History and highlights of the teratological collection in the Narrenturm, Vienna (Austria)

The collection of the Narrenturm in Vienna houses and maintains more than 50,000 objects including approximately 1200 teratological specimens; making it one of the biggest collections of specimens from human origin in Europe. The existence of this magnificent collection―representing an important resource for dysmorphology research, mostly awaiting contemporary diagnoses―is not widely known in the scientific community. Here, we show that the Narrenturm harbors a wealth of specimens with (exceptionally) rare congenital anomalies. These museums can be seen as physical repositories of human malformation, covering hundreds of years of dedicated collecting and preserving, thereby creating unique settings that can be used to expand our knowledge of developmental conditions that have to be preserved for future generations of scientists.

the past, considered as "cabinets of curiosities" that get most of their attraction from their potential horrification and morbid appeal.
Instead, a modern display of human malformations should be question-inspiring and thought-provoking, thereby creating ground for extended inquiry (Boer, 2019). Solely exhibiting teratological specimens without any validated thought or message somehow explicitly implies that visitors are forced into its morbid aspect which is inherently present in any collection of human origin (Boer, de Rooy, et al., 2021). To overcome this "Wunderkammer" effect and to create a meaningful exhibition for visitors, experts and laymen alike, the first step is to communicate up-to-date medical and etiopathogenetic backgrounds of the anomalies that are being exposed or curated. By doing so its museal validity revives, legitimizing conservation and exhibition of these specimens. In addition, most teratological collections house a number of exceptionally rare anomalies-with inherently valuable etiopathogenetic clues-that are worth being described in more detail, as they often represent typical depictions of disorders.
Moreover, some of these anomalies potentially provide critical information in certain etiopathogenetic thoughts or quests (Boer, Schepens-Franke, et al., 2021;Oostra et al., 2022). This article describes both the history of the Narrenturm itself as its teratological highlights. We give an overview of the sheer magnitude of this teratological pinnacle and describe 28-mostly syndromic-cases in further detail, including some exceptionally rare conditions.

| THE ORIGIN OF THE NARRENTURM
Before the end of the 18th century, those who were mentally ill became ostracized from society and were not regarded as treatable patients. This changed in 1784 when the Narrenthurm or Irrenthurm (Tower of Fools, currently spelled Narrenturm), part of the kaiserlichköniglich Irrenanstalt zu Wien (imperial insane asylum of Vienna, Austria) was built ( Figure 1). This early Classicist style psychiatric asylum is Vienna's first building for the accommodation of psychiatric patients and dedicated solely to caring for the mentally disabled, who until then were oftentimes caged, as the true nature of psychiatric illness was still largely unknown (Gabriel, 2020). Imprisoning the "fools" was done to protect society and it was not until the second half of the 18th century that they were increasingly seen as patients which might and could be cured (Houston, 2020). However, the Narrenturm was still more a retaining facility rather than an institution to heal and still shaped like a "cage." Commissioned under the reign of the enlightened Holy Roman Emperor Joseph II (1741-1790), eldest son of Empress Maria Theresia and her husband, Emperor Franz I, the Narrenturm consisted of a five-story fortress-like circular building with 139 cells to accommodate 200-250 patients. The Narrenturm-at the time a state-of-the-art building with heating and sewer system-was part of the newly constructed General Hospital of Vienna. The Narrenturm points out a new attitude and symbol of progress toward the mentally ill. They became distinguished from the rest of society, implying that they were not anymore classified among the general category of "the poor." A shifting perception preponderated that of those who were mentally unstable were in fact ill and required medical treatment. However, the relatively isolated Narrenturm with its barrack-like appearance, was a visible reminder for society to the expression of the segregation, criminalisation and stigmatization of deviant forms of social behavior. Nevertheless, erection of the Narrenturm helped to make psychiatry a medical discipline of its own.
Within the scope of the new General Hospital also came the need for medical teaching. To facilitate this, a teaching hospital and medical-surgical academy opened in 1787. The Narrenturm, which until 1869 served as an institution for the mentally ill, subsequently became in use as an archive and nursing home. It became superfluous after this period and converted to a protected landmark in 1923. It was not until 1971 that the building was put in use to store the pathological and anatomical collections of the General Hospital. The first attempts to realize these collections-aiming to aid the teaching of students and physicians who worked at the hospital-date back to the second half of the 18th century (Hausner, 1998). In 1974, the specimens, including the administration of the collections, which had always been mandated by the University Institute of Pathology, fell F I G U R E 1 Left: building plan of the Narrenturm which was erected in 1784. Right: photograph taken around 1920 in which the Narrenturm is seen in the background.

| THE INITIAL COLLECTORS OF PATHOLOGICAL AND ANATOMICAL SPECIMENS
The first academically acquired pathological specimens in Vienna must have been collected around 1754 by the Dutch professor and first director of the medical clinic in Vienna, Anton de Haen (1704-1776.
De Haen was an advocate of post-mortem investigations and the first museal preparations probably originated from these autopsies.
Although most of these early specimens got lost over time, one of the oldest specimens present in the collection concerns the body of a 3-year-old taxidermized girl described as being affected by ichthyosis vulgaris originating from around 1780 ( Figure 2). The larger part of the extant collection finds its origin in the late 18th century when plans were made to create an entire new grand hospital to house up to 2000 patients (Hausner, 1998). German physician and hygienist Johann Peter Frank (1745Frank ( -1821

became director of this General
Hospital and head of the medical clinic in 1795 (Frank, 1802). Frank took it upon himself to collect as many pathological specimens as possible and cooperated with municipal physician Pascal Joseph von Ferro (1753Ferro ( -1809 to achieve this goal. Shortly after, the establishment of a pathological museum at the General Hospital was initiated.
All physicians were ordered to prepare, collect and store specimens with extraordinary anomalies and pathologies from all sectors of medicine (Hausner, 1998). However, physicians charged with performing autopsies and the subsequent collection of specimens, showed little enthusiasm for this laborious task. To fulfill Frank's desire to create a pathological-anatomical collection at the university of Vienna, a dedicated prosector, Aloys Rudolph Vetter (1765Vetter ( -1806, was appointed in 1796. Together with the foundation of a pathologic-anatomical institute in that same year, the beginning of a collection-that would grow to enormous proportions-was a fact . Vetter became the first official prosector, who was, although unpaid, burdened to execute the pathological autopsies and to archive the obtained specimens. Frank's ultimate goal was to build a spacious mortuary and a separate room dedicated for autopsies. One of the aims was to produce and preserve specimens from patients who had died of particularly interesting diseases. As instructed by Frank (1802), records of these clinical autopsies were written down meticulously with more than 500,000 documented cases from Vienna starting at 1817. Many of these reports concern dissections done at the new General Hospital of Vienna . With continuous zeal and diligence on an almost industrial level Vetter collected a considerable amount of pathological specimens. In his "Aphorismen aus der Pathologischen Anatomie" (Aphorisms of Pathological Anatomy) Vetter stated that within 5 years of his stewardship the collection had grown to 400 specimens (Bankl, 1997;Vetter, 1803). After Vetter retired in 1803, Frank followed suit in 1804. Aloys Michael Mayer (1766-1831 who was appointed to the anatomical chair in 1791 was charged ex officio with performing autopsies and preserving interesting specimens after Frank left. However, Mayer had only minimal contributions to this obligation. In 1812, Laurenz Biermayer (1778-1843) followed Mayer and became the first paid prosector specifically assigned to perform autopsies and steward its growing collection. Annually, he performed more than 600 (forensic) autopsies and made preparations of interesting specimens which were included in the Pathological-Anatomical Collection . In 1813, Biermayer started to retrospectively catalogue the museal collection and described 484 specimens. In 1816, this work was printed in Latin: ""Musaeum Anatomico-Pathologicum Nosocomii Universalis Vindobonensis" (Biermayer, 1816). He also catalogued the specimens that he had acquired himself in a work entitled: "Catalogus preaparatorum in Museo pathologico adservatorum," which was indexed to 4307 specimens when he last signed an entry in 1827. Besides the wealth of F I G U R E 2 Taxidermized body of a 3-year-old girl described as being affected by congenital ichthyosiform erythroderma originating from around 1780.
preparations, his achievement in describing the collection and registration of dissection protocols were of such merit that he was appointed as extraordinary professor of pathological anatomy in 1821 . In 1828, he published a book in which 576 particularly remarkable specimens from the Pathological Museum were described (Biermayer, 1828). Unfortunately, Biermayers' unfettered favor for alcohol made him resign in 1831 (Hausner, 1998). When

Biermayer became dismissed after another inebriation it was Johann
Wagner (1800-1832)-Biermayer's assistant since 1829-who advanced to museum director and chair of anatomy. More than 1000 autopsies per year were performed under his supervision and the museal catalogues indexed 4822 specimens upon his death in 1832 (Hausner, 1998). During Wagner's employment the dissecting rooms also served as a working place for Carl von Rokitansky (1804Rokitansky ( -1878 who was accepted as an unpaid intern of Biermayer in 1827. Rokitansky subsequently became Wagner's assistant in 1831 which was the start of immortal fame for both the institution and himself, since Rokitansky is seen as the trailblazer of modern pathology (Andree, 2004;Sedivy, 2004a). Subsequent years of academic growth let to the appointment of Rokitansky to become full professor in pathological anatomy between 1844 and 1847 in which he dissected more than 1000 bodies per year. In 1827, his autopsy reports started with register number 4781 (Biermayer's last acquisition) and stopped with an astonishing 64,567 autopsies in 1875 (Bankl, 1997;Winter et al., 2013), which reflects the monumental rise of pathological anatomy as a medical discipline.
F I G U R E 3 Specimen MN9527 of a small intestine of a 23-yearold male diagnosed with diathesis aneurysmatica (a hereditary or constitutional predisposition for aneurysms) dated January 13, 1849, collected by Rokitansky. This disease is known as Periarteritis nodosa (PAN) or Kussmaul Maier disease, ORPHA 767 (Sedivy, 2004b).
F I G U R E 4 Examples of repositories in the Narrenturm in which the specimens are kept. Although fairly grouped by their morphology and/or anomaly, many specimens were never looked at with a modern dysmorphological approach.
T A B L E 1 Teratological diagnoses made in the specimens of the Narrenturm collection.  According to the classification of Opitz and Gilbert (1982) complex malformations concern one organ or organ system while multiple malformation of different organs are defined as associated malformations (in contrast to syndromic and sequential malformations). b Neural tube defects (NTD) are restricted to the closure defects of the neural tube. Holoprosencephaly (HPE) is defined as "CNS malformations" due to failure of forebrain cleavage. Iniencephaly is a malformation of the cervical spine but often associated with cranioschisis. Otocephaly is a craniofacial (1st branchial arch) malformation. It may or may not be associated with HPE, NTD and other organ malformations but is not so closely related to HPE as the so called facial midline defects.
In 1862, a new building was erected to increase the capacity of the autopsies; the Pathological-Anatomical Museum moved to this building and belonged to the institute run by Rokitansky who selected 1375 original museum specimens to be included. Shortly after, the new building housed 5000 high quality specimens, collected by Rokitansky, for research and teaching purposes (Hausner, 1998). Currently, a number of original specimens from Rokitansky are still in the collections of the Narrenturm (Figure 3). Throughout many subsequent years Rokitansky's successors were all curators of the museum and its collections which they aimed to increase with specimens that reflected their own interests (Hausner, 1998;Patzak et al., 2013). In 1970, the museum of the Pathological-Anatomical Institute housed more than 14,000 anatomical, pathological and teratological specimens. Currently, the Narrenturm comprises more than 50,000 objects, including some 36,000 wet preparations, 10,000 macerated specimens, 200 (partial) skeletons, thousands of skulls and 3300 moulages, originating not only from the Pathological-Anatomical Museum but also from numerous adopted collections . Most teratological specimens acquired after Rokitansky originate from the two gynecological university hospitals and the city hospitals of Vienna. Undeniably, the Narrenturm houses one of Europe's largest medical collections, which is a treasure chest for both historical, pathological and teratological research (Boer, Schepens-Franke, et al., 2021).

| MATERIALS AND METHODS
According to the collection registers approximately 1200 of the 50,000 objects concern specimens of human malformations, although the actual number may be higher since some conditions may not have been recognized as such and instead were registered as acquired disorders. During a 3-day survey, we revisited >80% of these specimens ( Figure 4) and prepared a preliminary diagnostic inventory of the conditions they presented, which were discussed with the local colleagues. Although the enormous amounts of post-mortem reports, medical information concerning malformations was mostly lacking or restricted to what was written on the labels. Most specimens, except for dried skeletons, were stored in closed glass containers. To minimize the risk of damaging the specimens, these containers had to be kept closed, unless it was highly plausible that closer inspection of the content and/or additional imaging (X-ray, CT) would yield essential diagnostic information Furthermore, in a single case histology was performed to narrow the differential diagnosis.

| RESULTS
In the approximate 1000 specimens that we inspected a total of over 70 different diagnoses were made which are listed in Table 1 in four arbitrary categories. Conditions were listed as "syndromic" if the perceived malformations could be diagnosed as such with a reasonable degree of certainty; if not they were listed as "non-syndromic," which included isolated, complex and associated conditions. Developmental defects of the neural tube and pathological twinning formed the two remaining categories. We made a selection of some remarkable-mostly syndromic-cases, which are described in more detail below (see cases 1-28).
The presence of the specific hitch-hiker's position is highly suggestive for a group of skeletal dysplasias that are caused by defects in sulfate metabolism, which was reviewed by Paganini et al. (2020), that is, those pertaining the diastrophic dysplasia sulfate transporter (DTDST) due to pathogenic variation in the SLC26A2 gene. Considering the shortness of the limbs, especially of the upper arms, the apparent fullterm development and neonatal lethality, autosomal recessive "atelosteogenesis type 2" (OMIM 256050) seemed to be the most likely diagnosis in this case. X-ray confirmed this diagnosis and revealed shortness of tubular bones, especially of the femora with narrow and cupped distal metaphyses, bifid distal humeri, dysplastic fibulae, small ribcage, platyspondyly, scoliosis, lumbar lordosis, and talipes equinovarus ( Figure 7c). Atelosteogenesis type 2 is allelic not only to diastrophic dysplasia (OMIM 222600), but also to achondrogenesis type 1b (OMIM 600972) and multiple epiphyseal dysplasia type 4 (OMIM 226900) (Superti-Furga & Unger, 1993).

| Case 4. Boomerang dysplasia
Specimen MN21.055/265 concerns a dried neonatal skeleton presenting with severe short-limbed dwarfism, dated 1887 ( Figure 8a). The original diagnosis was "congenital hydrocephalus with shortening of the extremities and congenital rickets." On examination a neonatal skeleton is seen with a relatively large head, midfacial and mandibular underdevelopment, severe symmetrical micromelia, and boomerang-like bowing of the long tubular bones, especially of the femora, radii, and ulnae. Interestingly this specimen was investigated with X-rays by Beighton et al. (1993), who diagnosed it as thanatophoric dysplasia, based on the presence of "telephone receiver" shaped femora, horizontal acetabula, and marked platyspondyly, with "H-shaped", poorly ossified vertebral bodies (Beighton et al., 1993(Beighton et al., , 2005. Re-examination of this specimen together with a repeated radiological investigation confirmed the previous finding but Figure 8b additionally disclosed a more generally diminished ossification. Furthermore, focally disorganized bone structures were seen in the vertebral bodies and limb bones, especially in the femora and tibiae. This, together with the boomerang aspect of the distinctly shortened tubular bones, presents a characteristic feature of an FLNB-related skeletal disorder (Kozlowski et al., 1985;Robertson, 1993;Wessels et al., 2003). We thus consider a correction of the diagnosis from "thanatophoric dysplasia" to autosomal dominant "Boomerang dysplasia" to be justified (OMIM 112310).

| Case 5. Brooke-Spiegler Syndrome
This tumors that histologically include cylindromas, trichoepitheliomas and spiradenomas with a preference for the head and neck region. It predominantly affects women, with a male to female ratio of 1:6-9.6 (Sicinska et al., 2007). It has to be mentioned that the historical diagnosis in this case was also Spiegler tumor. This could imply that the diagnosis was based on histopathological examination at the time of this specimen's acquisition, as indeed some of the tumors appear to be incised.  (Ramsing et al., 1990;van Haelst et al., 2007). Sporadic microgastria-limb reduction defects association (MRDA) (OMIM 156810) could pose a plausible differential diagnosis. MRDA is characterized by often asymmetric limb defects including phocomelia and oligodactyly, shrunken abdomen (due to microgastria, hypo-/a-splenia, and renal dysplasia/agenesis) as well as by anophthalmia and cryptorchidism (Shah et al., 2020).

| Case 10. Harlequin ichthyosis with bilateral cleft lip and palate
Specimen MN10.666 and its accompanying wax model concern a male neonate formerly described as being affected with "ichthyosis congenita" (Figure 14). External inspection revealed the typical appearance of autosomal recessive congenital ichthyosis 4B (ARCI4B) also known as harlequin ichthyosis (OMIM 242500), with its fish-like scaling and deeply creased skin (Kelsell et al., 2005). In addition, ectropic eyelids, eclabic lips and a small nose, is observed. A sloping forehead, hypertelorism and low-set small dysplastic ears represent However, in NLS microcephaly and growth delay are more severe, the eye globes are strikingly protruding partly due to malformed or absent eyelids and most NLS fetuses are severely hydropic with typical "puffy hands and feet." Therefore, we remain with the diagnosis of a Harlequin ichthyosis. We diagnosed Harlequin ichthyosis in four other neonatal specimens.
5.11 | Case 11. Hydrolethalus syndrome MN33.148/408 concerns a grossly deformed male neonate (date unknown) formerly described as being affected by hydrocephaly and a facial cleft (Figure 15a). In addition to the severely enlarged head (due to severe prenatal onset hydrocephaly), and pseudomedian cleft lip and palate in the absence of a premaxilla, we encountered a malformation of the eyes suggestive of micro-or anophthalmia, a notched lower lip, preauricular skin tags (Figure 15b) (Hartill et al., 2017). Although a cleft lip/palate represents an inconsistent but commonly co-occurring feature (Paavola et al., 1995).
In another specimen, MN32.808/9, concerning a full-term female neonate that was registered as being affected with a median cleft lip, exencephaly, polydactyly and a "cleft" of the abdomen 5.13 | Cases 14 and 15. Osteogenesis Imperfecta type III or VIII Specimens MN3588 and MN4528 concerns the macerated and dried skeletons of two sisters who died in 1877 and 1885 at the age of 19 and 25 years respectively. They were formerly described as being affected by rickets ( Figure 18). Historically, the coined term rickets was applied on a multitude of skeletal malformations that included bowing of the extremities. Indeed both skeletons showed severe short stature with gross asymmetrical bowing of the tubular bones and metaphyseal expansion. Interestingly, Beighton et al. described these two particular specimens and concluded both actually were rachitic (Beighton et al., 1993). The sisters were said to have been suffering from pulmonary tuberculosis and were locked up in darkness for many years because sunlight was considered to aggravate 5.14 | Cases 16 and 17. Roberts-SC phocomelia syndrome Specimen MN3163 concerns a male neonate, historically described as being affected with phocomelia and cleft lip; acquired around 1870 ( Figure 19a). On examination, a hydrocephaly, bilateral cleft lip/palate, micrognathia, hypertelorism, downslanting palpebral fissures, hypoplastic nasal alae and low-set ears were noticed. Severe reduction defects of the limbs are present with oligodactyly and partial syndactyly of the hands (three digits each) and with the feet being almost directly attached to the pelvic girdle ( Figure 19b). Lastly, a prominent phallus was noticed.
Another specimen in which the same diagnosis was made  (Smith et al., 1964) which was confirmed by the detection of decreased cholesterol values in skin and soft tissues by a previous biochemical cholesterol analysis (Schoner et al., 2020). Unfortunately, pathognomonic accumulation of 7-dehydrocholesterol levels are undetectable in old museal specimens as these degrade under the influence of light (Oostra et al., 1997). However, we do feel that decreased levels of total cholesterol together with the found phenotype is highly susceptive for Smith-Lemli-Opitz syndrome.
In addition to this neonatal specimen, we found a preparation of four extremities in which the same configuration of postaxial hexadactyly of both hands and 2/3 syndactyly of both feet are seen. Although only the extremities of this case have been preserved, subtle facial dysmorphological characteristics-and in case of male sex hypospadias-were perhaps not noticed during initial examination, as the specific morphology of hands and feet is again very suspicious for Smith-Lemli-Opitz syndrome (Kelley & Hennekam, 2000;Waterham et al., 1998). 5.17 | Case 20. Thanatophoric dysplasia type 1 Specimen MN2907 concerns a dried neonatal skeleton in which severe short-limbed dwarfism is noticed (Figure 22a). On examination, we recognize a bell-shaped narrow thorax, short ribs, disc-like thoracic vertebral bodies, squared iliac wings, short, broad and slightly bowed long bones with femoral "telephone receiver deformity" and with small face and low-set ears, a constricted thorax, distended abdomen and outward rotation of the feet (Figure 22b). Although no additional radiological examination was performed to ensure absence of the telephone receiver configuration of the femora, characteristic for TD1, the overall phenotype of the specimen is highly suggestive of thanatophoric dysplasia type 2 (OMIM 187601) (Zhou et al., 2015).  with a bifid nose. This specimen is mentioned here as it is rarely seen that frontal encephaloceles disrupt the face so dramatically. Despite its often lethal neonatal outcome, a skull (MN-2939) from a 42-yearold women formerly diagnosed with "hernia cerebri anterior" was found dated 1864 ( Figure 26b). On examination, this peculiar skull showed pseudohypertelorism, grossly deformed orbits and nasal bones located at maxillary levels with profound underdevelopment of the maxilla and alveola creating prognathism of the mandible. The most striking aspect in this skull is the medially located opening between the two orbits, just above the nasal bones which is the herniation point of the brain. The encephalocele "pushed" the nasal bones caudally and widened the distance between the medial orbital walls creating the pseudohyperteloric appearance (Jackson et al., 1983).

| Case 22. Treacher Collins syndrome
What makes this case rather unique is its presence in an adult skull.
The etiology of frontoethmoidal encephalocele should be sought in defective formation within the nasofrontal region when the temporary fonticulus nasofrontalis (gap between the nasal bones and frontal bone during embryological development) and prenasal space should close and form the foramen cecum (a channel that passes through the midline of the ethmoid roof anterior to the crista galli) with projection of the dural diverticulum at the tip of the nose. When this dural diverticum does not retract and prenasal space lacks obliteration, a situation is created that would encourage the formation of frontal defects such as frontoethmoidal encephaloceles (Hoving, 2000). Indeed, all subtypes of frontonasal/ethmoidal defects are characterized by a bony defect in the midline at the level of the foramen cecum (Marshall et al., 2017). CT (Figure 27d,e) revealed absence of the pleural cavity, heart and lungs although difficult to interpret due to limited contrast. The thorax was filled with a homogenous mass, that corresponds to a gelatinous mesenchymal tissue, as generally observed in acardiac fetuses.

| Case 28. Pygopagus conjoined twins
Specimen MN4002 concerns a wet taxidermy specimen ( Figure 28a) and dried extracted skeleton (Figure 28b) of conjoined twins originally collected by prof. Joseph Hyrtl (1810-1894) (Hyrtl, 1869). The reason to recall this specimen here is its rarity but also its alleged etiology.
This specimen can be interpreted as pygopagus conjoined twins; oftentimes included in the spectrum of symmetrical conjoined twins (Spencer, 2003). However, this type should be included in the dorsal conjunction group as its etiopathogenesis is believed to be different from the standard set of ventral, lateral and caudal conjunction types; . All dorsally united twins (cranio-, rachi-, and pygopagus) show individual internal organs and four sets of extremities, they lack gross underdeveloped regions or dysmorphologies and always show two separate umbilical cords; it is this latter peculiarity that discriminates the dorsally conjoined group from the non-dorsally united twins and defines its different etiology. Morphological investigation of these "known but rare" anomalies could potentially help elucidate the suspected aberrant etiopathogenesis of this type of twinning (Boer, Schepens-Franke, et al., 2021;Oostra et al., 2022).

| DISCUSSION
This article describes and classifies 28 teratological pinnacles from the Narrenturm collection in Vienna and shows the broad phenotypic spectra and syndromic patterns of the conditions encountered during our survey. Examining teratological specimens in a museal setting is beneficial for the museum itself, as collections are (scientifically) used and therewith catalogued and communicated to the public and become contemporary by doing so. Additionally, studying teratological collections has its reflection on the medical community. By studying the many, often extremely rare anomalies and the "unknowns" that are found in any museal collection, morphological spectra can be extended and may aid to better understand clinically encountered conditions. By investigating these-often neglected-collections, novel anomalies, varying manifestations and parallel patterns from (other) anomalies can be etiopathogenetically "conquered." Moreover, focusing on gross morphology and interlinking different specimens could potentially be the beginning of novel clinical entities. Due to the oftentimes limited access to museum specimens efforts are increasingly directed to increase their visibility, for example through online distributions that even include extended reality modalities (Mikami et al., 2022). What makes teratological collections worth examining, apart from the wide phenotypic range of the encountered conditions, are the late stages of maldevelopment, especially the sequential changes they present, as prenatal assessment was absent during the times these specimens were collected. As we have shown here, it is in a number of cases possible to classify the presented conditions syndromologically by external examination only. These diagnoses do however have a tentative status as additional diagnostics were unavailable, or simply impossible, to perform on all described cases. However, as we have shown additional use of radiological imaging and e.g. histology could benefit their (differential) diagnoses. In addition, one of the major hurdles to overcome, and also one of the biggest drawbacks in museal research, is that most of specimens were stored for decades or even centuries in preservation fluids that have such deleterious effects on the DNA that molecular confirmation of a clinical diagnosis is virtually impossible. Additional diagnostics are therefore largely restricted to imaging procedures, since they do not damage the specimens. Besides a wealth of common and rare congenital anomalies, a substantial number of skeletal dysplasias are present within the extant collections. Interestingly, in the past, multiple specimens in the Narrenturm collection were already researched with both radiographs and magnetic resonance imaging (Beighton et al., 1993(Beighton et al., , 2005Pumberger et al., 2003;Rehder et al., 2018), indicating the open attitude to perform additional diagnostics on museal specimens, a premise which is not always obvious or possible. Although the clinical characteristics sometimes permit diagnostic speculation in (neonatal) bone dysplasias, the recognition of distinctive radiographic changes remains the prime method to the establishment of a firm diagnosis, as was done within this report. Finally, in a number of cases the only known specimens of a particular anomaly are the ones present in a museum. These archives of human origin thereby become a sort of "physical database" for rare anomalies which were described in the past. This premise creates a curious historical feedback loop in which current researchers use a modern dysmorphological approach on malformations to confirm historically derived diagnoses of the same specimens that once helped an earlier researcher produce a systematic science of malformations (Ray, 2022). This reassessment demonstrates the persistence of teratology's foundational methods: searching in museal collections with specimens that remain rare and compelling to scientists to be shared, observed and described no matter in which decade we live.

| CONCLUSION
This article provides a glimpse of the extensive collections present in the Narrenturm and describes some rare (syndromic) conditions. Furthermore, this article testifies to the sheer heterogeneity that is encountered in the field of congenital anomalies and demonstrates that museal specimens can be a source for novel observations concerning types and syndromal or sequential patterns of congenital anomalies.

AUTHOR CONTRIBUTIONS
Lucas L. Boer has made substantial contributions to conception and design, acquisition of data, analysis and interpretation of data. Has given final approval of the version to be published and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Susanne Gerit Kircher, Helga Rehder, Jana Behunova, Eduard Winter, Helmut Ringl, Anke Scharrer, Elke de Boer have been involved in drafting the manuscript or revising it critically for important intellectual content. Roelof-Jan Oostra has made substantial contributions to conception and design, acquisition of data, analysis and interpretation of data.

We thank Verena Hofecker, Charlotte Fuchs-Robetin and Roman
Haselbacher for making the pictures of the Narrenturm collection.