INTRODUCTION

Mutilating keratodermas represent a heterogeneous group of rare dermatoses, clinically characterized by progressive digital constrictions that can lead to spontaneous auto amputation [1,2]. In the Sahel area, their diagnosis poses a significant challenge in daily practice due to their similarity to aïnhum, or spontaneous dactylolysis. Indeed, aïnhum is characterized in its early stages by a rare, chronic, and idiopathic fibro constrictive dermatosis. It affects individuals of both sexes of African descent from intertropical regions, with an age between 20 and 50 years [3–5]. It is endemic in sub-Saharan Africa, particularly in Benin [6], Burkina Faso [7], Cameroon [8], and Niger [9]. Most often, aïnhum is characterized by a progressive, unilateral or bilateral fibrous growth ring located on the fifth toe and progressing to auto amputation [3,7–9]. Aïnhum should be distinguished from pseudoainhum, an acquired growth dermatosis that is much rarer. Its overall incidence is exceptional, with only a few reported cases [3]. Unlike aïnhum, pseudoainhum does not show any ethnic or geographic predilection. It occurs at any age, without distinction of sex. It manifests as a circumferential growth groove or ulceration, which may affect the fingers and/or toes [3,4]. Its etiologies are multiple: genetic diseases (palmoplantar keratodermas, ichthyosis, congenital pachyonychia), acquired conditions (chronic infections, peripheral neuropathies, vascular diseases), or iatrogenic causes (mechanical restrictions) [3,4,10–12]. Among genetic causes, Vohwinkel syndrome (mutilating palmoplantar keratoderma of the Vohwinkel type) occupies a special place. It is an autosomal dominant disorder characterized by a clinical triad: diffuse palmoplantar keratoderma, progressive digital constrictions (pseudoainhum), and sensor neural hearing loss [13–15]. Two forms are distinguished: the classic form, linked to mutations in the GJB2 gene, which codes for connexin 26, and the loricrine variant, which is associated with mutations in the LOR gene and is generally devoid of hearing loss [13,15]. Vohwinkel syndrome remains a very rare disease, with a limited number of cases reported worldwide, particularly in Africa. In a Sahelian context, the coexistence of an aïnhum (a type of encephalopathy) and a rare genetic disorder such as Vohwinkel syndrome can lead to potentially serious consequences: diagnostic delays, delayed treatment, and social stigmatization related to erroneous cultural interpretations. We report the case of a 27-year-old Nigerian patient illustrating these difficulties and their consequences.

CASE REPORT

This was a 27-year-old female patient of Djerma ethnicity, originally from a village in western Niger. A housewife, she was referred to the Dermatology-Venereology Department of the Niamey National Hospital for moderate plantar pain while walking, which had been present for eight months. Her medical history revealed bilateral hearing loss dating back to childhood, and a history of bilateral aïnhum with spontaneous amputation occurring five years prior in the right foot and three years prior in the left. She had no personal history of diabetes, gout, alcoholism, or trauma; however, she reported a family history of plantar keratoderma unrelated to aïnhum. Dermatological examination revealed rudimentary scarring of the two fifth toes, a deep circular constrictor groove of the right third and fourth toe and the left fourth toe (pseudoainhum) (Fig. 1). We noted a pronounced bilateral fissured palmar keratoderma (Fig. 2a) and plantar keratoderma (Fig. 2b). The whole was associated with stellate plaques on the dorsum of the feet (Figs. 1a and 2b), and diffuse xerosis. Neurological examination revealed hypoesthesia over the pulp of the toes affected by the grooves. Otolaryngological and ophthalmological examinations were normal. The remainder of the clinical examination of the other organ systems was unremarkable. Paraclinical investigations, radiographs of both feet, showed early bone lysis at the base of the proximal phalanges of the toes with active grooves. The audiogram revealed hearing loss bilateral asymmetric neurosensory (Fig. 3 audiogram tracing).

	Figure 1: Pseudoainhum of the 3rd and 4th right toes and 4th left toe.
	Figure 2: (a and b) Palmar Keratoderma.
	Figure 3: Audiogram tracing.

The biological tests performed (complete blood count, blood glucose, liver and kidney function tests, uric acid, serum electrolytes, HIV serology, hepatitis B and C serology, and syphilis serology) were normal. Vohwinkel syndrome was suspected based on the clinical triad: palmoplantar keratoderma, digital constriction (pseudoainhum), and bilateral sensor neural hearing loss (confirmed by the audiogram). Surgical intervention (Z-plasty of the sulci) was proposed but refused by the patient. Symptomatic treatment was then initiated: a level II analgesic, a body emollient, and a keratolytic agent (10% salicylic acid). Eighteen (18) months after the initial consultation, the patient returned to a state of psychological distress related to a divorce. Her husband and those around her attributed the self-amputation to mystical beliefs. She described a reddish, hemorrhagic, and painful tumor on her left foot that had been developing for two months. Dermatological examination revealed, in addition to the previously observed lesions, a tender, hemorrhagic, fleshy, budding mass (botryomycoma) in the third interdigital space of her left toe (Fig. 4). X-rays showed no bone lysis of the fourth left toe (Fig. 5); however, the complete blood count revealed moderate normocytic normochromic anemia (Hb = 10.4 g/dL). The final diagnosis was Vohwinkel syndrome complicated by botryomycoma and moderate anemia. Treatment included level II analgesic, electrocoagulation of the budding mass, reconstructive surgery of the pseudoainhum of the fourth toe, and supportive psychotherapy.

	Figure 4: Botryomycoma of the 3rd left interdigital space (evolutive complication).
	Figure 5: X-ray shawed no evidence of bone destruction in the fourth digit.

DISCUSSION

This observation has several limitations: the lack of genetic confirmation (unavailable), the absence of a thorough family history, and the loss to follow-up after the initial consultation. Nevertheless, the richness of the clinical picture, as well as the rarity of the reported complication, justifies the interest of this observation. Vohwinkel’s syndrome belongs to the group of hereditary palmoplantar keratodermas. Its classic form is linked to mutations in the GJB2 gene, which codes for connexin 26 (a junction protein expressed in the epidermis and cochlea). These mutations disrupt intercellular exchanges and impair both keratinization and auditory transmission [13,16]. Clinically, the triad is characteristic: diffuse palmoplantar keratoderma, pseudoainhum, and sensor neural hearing loss. Other cutaneous signs, such as star-shaped plaques on the knees, elbows, or backs of the hands and/or feet, are possible but inconsistent [13,14]. In the Sahel, the high prevalence of idiopathic aïnhum often leads to these syndromic forms being overlooked. However, signs such as involvement of toes other than the fifth toe, bilaterality and symmetry of the lesions, a family history, and especially associated signs (keratoderma, deafness, ichthyosis, nail abnormalities) should raise suspicion of pseudoainhum [3,4,10]. Our case confirms the need for a thorough history and a complete clinical examination in any case of digital constriction, even in endemic areas.In our patient, the diagnosis of Vohwinkel was based on clinical arguments [15]: triad of lesions (diffuse palmoplantar keratoderma, pseudoainhum and neurosensory deafness confirmed by the audiogram tracing) as well as the star-shaped plaques on the backs of the feet.

From a paraclinical standpoint, Vohwinkel syndrome is caused by mutations in the GJB2 gene. Molecular confirmation offers several advantages: diagnostic confirmation, family screening, and genetic counseling; however, in the context of limited resources, these tests are often unavailable [15,17]. In our patients, the diagnosis remained clinical and audiometric, based on the characteristic clinical triad due to the lack of a genetic research laboratory [15]. Vohwinkel syndrome belongs to a group of genetic syndromes sharing the association of sensor neural hearing loss and skin abnormalities, whose phenotypic spectrum can overlap, sometimes making differential diagnosis challenging [18]. Among the syndromes linked to mutations in the GJB2 gene encoding connexin 26, Bart-Pumphrey syndrome is distinguished from Vohwinkel syndrome by the absence of pseudoainhum and the presence of total leukonychia and keratosis over the joints. Although she shared the same bilateral sensor neural hearing loss, the absence of these nail and joint signs in our patient allowed us to rule it out [15,19]. KID (Keratitis-Ichthyosis-Deafness) syndrome, also linked to GJB2 mutations, is associated with severe corneal keratitis and generalized ichthyosiform erythroderma, which carries a risk of squamous cell carcinoma. The absence of any ophthalmological involvement and generalized ichthyosis in our patient allows us to eliminate this diagnosis [20]. At the level of mutations in the GJB6 gene encoding connexin 30, Clouston syndrome is characterized by palmoplantar keratoderma, diffuse hypotrichosis, and severe onychodystrophy, without deafness. The absence of these nail abnormalities allows for its exclusion [15,21]. The loricrine variant of Vohwinkel syndrome, linked to mutations in the LOR gene, warrants discussion. It shares the palmoplantar keratoderma and digital constrictions of the classic form; however, the absence of deafness and generalized ichthyosis distinguishes it. In our patient, the presence of sensor neural hearing loss progressing since childhood and the absence of generalized ichthyosis point toward the classic form [16]. Finally, the distinction with idiopathic aïnhum, the initial diagnosis, deserves emphasis. Idiopathic aïnhum almost exclusively affects the fifth toe, unilaterally or bilaterally, without associated deafness or palmoplantar keratoderma. In our patient, three factors retrospectively allowed for this diagnosis at the first consultation: involvement of several toes beyond the fifth, pronounced fissured palmoplantar keratoderma, and bilateral sensor neural hearing loss progressing since childhood [3,4]. The appearance of a botryomycoma (pyogenic granuloma) in an interdigital space in a case of progressive pseudoainhum is exceptional and has not been described in Vohwinkel syndrome. Botryomycomas are benign reactive vascular proliferations, often occurring in areas of micro trauma, chronic inflammation, or maceration [22]. In our case, several factors may have contributed to this complication: interdigital maceration related to keratoderma, narrow interdigital spaces, and repeated micro trauma from walking barefoot. Chronic bleeding led to normocytic anemia, a classic complication of botryomycomas [23]. Other complications are reported in the literature, including squamous cell carcinomas in areas of chronic keratoderma or constriction [24]. This complication illustrates the consequences of delayed treatment of pseudoainhum and justifies the urgency of surgical intervention.

The therapeutic management of Vohwinkel syndrome is multidisciplinary [25–27]: – Medical treatment: Topical keratolytics (salicylic acid, urea) improve keratoderma. Systemic retinoids (acitretin) can slow the progression of constrictions, but access is limited in sub-Saharan Africa. – Surgical treatment: Release of the sulci by Z-plasty is recommended to prevent amputation. In cases of necrosis or spontaneous amputation, a planned amputation may be necessary. – ENT management: Early hearing aid fitting is essential to prevent speech delay and social isolation. Our patient initially refused surgery, probably out of fear or fatalism, before partially accepting it during the second consultation after the onset of pyogenic granuloma and the loss of the other toes. Another important aspect in our observation is the cultural interpretation of the mutilations. The patient was rejected by her community, who attributed self-amputation to mystical causes (curses, witchcraft). This phenomenon is common in sub-Saharan Africa for chronic disfiguring or disabling illnesses; this situation exacerbates the psychological burden and delays seeking care. Supportive psychotherapy is necessary for comprehensive management [28].

CONCLUSION

Our observation underscores the importance of not relying solely on a diagnosis of aïnhum for any digital constriction in endemic areas, and of systematically searching for associated signs (keratoderma, deafness) suggestive of a genodermatosis such as Vohwinkel syndrome. It also highlights the need for close monitoring to detect potential tumor complications (botryomycomas, carcinomas). Finally, in the African context, it sheds light on the impact of cultural representations on the experience of the disease and the necessity of a comprehensive approach integrating psychological and social dimensions.

REFERENCES

1.  Weinberg RL, Coulombe PA, Polydefkis M, Caterina MJ, Pain mechanism in hereditary palmoplantar keratodermas. Br J Dermatol. 2020;182 543-51.

2.  Schiller S, Seebode C, Hennies HC, Giehl K, Emmert S. Palmoplantar keratoderma (KPP):acquired and genetic causes of a not so rare disease. J Dtsch Dermatol Ges. 2014 12:781-8.

3.  Morand JJ, Lightburn E. Aïnhum and Pseudoaïnhum:clinical overview and etiopathogenic hypotheses. Med Trop (March). 2002;62:166-70.

4.  Ogunbiyi AO, Owoaje ET, Olumide YM. Aïnhum and pseudo-aïnhum:a report of two cases. West Afr J Med. 2011;30:435-7.

5.  Kitembo FM, Sangwa MC, Kakinga ZM, Mutomb JF. Aïnhum disease (spontaneous dactylolysis):a clinical case report. Pan African Med J. 2014;19:60.

6.  Koudoupko C, Bourrat E, Rausky J, Yédemon H, Bagot M, Blanchet-Bardon C et al. Aïnhum and African acral keratodermas:three cases. Ann Dermatol Vénéréol. 2015 Mars;142 (3):170-5.

7.  Ouédraogo AN, DakouréPWH, Ndiaye M, Zeba/Lompo S, TraoréF, Tino S, et al. Aïnhum:Clinical, radiological, and therapeutic aspects of 3 cases. Our Dermatol Online 2016;7:453-8.

8.  Tchouakam DN, Tochie JN, Guifo ML, Choukem SP. Ainhum, a rare mutilating dermatological disease in a female Cameroonian:a case report. BMC Dermatol. 2019;August 12;19 (1):12.

9.  Idrissa SM, Dalatou MMMH, Abdoul Wahab MA, Niandou MA, Soumana YI, Souna BS. Ainhum in the Sahel region:3 cases and a literature review. HealthSci Dis. 2023;24:129-31.

10.  Behera B, Cochhalt D, Thappa DM. Pseudo-ainhum and autoamputation associated with lamellar ichthyosis. Indian J Dermatol VenereolLeprol. 2017;83:728-9.

11.  Turan E, Yesilova Y, Kokgil T, Guvenc U. Pseudo-ainhum in a patient with tuberous sclerosis complex:a case report and review of the literature. Int J Dermatol. 2014;53:357-61.

12.  Akallal N, Belgnaoui FZ, Benameur H, Afifi Y, Senouci K, Birouk N, Yahyaoui M, Hassam B, Pseudo-ainhum and axonal neuropathies. Ann Dermatol Venereol. 2006;133:791-4.

13.  Sinha M, Watson SB. Keratoderma hereditarium mutilans (Vohwinkel syndrome). J Hand Surg Eur Vol. 2009;34:235-7.

14.  Ul Bari A. Keratodermie hereditarium mutilans (Vohwinkel syndrome) in three siblings. Dermatol Online J. 2006 Dec 10;12 (7):10.

15.  Anilkumar S, Thomas I.N, Sukumaran V. Early diagnosis of Vohwinkel syndrome-inherited honeycombed hands and hearing loss. Int J Adv Med. 2024;11:408-10.

16.  Montero-Vilchez T, Martinez-Lopez A, Rodriguez-Tejero A, Salvador-Rodriguez L, Garcia-Dura E, Molina-Leyva A, Arias-Santiago S. loricrin keratoderma:description of a novel mutation, systematic review and meta-analysis between genotypic and phenotypic characteristics. J between genotypic and phenotypic characteristics. J Dstch Dermatol Ges.2020;18:1316-21.

17.  Has C, Technau-Hafsi K. Palmoplantar Keratodermas:clinical and genetic aspects. J Dsch Dermatol Ges. 2016;14:123-39;quiz 140.

18.  Sakiyama T, Kubo A. Hereditary palmoplantar keratoderma ”clinical and genetic differential diagnosis”. J Dermatol.2016;43:264-74.

19.  Al-Hamdi KI, QaisSaadoon A, Abduljabbar NH. Bart Pumphrey syndrome. JAMA Dermatol.2020;156:1126.

20.  Cammarata-Scalisi F, Willoughby CE, Cardenas Tadich A, Labrador N, Herrera A, Callea M. Clinical, etiopathogenic and therapeutic aspects of KID syndrome. Dermatol Ther.2020;33:e13507.

21.  Ahmed C, Trope BM, Amorim G, Ribeiro M, Ramos-E-Silva M. Clouston Syndrome. Skinmed. 2021;19:54.

22.  Mahjoub A, Zaafrane N, Chaabene R, Ben Abdessiem, Sellem I, Allagui O, et al. pyogenic Granuloma:Clinical, etiological and therapeutic characteristics. A series of five cases. J Fr Ophtalmol.2023;46:e230-e233.

23.  Castela J, Mao de Ferro S, Ferreira S, Cabrera R, Dias Pereira A. Pyogenic granuloma of the jejunum:an unusual cause of anemia. J Gastrointest Surg.2018;22:1795-96.

24.  Yang Hi-Dan, Jiang Juan, Xu Xiu-Lian. Squamous cell Carcinoma Secondary to mutilating Palmoplantar Keratoderma. Int JDermatol Venereol. 2019;2:236-40.

25.  Bell M, Hoede N, Schopf RE. Pseudo-ainhum in Vohwinkel disease. Keratoma hereditarium mutilans. Hautarzt. 1993;44:738-41.

26.  Bassetto F, Tiengo C, Sferrazza R, Belloni-Fortina A, Alaibac M. Vohwinkel syndrome:treatment of pseudoainhum. Int J Dermatol.2010;49:79-82.

27.  Bonvillain KW 2^nd, Rees AB, Drexellius KD, Serbin R, Aversano Mw, Gaston RG. Long-term surgical Success in treating Vohwinkel Syndrome. A report box. JBJS Case Connect.2024;14. doi:10.2106/JBJS.CC.24.00251.

28.  Dimitrov D, Szepietowski JC. Instruments to assess stigmatization in dermatology. PostepyHig Med Dosw (online). 2017;71:901-5.