Scalp nodules as a presenting sign of fibrodysplasia ossificans progressiva: a register-based study

Scalp Nodules and Deformed Great Toes: Omens of Fibrodysplasia Ossificans Progressiva

ABSTRACT

We report a case of fibrous scalp nodules and bilateral hallux valgus in an infant who one decade later was diagnosed with a rare life-threatening genetic disease.

A Clinical Perspective on Advanced Developments in Bone Biopsy Assessment in Rare Bone Disorders

Introduction: Bone biopsies have been obtained for many centuries and are one of the oldest known medical procedures in history. Despite the introduction of new noninvasive radiographic imaging techniques and genetic analyses, bone biopsies are still valuable in the diagnosis of bone diseases. Advanced techniques for the assessment of bone quality in bone biopsies, which have emerged during the last decades, allows in-depth tissue analyses beyond structural changes visible in bone histology. In this review, we give an overview of the application and advantages of the advanced techniques for the analysis of bone biopsies in the clinical setting of various rare metabolic bone diseases. Method: A systematic literature search on rare metabolic bone diseases and analyzing techniques of bone biopsies was performed in PubMed up to 2019 week 34. Results: Advanced techniques for the analysis of bone biopsies were described for rare metabolic bone disorders including Paget's disease of bone, osteogenesis imperfecta, fibrous dysplasia, Fibrodysplasia ossificans progressiva, PLS3 X-linked osteoporosis, Loeys-Diets syndrome, osteopetrosis, Erdheim-Chester disease, and Cherubism. A variety of advanced available analytical techniques were identified that may help to provide additional detail on cellular, structural, and compositional characteristics in rare bone diseases complementing classical histopathology. Discussion: To date, these techniques have only been used in research and not in daily clinical practice. Clinical application of bone quality assessment techniques depends upon several aspects such as availability of the technique in hospitals, the existence of reference data, and a cooperative network of researchers and clinicians. The evaluation of rare metabolic bone disorders requires a repertoire of different methods, owing to their distinct bone tissue characteristics. The broader use of bone material obtained from biopsies could provide much more information about pathophysiology or treatment options and establish bone biopsies as a valuable tool in rare metabolic bone diseases.

Fibrodysplasia ossificans progressiva: initial presentation with a preosseous lesion of the scalp and its MRI appearance

This case subject is a 1-year-old girl presenting with recurrent diffuse soft-tissue swelling of the scalp and periorbital region. Her family denied any known history of trauma. There was no obvious discoloration or local heat at the lesion. Magnetic resonance imaging (MRI) revealed diffuse soft tissue swelling of the scalp manifesting as high signal intensity on T2-weighted images and low signal intensity on T1-weighted images with diffuse enhancement after gadolinium-contrast administration. Biopsy yielded inconclusive pathological results. Fibrodysplasia ossificans progressiva (FOP) was not suspected until malformation of the patient's toes was noticed. The scalp lesion underwent spontaneous regression, and subsequent radiographs of the chest and cervical spine revealed heterotopic ossifications of the neck and thorax. Early diagnosis of FOP is vital because trauma, unnecessary biopsy and intramuscular injection are known to cause acceleration of heterotopic ossifications. Previous studies reported diffuse soft tissue swelling at the posterior neck, thoracic wall or paraspinal region as preosseous lesions of FOP (Shiva Kumar et al. Neurology. 2010;74(6):e20, Merchant et al. Pediatr Radiol. 2006;36(10):1108-11, Hagiwara et al. AJR Am J Roentgenol. 2003;181(4):1145-7). To our knowledge, diffuse soft tissue swelling of the scalp as a preosseous lesion of FOP and associated MRI findings have not yet been reported. We believe that awareness of preosseous lesions presenting as diffuse soft tissue swelling, in addition to shortening and valgus deformity of the great toes, is an important diagnostic clue for establishing FOP.