal deformities, and recurrent respiratory infections. Ricketic features like open anterior fontanelle, fiddle shaped chest, Harrison’s sulcus, rachitic rosary, cat’s back, lateral bowing of fore-arms and legs; and glycogen storage disorder signs like protuberant abdomen with soft palpable liver was present. He was diagnosed to have FBS in his childhood and since then has been on treatment with neutral phosphate solution, calcirol granules and alkali solution. Childhood history of treated case of fractured leg was also present. His present biochemical reports of serum electrolytes, calcium and phosphates, urine and serum creatinine were within normal limits.

Thus with the childhood illness reports, clinical signs and symptoms and radiological investigations, we came to the final diagnosis of oral manifestations of hypophosphatemic rickets in FBS. The oral manifestations included all the features listed in Table 1.

Table 1. clinical, radiologic and histological dental findings in our patient

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The patient is currently under the medical management of alkali solution, calcirol granules and neutral phosphate solution.

Dental management: Our patient was counseled and educated on the maintenance of good oral hygiene. He underwent a thorough oral prophylaxis. Mobile lower left lateral incisor was extracted and subjected to histopathological examination which revealed the presence of interglobular dentin. On subsequent visit, cusp tip of lower left canine was appreciated clinically at this age of 17 years. The patient at present is under regular follow up.

3. Discussion

Fanconi syndrome is a systemic, autosomal recessive, inherited syndrome usually resulting in proximal renal tubular acidosis (RTA), of which FBS is one of the entity. ^[1] FBS, has also been known as hepatorenal glycogenosis with renal Fanconi Syndrome and categorized under Glycogen Storage Disease Type XI represents an extremely rare disorder. ^[2] In 1949, Guido Fanconi and Horst Bickel described it for the first time. ^{[2, 3]} According to Santer et al, a total of 109 cases in 88 families have been reported. ^{[3, 4, 5]} Reported cases are mainly from all parts of Europe, Turkey, Israel, Arabian countries of the Near East and North Africa, Japan, and North America. ^[2] Search in Pubmed for “oral manifestations of FBS” yielded a result of only one such reported case. Parental consanguinity was present in index case and the literature suggests its presence in 2/3rd of patients of FBS ^{[4, 5]}.

Features typical to FBS presents with variable degrees of manifestations of hypophosphatemic rickets, RTA, and hepatomegaly resulting from GSD XI. ^[6] Hypophosphatemic rickets in Fanconi syndrome presents with failure of production of 1,25-dihydroxy vitamin D from its precursor 25-hydroxy vitamin D and defective resorption of phosphate in the proximal renal tubule. ^[7] This causes imbalance primarily in bone metabolism and forms the basis for all skeletal and dental morbid features. Its prevalence is approximately 1 in 20,000 ^[7]

Pathophysiology of FBS has been well explained in the previous articles ^{[8, 9]} The underlying pathology of bone disease in FBS has been simplified and explained by two distinct mechanisms as shown in Figure 8 ^{[8, 9]}.

Figure 8. shows the flowchart explaining the pathophysiology of bone disease in rickets

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Hypophosphatemia in FBS results in hypoplasia and deficient calcification of mineralized structures such as bones and teeth. Among various types of rickets, hypophosphatemic rickets presents mainly with dental manifestations. ^[10] The skeletal and dental manifestations of hypophosphatemic rickets have been enumerated in Table 2 and Table 3 ^{[7, 11, 12]}.

Table 2. skeletal manifestations of hypophosphatemic rickets

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Table 3. Dental manifeatations of hypophosphatemic rickets

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Craniofacial features and various dental abnormalities helps the oral physician to discover underlying systemic disease/ syndrome.. Some of the oral/dental and characteristic skeletal features has been described in the Table 4. ^{[13, 14, 15]} Knowledge of such presentations helps in early diagnosis and management of systemic disease /syndrome thus reducing the morbidity of disease and improving the quality of life.

Table 4. Few differential diagnosis simulating the orofacial and skeletal manifestations similar to the present case

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