Osteopoikilosis in the Mandible

Abstract

Osteopoikilosis (OPK) is a rare benign bone dysplasia characterized by the presence of multiple radiodense patches scattered throughout the skeleton’s trabecular bone. It presents as small well-demarcated bone lesions of variable sizes and of a sclerotic nature. OPK is a benign bone pathology that requires no treatment but monitoring and management of possible symptoms. This case highlights the incidental finding of an asymptomatic OPK in the mandible of a patient seeking orthodontic treatment; OPK manifestation in the mandible was rarely reported before. Radiologic and clinical diagnoses, along with the family history, confirmed the differential diagnosis of OPK. Such a differential diagnosis includes a range of serious conditions such as osteoblastic metastasis and tuberous sclerosis, making the correct diagnosis of OPK essential for overtreatment prevention. Treatment consisted of patient education, follow-up, and anti-inflammatory drugs in case of symptomatic flare-ups. This article reports on a case of OPK presenting lesions in the mandible as well as in other bones of the skeleton; such a manifestation of OPK in the cranium and specifically in the mandible is considered extremely rare.

Introduction

Osteopoikilosis (OPK) is a rare benign sclerosing bone dysplasia characterized by the presence of multiple radiodense patches or streaks scattered throughout the skeleton’s trabecular bone.[1] It is caused by a failure of resorption of secondary spongy bone.[2,3] Due to its rare occurrence with an incidence of approximately 1 in every 50,000 individuals, it is a fairly unknown condition with a male predilection and a mostly autosomal dominant pattern of inheritance.[4,5] It is usually incidentally found in the second to third decades of life through radiographs of an affected area, presenting as small well well-demarcated, round or ovoid symmetrical bone lesions of variable sizes and of sclerotic nature.[4,6] It is often asymptomatic,[7] however, it is sometimes associated with skin manifestations and joint pain or stiffness. It predominantly affects phalanges (100%), carpals (97.4%), metacarpals (92.5%), tarsals (84.4%), metatarsals (84.4%), pelvis (74.4%), and long bones, especially radius (66.7%) and ulna (66.7%).[8] Lesions may also involve the ribs and clavicles. Cranial involvement has been rarely documented, and even more unusual is the mandibular involvement, as presented in this case report.[9,10] OPK is a benign bone pathology that has a good prognosis as it requires no treatment but only monitoring and management of possible symptoms.[11,12] The differential diagnosis is established with osteoblastic metastasis, osteopathia striata, mastocystosis, and tuberous sclerosis.[11,12] Therefore, it is important to establish a proper diagnosis to prevent unnecessary alertness of the patient and overtreatment.

Case Report

A male, 16 years of age, presented for an orthodontic consultation at a private clinic. The patient’s chief complaint was the impacted maxillary left canine.

Pretreatment extraoral photographs [Figure 1] showed a concave subnasal profile with an increased nasolabial angle, a strong chin, and thin lips. Upon smiling, only 50% of the maxillary anterior teeth were showing. Pretreatment intraoral photographs [Figure 1] revealed a Class I occlusion along with a deep bite. The primary maxillary left canine was retained, and the mandibular anterior crowding was severe.

Figure 1.

Pretreatment extraoral and intraoral photographs

Radiographically [Figure 2], the pretreatment lateral cephalogram showed a skeletal class II with a retrognathic mandible, a hypodivergent pattern, and retroclined maxillary incisors. On the handwrist radiograph, multiple round and well-demarcated radiopaque lesions were seen at the level of the carpals and metacarpals. The pretreatment panoramic X-ray showed a horizontally impacted maxillary left permanent canine. It also showed multiple bony lesions between the root apices of the mandibular molars. These radiographic findings were alarming and led to further investigations.

Figure 2.

Pretreatment X-rays: Lateral cephalogram, hand-wrist X-ray, and panoramic

The orthodontic treatment plan was a nonsurgical treatment with extraction of the impacted canine, followed by space closure to finish in Class I on the right side and full Class II molars on the left side.

A cone-beam computed tomography X-ray (CBCT) [Figure 3] of the mandible was taken to diagnose the bony lesions seen on the panoramic and the handwrist radiographs. The CBCT revealed multiple benign bony islands/enostoses scalloping between the roots of the mandibular teeth. The differential diagnoses included OPK, osteobastic metastasis, and tuberous sclerosis. Further investigation of the family history revealed the earlier diagnosis of the mother with OPK over a handwrist X-ray taken after a trauma. The diagnosis of OPK was then confirmed. The orthodontic treatment was initiated normally, and the patient and his parents were informed of the OPK diagnosis. They were instructed to follow-up regularly and to control flare-ups with anti-inflammatory drugs. OPK in the mandible has been documented only once in the literature,[9] making this case an extremely rare case of OPK.

Figure 3.

Pretreatment CBCT cuts showing the osteopoikilotic lesions in the mandible

Discussion

OPK is a rare bone dysplasia with an autosomal dominant pattern of inheritance and an unclear pathophysiology. However, publications describe a mutation of the LEM domain-containing gene 3 as the possible cause of the dysplasia, occurring either sporadically or inherited genetically.[11,13] This gene is important for the maturation of endochondral bone, where its mutation leads to bone sclerosis, highly resembling enostosis on radiographic images.[11,14,15]

In most cases, the diagnosis of OPK is incidental as the bone lesions are usually asymptomatic in nature. However, about 15%–20% of patients report joint symptoms, including joint pain and effusion.[1] Moreover, 25% of patients suffer cutaneous manifestations, such as dermatofibromas defined as Buschke–Ollendorffsyndrome,[13,16] discoid lupus erythematous, or keloids.[11,17] Studies further report the association of OPK with scleroderma, endocrinological diseases, osteochondromatosis, ankylosing spondylitis, rheumatoid arthritis, syndactyly, and cleft palate, among other diseases.[18,19] However, significant mutual influence of these diseases has not been proven.[20]

Several differential diagnoses intercept with that of OPK, including tuberous sclerosis, Paget’s disease, mastocytosis, osteopathia striata, melorheostosis, synovial chondromatosis, sesamoid ossicles, and Ollier’s disease, and most importantly, osteoblastic metastasis.[18] The gravity of osteoblastic metastasis underlines the importance of its proper diagnosis and discordance. Radiologically, OPK presents as symmetrical focal lesions of uniform size without any cortical erosion, unlike the asymmetrical lesions of osteoblastic metastases of variable sizes that may lead to subcortical destruction.[21,22] In fact, due to the radiodense islands of OPK, the surrounding bone appears relatively more radiolucent than normal trabecular bone. Further complementary tests, such as blood tests of alkaline and acid phosphatase and bone scintigraphy with Tc-99 m radionuclide scan, are typically normal in OPK,[11,18,21,23] although pathologic findings of the latter have been reported in the literature in young OPK patients, possibly due to bone remodeling.[24] OPK is considered a “do not touch” lesion, where further invasive procedures such as biopsies are contraindicated as they are unnecessary or may cause harm to the patient.[11,25] Possible but very rare complications of OPK include osteosarcoma,[26] giant cell tumor, and chondrosarcoma,[27] which require regular follow-up throughout the patient’s life.

In the present case, investigating the patient’s and the mother’s medical history, clinical manifestations, and radiographic images was substantial for the proper diagnosis, and thus, no further testing was needed. The patient was educated by a specialist on the subject and of the possible future manifestations and complications and was instructed to use anti-inflammatory drugs or analgesics in case of possible painful flare-ups.[12]

The occurrence of OPK in the mandible is considered extremely rare and was rarely reported in the literature. Due to its rarity, this case is considered significant for its unique nature and the potential insights it can provide into the disease’s diagnosis and treatment. Further reporting and research are important for the establishment of a clear protocol to help in the diagnosis of OPK in the mandible.

Conclusion

Being a benign sclerotic bone dysplasia, OPK requires a proper diagnosis to rule out other more serious differential diagnoses, notably osteoblastic metastases. Atypical locations such as the mandible might falsely alert both the physician and the patient, leading to unnecessary testing and overtreatment.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that his name and initials will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed.

Conflicts of interest

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Funding Statement

Nil.