A Boy with an Itch: A Case Report of Genital Nodular Scabies

Abstract

Scabies is an enormous global public health problem and one of the World Health Organization’s 20 most neglected tropical diseases. Scabies affects all groups with children and elderly, particularly in resource scarce countries, among the most vulnerable in terms of prevalence, morbidity, and preventable sequalae. The medical community now recognizes the preventable life-threatening secondary complications attributable to scabies. Nodular scabies occurs in more than 10% of patients despite successful treatment of primary scabies and is particularly easy to misdiagnose. We report a case of nodular scabies in a 6-year-old child. He presented with severe deformity to the head of the penis and severe pruritis lasting for many months. Our case highlights the importance of understanding the differences in disease pathophysiology between scabietic infestation and hypersensitivity to its retained products to better direct effective treatment. Proper diagnosis and treatment of nodular scabies will undoubtedly curb secondary complications on a global scale.

Introduction

Scabies infestation is a global public health problem, affecting people of all ages, races, and socioeconomic groups. In industrialized countries, scabies outbreaks occur primarily in institutional settings, such as prisons and long-term care facilities, including hospitals and nursing homes.^1,2 Despite being severely underreported, prevalence rates for scabies in developing nations are much higher than those in industrialized countries. ³ Approximately 300 million cases of scabies are reported worldwide each year. Conditions and circumstances that increase global poverty and overcrowding are associated with increased transmission rates; at the top of this list are natural disasters and war. ⁴

A scabies rash typically appears 4 to 6 weeks after initial infestation with the Sarcoptes scabiei mite. A well detailed patient history can reliably suggest the presence of scabies, though definitive diagnosis of infestation depends on identification of mites, eggs, or feces in skin scrapings or biopsies. Intractable pruritus, which is worse at night and commonly affecting more than one family member should immediately rank scabies at the top of the clinical differential diagnosis. Common lesions are papules, vesicle, and pustules. The pathognomonic sign however is the burrow which can be described as a short, wavy, scaly, gray line (described as “jet with contrail”) typically found between the webbing of fingers and toes. One may also notice widespread linear excoriations due to the intense, unbearable pruritis. Scabies of the genitalia can provoke intense itching along with formation of tiny, raised pimple-like bumps on and around the penis and scrotum.

Case Report

A 6-year-old boy presented to pediatric clinic in a camp for internally displaced people (IDPs) in northern Iraq with the chief complaint of a pruritic penis. He was accompanied by his mother who accounted for the history via translation by the clinic’s interpreter. She stated that the pruritis has been there for many months and was localized to the head of the penis, which now shows significant deformity. Neither pruritis nor deformity was apparent on the shaft or testicles. The boy’s compulsion to relieve the pruritis intensified over time whereby he began to scratch himself constantly. His past medical history was unremarkable, though the patient’s mother explained that the child was diagnosed with scabies 8 months earlier and successful eradication consisted of treatment with topical scabicidal cream (permethrin 5%). Between that first visit to the time I saw him in clinic, the patient was seen 3 other times for the same presentation and prescribed: a topical antifungal (clotrimazole 1% cream), a topical corticosteroid (betamethasone 0.1% cream) as well as calamine lotion. These visits occurred over the course of approximately 3 to 4 months, none of which brought any long-lasting relief if any at all.

According to the mom, her son’s biggest concern and most severe symptom is still this uncontrollable itch of his now marred penis. History was negative for urethral discharge, dysuria, and trauma to the region. Vaccinations were up to date, and there were no known drug allergies. He has one older brother that he shares a mattress with and no one else in the family unit complained of pruritis or rash.

On examination, vital signs were normal, the abdomen was soft and negative for organomegaly. The penis was circumcised and both testicles were descended. The shaft of the penis and testicles were unremarkable and normal in size for age. The urethral orifice was in normal position and no discharge was noted. The glans penis and prepuce area showed significant inflammatory keratinization and multiple erythematous nodular lesions of variable sizes seen (Figure 1). Some superficial excoriations were also noted. Inguinal lymph nodes were not palpable. Also evident were erythematous papules and papulovesicular lesions on the ventral and dorsal surface of the wrist and in the interdigital web spaces mostly between the thumb and index fingers (Figure 2).

Figure 1.

Dermatosis of the penis showing considerable inflammatory dermatitis, nodular lesions, and chronic scarring leading to deformity.

Figure 2.

Papular and papulovesicular lesions on the dorsal surface at the base of the first metacarpal and thenar webspace (arrows).

Discussion

Scabies infestation is caused by the female mite Sarcoptesscabiei var. hominis. ⁵ (Greek word “sarx” meaning flesh and “koptein” meaning to smite or to cut and the Latin word “scabere” meaning scratch). The mite is an ectoparasite and cannot live free of host for longer than 2 to 3 days and cannot withstand temperatures > 50°C for longer than 10 minutes. Since life in a refugee camp follows the golden rule of “everything has value” and therefore rarely allows for the discarding of contaminated possessions such as mattresses and linens. Special instructions were followed to decontaminate the child’s bed, clothes, and towels. Established protocols require washing contaminated objects in hot water followed by drying in the hot sun or sealing contents in plastic bags for 72 hours for thermal sterilization before implementing for re-use is standard protocol.^6,7

Transmission can spread quickly primarily via skin-to-skin contact and is highly contagious, though the notion that humans can acquire the infection from animals including dogs has now been widely disproven.^8,9 Infrequently, it may be acquired through contact with infected clothing and bedding, but this is a less common route of infestation in developed countries since the mite is only able to survive away from its host for 2 to 3 days at most. ⁶ With communal beds and bed sharing being standard practice, this route of infestation transfer appears to be a much more prevalent in refugee camps.

Nodular scabies (NS) is a severe form of scabies that occurs in approximately 10% of patients, particularly young children. It typically presents as persistent pruritic nodules that may last for months even after successful treatment and eradication of scabies infestation has occurred. ¹⁰ Penile and scrotal skin seem to be the most common sites for nodular lesions which are typically pinkish brown lesions ranging from 2 to 4 mm in diameter. ¹¹ Since nodular scabies is considered a hypersensitivity reaction (likely to retained products), treatments appropriately include strong topical immunosuppressants or intralesional steroid injection. Another modality of treatment is twice daily application of topical tacrolimus 0.03% ointment over the affected surface.

Primary scabies rash typically involves burrows that appear as serpiginous, grayish, threadlike elevations in the superficial epidermis, ranging from 2 to 10 mm long. ¹² Intense itching is a hallmark symptom of both classic and nodular scabies infestation. The intense pruritis comes from immune reactions against the mites and/or their products after they have buried themselves under the skin and laid eggs and/or released skybala (fecal pellets). The resultant skin abrasions and lesions are self-inflicted from intense, almost compulsive scratching (like dermatillomania) and secondary infections are commonplace.

The intense pruritis caused by nodular scabies, if misdiagnosed, puts a person at risk for open wounds that never have a chance to heal, essentially functioning as a nidus for secondary infections. In other words open lesions caused by nodular scabies, much like those caused by primary infestation, have similar potentials for serious downstream systemic and even life-threatening conditions. ¹³ Modern day medicine has a greater appreciation of the long-term sequelae of scabies infestation which can lead to other illnesses such as rheumatic heart disease (RHD), acute post-streptococcal glomerulonephritis (APSGN) and even sepsis. ¹⁴ The source of infection that causes acute post-streptococcal glomerulonephritis is quite different in equatorial regions, as the skin, rather than the pharynx, appears to be the main source of infection. In a study conducted in northern Australia, symptomatic acute glomerulonephritis was reported in 10% of children. In addition, 24% of that same population had microscopic hematuria suggesting that asymptomatic renal damage can also occur. The principal source of the post streptococcal glomerulonephritis was closely associated with GAS isolated from secondary skin sores that primarily resulted from scabies infestation induced pruritis. In endemic areas of scabies, infection with streptococci can also occur in the absence of active scabies infestation. It has also been noted that persistent proteinuria can be detected for up to 16 years after the initial infection in 13% of those with recognized post-streptococcal glomerulonephritis versus 4% of controls in an area endemic for scabies-associated infestation. According to a 2013 study, the global burden of scabies is one of the leading causes of skin-related disability-adjusted life years (DALYs) which is a tool used to measure health loss due to a disease or injury. An incredible 1.7 million DALYs is attributable to scabies alone. ¹⁵

In summary, genital nodular scabies is a severe form of scabies that can occur in as many as 1 in every 10 patients successfully treated for primary scabies. Mild symptoms may occur shortly after (days to weeks) the initial scabies rash has been treated successfully. Symptoms usually intensify with time and frank nodules can appear a few weeks to even a few months after the infestation has cleared. The nodules occur because of hyperallergic reactions to parts of the scabies mite that have been left under the skin from the original infection period. Initially, a patient may show prominent nodules that are typically pinkish brown in color and vary between 2 and 4 mm in diameter. The genital areas are the most typical sites for the inflammation to appear and can also be difficult to treat. Treatment is distinctively different from primary scabies in that powerful immunosuppressants are typically required to successfully treat the cell-mediated autoimmune reaction, rather than topical antiparasitic medication required to treat primary scabies.

Conclusion

The ultimate challenge with this case was to put the patient’s presentation into context with environmental risk factors. Similarly, it was also critical to ask about past infestation with scabies. Without doing so, the chief complaint is merely a ruse in that the nodular lesions and deformity may lead one away from making the correct diagnosis. A physician might be more inclined to consider balanitis or balanoposthitis as more likely diagnoses given the inflamed nodular lesions found on the glans penis. On the other hand, if a physician gives more weight to the pruritis and the child’s risk for infestation by living in the unhygienic camp, it is understandable why one might diagnose primary scabies (even in the absence of mites or burrows). Crucial to the diagnosis is to consider the sum of all relevant clues found in history and by exam and to weigh them as a whole. In this case, the index of suspicion for nodular scabies became the most likely diagnosis. The factors that led to the diagnosis of nodular scabies included: a previous diagnosis of primary scabies infestation, lack of any other family member currently being affected, absence of burrows in typical areas of infestation, failed past treatments for primary scabies, and lastly that the pruritus did not intensify at night. Once the diagnosis was made, the treatment consisted of topical tacrolimus 0.03% applied to the head of the penis twice a day for 4 weeks.